Hydraulic Systems Procedures

This page lists 79 maintenance procedures for hydraulic systems, drawn from HIT Srl's internal procedure library extracted from manufacturer service manuals.

HIT Srl supplies hydraulic pumps, valves, cylinders and filtration spare parts for this class of machine.

General guidance only — always follow the operation and maintenance manual for your specific machine.

Hydraulic Cylinders

• What is the correct sequence to trace the source of a hydraulic cylinder leak?

  1. Carefully check the source of the leakage before taking any action; it may be possible to rectify the fault without disassembly.
  2. Check for external leakage at the cylinder end welds, the sleeve coupling welds, and between the cylinder barrel and cylinder head — this could be due to a defective O-ring or damaged O-ring sealing surfaces, both of which can be rectified with the cylinder in place; also check between the cylinder head and piston rod, which could be due to a damaged piston rod or a damaged or worn piston rod seal.
  3. Check for internal leakage by pressurizing the cylinder and checking whether the piston sinks back; this could be due to a worn piston seal.

  Note: Carry out all fault tracing with as low a pressure in the system as possible, since high pressure causes the seals to close tighter, preventing detection of leaks.

• What is the correct sequence to dismantle a hydraulic cylinder for repair?

  1. Remove the cylinder from its mounting and undo the connections.
  2. Plug the cylinder connections and hoses without delay.
  3. If the cylinder is opened, observe the strictest cleanliness.

• How are hydraulic cylinder ball joints greased?

  1. Check the integrity, fastening and seal of the cylinders, unions and pipes, and check that the oil scraper rings on the rods and head show no signs of leaking.
  2. Grease the ball joints at the base of the cylinder and on the rod using the special lubricators.

  Note: Do not grease the rod sliding area.

• What is the correct general sequence for repairing a leaking hydraulic cylinder by replacing its seals?

  1. Remove the relevant hydraulic cylinder and immediately fit protective caps or plugs to the hydraulic cylinder and hose connections.
  2. Take the cylinder to the workshop, drain any remaining oil, and carefully wash the outside of the cylinder.
  3. Dismantle and assemble the cylinder according to the instructions for that particular cylinder type.
  4. Remove all seals and scraper rings, using a screwdriver as shown for the cylinder head seal, and clean all components thoroughly.
  5. Fit the lip seal in the cylinder head with the lip facing inwards towards the piston, oiling it and pressing it in by hand.
  6. Fit the piston seal by hand: fit the centre sealing ring onto the piston first, then the two backing rings and the two guide rings.

  Notes:

  • Never use compressed air for removing the piston from the cylinder; you could sustain serious injuries.
  • Take extreme care when removing the seal in the cylinder head, to avoid scratching the bottom of the groove, since oil leakage will otherwise occur in the future.
  • Do not use tools to press in the lip seal, since even a minute scratch may cause it to leak.

• What is the correct sequence to find the source of a hydraulic cylinder leak?

  High pressure tightens all seals and makes it more difficult to discover a leak.

  1. Carry out all fault finding with the minimum hydraulic pressure required to actually discover the leakage.
  2. Check extremely carefully where the leakage comes from before taking any action, since it may be possible to stop it without costly dismantling.
  3. Check for external leakage: welds on cylinder ends, welds on coupling connections, leakage between the cylinder pipe and cylinder head (a faulty O-ring or damaged O-ring sealing surface), and leakage between the cylinder head and piston rod (a damaged piston rod or worn piston rod seal).
  4. Check for internal leakage between the hydraulic piston seal and the cylinder pipe, due to a worn piston seal, by putting the cylinder under pressure and checking whether the piston sinks back.

• What is the correct sequence to dismantle a hydraulic cylinder for seal inspection?

  Before dismantling, always check that the piston rod is free from any remains of paint, and that there are no burrs or impact damage by the connections or couplings.

  1. Loosen the cylinder from its mounting and loosen the hydraulic connections.
  2. Immediately plug the cylinder connections and hoses/lines.
  3. Open the cylinder observing the highest possible level of cleanliness.
  4. Check the surfaces of all seals and sealing grooves: O-ring grooves (internal and external), piston rod seals in the cylinder head, the sealing groove on the piston, the cylinder pipe surface, the piston rod's chromium-plated surface, and all sliding (dynamic) surfaces.

  Note: When fitting the cylinder head, fit it absolutely straight, preferably by hand; never hit it with a mallet or hammer, since an askew cylinder head can damage the piston rod seal's lip and destroy its sealing function.

• What is the correct sequence to remove a piston rod seal with a screwdriver?

  Applies to single V seals, pre-tensioned V seals with support ring, and compressible seals in the cylinder head. Check the sealing lips beforehand by carefully feeling around the seal with a finger nail, since even the smallest damage to them can cause a major leak.

  1. Insert the screwdriver into the inside of the seal's V shape (or, for a TICLA-type seal, between the inner sealing lip and the intermediate bead) without touching any sealing surface.
  2. Lever the seal out and twist it up to remove it.

  Notes:

  • The screwdriver must only come into contact with the inside of the V shape so it cannot touch and damage a sealing surface; a score from the screwdriver on a sealing surface will have a disastrous effect and cause major leakage.
  • On a TICLA-type seal, insert the screwdriver between the inner sealing lip and the intermediate bead instead, for the same reason.

• What is the correct sequence to remove the wiper from a hydraulic cylinder head?

  The wiper can be removed without dismantling the cylinder.

  1. Carefully tap a screwdriver down between the wiper and the cylinder head, working only against the outer edge of the wiper.
  2. Lever the wiper out.
  3. Polish off any marks left on the cylinder head.

  Note: No tools should be introduced from the inside, as this can score the cylinder pipe, which in turn can damage the piston rod, or damage the piston rod seals when the piston is fitted.

• What is the correct sequence to dismantle a double-action piston seal?

  1. Remove the guide rings and support rings.
  2. Move the sealing body over to one side of the sealing groove.
  3. Press up the material so that there is a gap between the seal and the piston.
  4. Cut the seal off with a knife, without damaging the surface of the piston.
  5. Carefully check the seal for damage that may have caused leakage, by bending over the seal section by section and checking the sealing surface with a finger nail.

  Note: Be very careful when fitting the piston in the cylinder pipe to avoid damage to the seal from the threading in the cylinder pipe, since the whole surface within the cylinder pipe is a sealing surface.

• What is the correct sequence to fit a double-action piston seal?

  1. Fit the middle sealing body first.
  2. Fit the support rings.
  3. Fit the guide rings.

  Note: Fit everything by hand, without tools, in order to prevent damage.

• What is the correct sequence to repair minor damage to a piston rod's chrome surface?

  The smallest damage to a piston rod can be enough to cause leakage; the chromium plating is 20-50 microns thick and can be worked on to repair smaller damage as an alternative to costly dismantling. Sufficient chrome must always remain visible at the point of damage.

  1. Locate the damage with finger tips and finger nails.
  2. Using a small, finely polished panel-beating hammer, work the material in from the area surrounding the damage, working from the outside in towards the damage, until a sharp mark becomes a more even irregularity.
  3. Polish with emery cloth in stages, using grades from 240 to 600, wrapping the cloth around a file for support.
  4. For larger damage: fill the damaged area with a weld, completely remove all welding cinder, file down the weld to the same level as the chrome surface, and polish to an even finish with emery cloth.

• What is the correct sequence to lubricate a single-action hydraulic cylinder that operates over only a limited part of its stroke?

  This type of cylinder has no hydraulic fluid supply on the piston rod side; if it normally operates over only a limited part of the piston stroke, there is a risk of corrosion in the upper part of the cylinder.

  1. Unscrew the breather filter.
  2. Spray 300-500 ml of hydraulic fluid into the filter connection.
  3. Run the cylinder to the limits of the piston stroke a number of times, until no more hydraulic fluid is forced out of the breather filter connection point.

• What is the daily lubrication procedure for all hydraulic cylinders?

  Periodicity: Daily.

  1. Run all cylinders to the piston stroke limit so that the whole of each cylinder is lubricated.

Pumps

• What is the correct sequence to replace a fixed-displacement gear pump?

  1. Put the machine in service position.
  2. Depressurize the hydraulic system.
  3. Clean the hydraulic oil pumps and the area around them.
  4. Mark up and detach the hydraulic hoses from the pump, plugging all connections immediately to protect the hydraulic system from impurities.
  5. Remove the pump: remove the retaining bolts, then pull the pump backwards and lift it away.
  6. Transfer the connection adapters to the new pump, checking that the O-rings are intact and fitted correctly.
  7. Check the pump seals, replacing them if necessary.
  8. Fit the gear pump and axial piston pump, checking that the gear grips the shaft, then fit the pump's retaining bolts, using thread locking fluid to lock the screws and seal the screw holes in the transmission.
  9. Connect the hydraulic hoses according to the markings, checking that the O-rings are intact and fitted correctly.
  10. Turn on the power supply and start the engine.
  11. Check that the hose connections and the seal between the gear pump and axial piston pump are tight.
  12. Check the hydraulic oil level with all hydraulic cylinders fully retracted, topping up if needed.

  Notes:

  • Read the safety instructions for oil before working.
  • Pre-fill the pumps with oil through the pressure connection before taking them into service; if necessary, vent the pumps by loosening the hoses on the delivery side.
  • If the pump is replaced due to malfunction, also change the oil and filter.
  • Overfilling the oil can cause leakage and environmental damage; the hydraulic oil level is checked with all hydraulic cylinders fully retracted.

• What is the correct sequence to check the hydraulic oil pumps?

  1. Operate and warm up the machine so the hydraulic oil reaches operating temperature, approximately 50°C.
  2. Turn off the engine.
  3. Connect a pressure gauge to the pressure connection on hydraulic oil pump 1.
  4. Start the engine and let it idle.
  5. Check the stand-by pressure for one pump at a time, in order (pump 1, 2, 3, 4), comparing against the values on the machine's pressure plate; the pressure difference between the pumps must always be maintained.
  6. Increase engine speed to approximately 1100 rpm and run the extension function against its end-position (overflow), by running the boom out to max and continuing to request max extension with the control lever.
  7. Check the max pressure on hydraulic oil pump 1, comparing it against the pressure plate; all pumps should give the same pressure.
  8. Turn off the engine.
  9. Transfer the pressure gauge to the next pump and repeat the checks on all four pumps.

  Note: Always depressurize the hydraulic systems before starting to work in them; avoid skin contact with the oil, use protective gloves.

• What is the correct sequence to vent the variable hydraulic pumps?

  Settings and venting may be carried out only by authorized personnel, and must be done with the hydraulic system at normal working temperature.

  1. Vent the pumps before the engine is started.
  2. Connect compressed air at a maximum of 0.1 bar pressure to one of the breather filter connections on the hydraulic tank, and plug the other breather filter connection.
  3. Loosen the relevant hoses somewhat from the pump connections.
  4. Tighten the hose connections again once air-free hydraulic fluid runs out.
  5. Empty the accumulators by opening the accumulator evacuating valve.
  6. Start the engine and stop it again to check the stop function.

• What is the correct sequence to set the stand-by, main pressure limitation, and system pressures on the variable hydraulic pumps?

  These settings may be carried out only by authorized personnel, with the hydraulic system at normal working temperature. Skip the main pressure limitation valve steps unless the main valves are being replaced or their seals have been broken.

  1. Start the engine and allow it to idle.
  2. Connect a manometer to each of the four measurement outlets in turn and check the stand-by pressure pump by pump, adjusting the stand-by pressure adjustment screws as needed while maintaining the same pressure differentials between pumps.
  3. If the main valves are being replaced or their seals broken, unscrew fully counter-clockwise the pressure limitation adjusting screws on both inner pumps.
  4. Screw in fully clockwise the corresponding adjusting screws on both main valves.
  5. Connect the manometer to the designated test outlet.
  6. Have an assistant increase engine revs to approximately 1100 rpm and extend the boom fully out until the function is overflowing, keeping it overflowing during the next step.
  7. Screw in the pressure limitation adjusting screw for the inner pump until the manometer reading is 5 MPa higher than the pressure stated on the hydraulic plate.
  8. Unscrew counter-clockwise the adjusting screw on the left main valve until the manometer reading is 3 MPa higher than the pressure stated on the hydraulic plate.
  9. Move the manometer to the corresponding test outlet on the right main valve and repeat the pressure limitation adjustment for the other inner pump and the right main valve.
  10. Connect the manometer to the test outlet for the first pump and overflow the extension function again as before.
  11. Set the system pressure for that pump with its adjusting screw for max pressure, referring to the hydraulic plate for the target pressure.
  12. Move the manometer to the next test outlet and repeat the system pressure setting for that pump.
  13. Repeat the system pressure setting for all four pumps in the same way; all pumps should be set to the same pressure, and the sequence in which they are set is not significant.

  Notes:

  • Immediately shut down the engine if the charging pressure exceeds the pressure stated on the hydraulic plate.
  • The pressure stated on the machine's hydraulic plate for the main valves must be set on the pumps, not on the main valves.

• What is the correct sequence to set the steering pressure and check the accumulator charging and servo pressures?

  These settings may be carried out only by authorized personnel, with the hydraulic system at normal working temperature.

  1. Connect the manometer to the test outlet on the priority valve, turn the steering wheel to maximum wheel deflection, and rev the engine to 1200 rpm; check that the pressure reading corresponds to the hydraulic plate, adjusting with the steering pressure screw if needed.
  2. Allow the engine to idle.
  3. Connect the manometer to the test outlet on the accumulator charging valve.
  4. Close the accumulator evacuating valve.
  5. Check that the accumulator charging starts at 15 MPa and stops at the pressure stated on the hydraulic plate, adjusting with the accumulator charging pressure screw if needed.
  6. Connect the manometer to the servo pressure test outlet and check that the pressure reading corresponds to the hydraulic plate (the servo pressure is not adjustable).

• What is the correct sequence to check the hydraulic oil pump for brakes and steering?

  1. Operate and warm up the machine so the hydraulic oil reaches operating temperature (at least 50°C).
  2. Put the machine in service position.
  3. Depressurise the hydraulic system.
  4. Connect a pressure gauge to the measuring outlet for pump pressure brakes and steering on the main valve.
  5. Start the engine and let it idle.
  6. Close the accumulator drain valve and check the pump pressure during charging, confirming it rises to the specified feed pressure on the pressure plate.
  7. Depressurise the hydraulic system.
  8. Remove the pressure gauge and fit the protective cap on the pressure check connection.
  9. Close the accumulator drain valve, checking it is completely closed and the lock ring tightened.

• What is the correct sequence to check the hydraulic oil pump for load handling?

  1. Operate and warm up the machine so the hydraulic oil reaches operating temperature (at least 50°C).
  2. Put the machine in service position.
  3. Depressurise the hydraulic system.
  4. Connect a pressure gauge to the measuring outlet for pump pressure load handling on the main valve.
  5. Close the accumulator drain valve and the attachment relief valve.
  6. Start the engine and let it idle.
  7. Check that the feed pressure corresponds with the pressure plate.
  8. Turn off the engine.
  9. Depressurise the hydraulic system.
  10. Remove the pressure gauge and fit the protective cap on the pressure check connection.
  11. Close the accumulator drain valve, checking it is completely closed and the lock ring tightened.

Hydraulic Oil Filter

• What is the correct sequence to change the hydraulic oil filter?

  1. Clean the area around the cover plates on the hydraulic oil tank.
  2. Turn off the engine and the main electrical power.
  3. Remove the cover plates over the hydraulic oil filters.
  4. Prepare a receptacle to collect any oil spills.
  5. Lift up the filter unit and place it in the receptacle, letting the hydraulic oil drain.
  6. Part the filter unit and remove the filter cartridge, noting the placement of the parts; handle the cartridge as environmentally hazardous waste.
  7. Clean the filter holder's parts, paying special attention to the magnetic rod.
  8. Fit the new filters and assemble the filter units.
  9. Fit the filter units and the cover plates, tightening the bolts crosswise.
  10. Check the oil level in the hydraulic oil tank with the boom completely lowered and retracted; the oil level should be at the top of the level glass, topping up if needed.

  Notes:

  • Always depressurize the hydraulic systems before starting to work in them; avoid skin contact with the oil, use protective gloves.
  • Ensure cleanliness around the filter and filling point; dirt particles may cause machine damage.

• What is the correct sequence to change the hydraulic oil filter (high pressure filter)?

  1. Put the machine in service position.
  2. Depressurize the hydraulic and brake systems.
  3. Place a receptacle under the oil filters to collect any oil spills.
  4. Clean the outside of the hydraulic oil filters.
  5. Remove the drain plugs in the bottom of the filters and let the oil drain, waiting a while since it drains slowly.
  6. Remove the filter brackets and clean them.
  7. Remove the filter inserts, noting the position of the O-rings.
  8. Fit the O-rings on the filter inserts and filter brackets, lubricating them with hydraulic oil.
  9. Fit the new filter inserts on the filter bracket.
  10. Fit the filter bracket and the drain plug.
  11. Close the drain valve on the accumulator charging valve.
  12. Turn on the main electric power and start the engine.
  13. Check that the filter brackets do not leak.
  14. Remove the receptacle, handling filters and oil as environmentally hazardous waste.
  15. Check the oil level in the hydraulic oil tank with the boom completely lowered and retracted; the oil level should be at the top of the level glass, topping up if needed.

  Notes:

  • Always depressurize the hydraulic systems before starting to work in them; avoid skin contact with the oil, use protective gloves.
  • Ensure cleanliness around the filter and filling point; dirt particles may cause machine damage.
  • The filter brackets are heavy; loosen them carefully.

• What is the correct sequence to change the hydraulic oil fine filter?

  1. Put the machine in service position.
  2. Clean the area around the fine filter.
  3. Remove the cover.
  4. Prepare a receptacle.
  5. Lift up the filter cartridge and place it in the receptacle, letting the hydraulic oil drain.
  6. Fit the new filter cartridge and fit the cover on the fine filter.

  Notes:

  • Always depressurize the hydraulic systems before starting to work in them; avoid skin contact with the oil, use protective gloves.
  • Ensure cleanliness around the filter when working; dirt particles may cause machine damage.

  Confirmed across independent manufacturers’ manuals.

• What is the correct sequence to change the high pressure hydraulic oil filter?

  The filter must be changed at the intervals specified in the lubrication chart, and also whenever work has been carried out on the hydraulic system.

  1. Clean the outside of the filter and the area around it.
  2. Place a vessel under the filter to collect any spillage.
  3. Empty the filter bowl by unscrewing the drain plug.
  4. Unscrew the filter bowl.
  5. Slide off the filter cartridge.
  6. Replace the two O-rings between the filter head and the filter bowl, moistening them with hydraulic fluid before fitting.
  7. Remove the new filter cartridge from its packaging and immediately fit it.
  8. Clean the filter bowl carefully and half fill it with hydraulic fluid.
  9. Screw the filter bowl back into position.
  10. Start the engine to purge the system of air, and check that the filter does not leak.

• What is the correct sequence to change the servo hydraulics filter cartridge?

  Periodicity: Every 1000 hours of operation.

  1. Unscrew the bottom section of the housing and withdraw the cartridge downwards.
  2. Fit a new cartridge, check the O-ring, and refit the bottom section of the housing.

• What is the correct periodicity to change the brake cooling circuit hydraulic oil filter?

  Periodicity: Every 1000 hours of operation (on machines with two filters, change both every 1000 hours).

  1. Change the filter (or both filters, if the machine has the two-filter option).

• What is the correct sequence to change the hydraulic oil filter?

  1. Turn off the engine and turn off the main electric power.
  2. On machines with a raised cab, remove the footstep over the covers and clean the covers and surrounding area.
  3. Remove the cover plates over the hydraulic oil filters.
  4. Lift up the filter unit and place it in the receptacle, letting the hydraulic oil drain.
  5. Part the filter unit and remove the filter insert, handling it as environmentally hazardous waste and noting the position of the parts.
  6. Clean the filter holder's parts, paying special attention to the magnetic rod.
  7. Fit the new filters and assemble the filter units.
  8. Install the filter units and cover plates, tightening the bolts crosswise.
  9. On machines with a raised cab, refit the footstep over the covers.
  10. Check the oil level.

  Note: Ensure cleanliness around the filter and filling point when working on the hydraulic tank; dirt particles may cause machine damage.

• Flushing and cleaning the hydraulic system oil circuit on a quayside container crane

  1. Before filling, filter the hydraulic oil, use clean oil-filling tools, and do not remove the filter at the oil tank entry just to speed up filling.
  2. When removing the oil filling cover, filter cover, inspection holes or oil pipe for maintenance, keep away from flying dust; remove dirt around the tank cover and impurities at the connection point before opening it (do not use water to clean the impurities, to prevent water infiltration).
  3. Use cleaning materials that do not shed fibre impurities, and clean and blow-dry hydraulic elements and hoses before assembling; clean the filter whenever the oil is changed.
  4. Use a cleaning oil of the same type as the system oil, keeping its temperature between 45 and 80 degrees C, and flush with a large oil flow to fully remove impurities. Flush the hydraulic system more than three times, discharging the cleaning oil completely after each flush before it cools down. Before filling new oil, clean the filter and install a new filter element.

  Note: Clean oil is essential to the hydraulic system: impurities entering small damping holes or precision component gaps can damage components, jam oil passages, and endanger safe operation. Impurities can enter via unclean hydraulic oil, unclean filling tools, careless filling or maintenance, impurities shed from hydraulic elements, or air/water ingress.

• Replacing a free-standing hydraulic pump on a telescopic spreader

  1. Turn off the electrical supply using the main switch.
  2. Disconnect the inlet, outlet and drain hoses from the pump.
  3. Fit the new pump.
  4. Reconnect the inlet and outlet hoses.
  5. Reconnect the drain hose to the pump.
  6. Set the pump flow and pressure per the relevant drawing.

  Note: When ordering a new hydraulic pump, always state the direction of rotation as marked on the old pump housing. Every time the pump is emptied, new oil must be added until it starts to run out of the drain hose.

• Changing the oil in a mobile harbour crane's pumps coupler unit

  1. Vent the coupler through the breather fitted on its upper part.
  2. Drain the oil through the plug fitted in the lower part.
  3. Disconnect the radiator return pipe to discharge the oil from the cooling circuit.
  4. Fill through the upper plug to the maximum level shown on the dipstick.
  5. After starting the main engine, check the oil level again and top up if necessary.

  Note: Change the oil according to the time intervals shown in the maintenance table. The replacement oil must be the same as, or equivalent to, the oil already in the coupler.

Filtration & fluid

• How often must the hydraulic system fluid and filter be replaced on a terminal tractor?

  Periodicity: at least once a year, minimum

  1. Replace both the hydraulic system fluid and the filter at least once a year at the very minimum.

  Note: Never exceed this interval.

• Under what condition should hydraulic oil level be checked, and how?

  1. Check the level of the hydraulic oil with the motor switched off.
  2. Make sure the level reaches the top notch.
  3. Before topping up, make sure the area around the filler cap is clean and only use oil taken from a clean container.

  Notes:

  • Do not check or change the hydraulic oil level before it has cooled down.
  • Do not do any welding or have oxyhydrogen welding flames near the hydraulic oil tank.

• What safety precautions and checks apply to the hydraulic fluid sump?

  1. Before starting inspection, make sure no one starts up the machine, unless expressly asked to do so.
  2. Sight check: check the integrity, seal and fastness of the sump, and check connection pipes and unions.
  3. Oil level: check using the special indicator on the sump; a low level points to external leaks.
  4. Fluid drainage: drain through one of the free cocks under the sump into a pan; if the sump is emptied, carefully remove all impurities without using wool or man-made fibre cloths or tools that leave threads.
  5. Topping up the fluid: pre-filter the fluid at 10 microns and pour it into the sump through the quick coupling on the filter covers, using the same type of fluid as already in the sump.
  6. Changing the fluid: change up to the maximum level indicated on the sump, with all hydraulic cylinders in position.

  Notes:

  • Never use fluid that has deteriorated due to long or incorrect storage.
  • Never loosen or unscrew pipes or unions when the hydraulic system is under pressure.
  • Dispose of used fluid according to the regulations applicable in the country where the machine is used.

• How should the water side and oil side of a hydraulic fluid cooling circuit be cleaned?

  1. Water side: periodically inspect the water circuit to eliminate mineral deposits or impurities inside the pipes; this can be performed by removing only the bottom and swabbing the pipes.
  2. Oil side: clean by swilling with solvent to degrease aluminium parts; allow the solvent to flow against the current for about 30 minutes.
  3. Afterwards, eliminate residues by swilling with hot water.

  Note: Never loosen or unscrew pipes or unions with the hydraulic circuit under pressure.

Accumulator – Hydraulic Systems

• What is the correct sequence to replace the lift/lower accumulator damping (piston accumulator)?

  1. Put the machine in service position.
  2. Depressurize the hydraulic system.
  3. Mark up and detach the hydraulic hoses from the accumulator, plugging the connections immediately to protect the hydraulic system from impurities.
  4. Remove the accumulator attaching bolts.
  5. Remove the accumulator.
  6. Charge the new accumulator, as standard with 10 MPa preload pressure (this pressure can be lowered to achieve the desired functionality).
  7. Transfer the connection adapters to the new accumulator.
  8. Fit the new accumulator.
  9. Connect the hydraulic hoses to the accumulator according to the marking, checking that the O-rings are intact and fitted correctly.
  10. Turn on the main electric power and start the engine; run the engine at idling speed.
  11. Test the lifting and lowering a couple of times.
  12. Check that the accumulator's connections are sealed tightly.

  Notes:

  • Read the safety instructions for oil before working.
  • Handling the accumulator requires special equipment and training.

• What is the correct sequence to check the brake accumulator's pre-charge pressure without special tools?

  1. Put the machine in service position.
  2. Connect a pressure gauge (0-25 MPa) to the measuring outlet for accumulator pressure on the main valve.
  3. Turn on the main electric power and start the engine.
  4. Charge the accumulator until the accumulator charging valve changes to cooling.
  5. Turn off the engine.
  6. Lower the pressure by braking carefully several times while checking the pressure gauge; when the pressure reaches approximately 7.0 MPa it must decrease immediately to 0 MPa.
  7. Check that the accumulator's connection is sealed tightly.
  8. Once the accumulator is fully charged, turn off the engine and turn the starter key to position I.
  9. Check that at least 8 brake applications can be performed before the pressure drops to 7.0 MPa, and that the low brake pressure error code activates at 11.5 MPa.

  Notes:

  • Read the safety instructions for oil before working.
  • If the pressure decreases immediately when the engine is turned off, the accumulator has no pre-charge pressure; after checking that the accumulator drain valve is closed, this indicates inner leakage and the accumulator must be replaced.
  • If the pressure reduces slowly to below 7.0 MPa, the pre-charge pressure is too low and the accumulator must be replaced or serviced by authorised personnel.

• What is the correct sequence to replace the brake accumulator?

  1. Put the machine in service position.
  2. Depressurize the hydraulic system.
  3. Clean the accumulator and the surrounding area.
  4. Place a receptacle under the accumulator.
  5. Disconnect the hydraulic hose from the accumulator.
  6. Undo the clamp that holds the accumulator to the chassis.
  7. Transfer the connection adapter to the new accumulator, checking that the seal is intact and fitted correctly.
  8. Check that the new accumulator has the correct pre-charge pressure, according to the pressure plate.
  9. Fit the new accumulator.
  10. Connect the hose to the accumulator, checking that the O-rings are intact and fitted correctly.
  11. Turn on the main electric power and start the engine.
  12. Check that the accumulator's connection is sealed tightly.
  13. Remove the receptacle and treat the waste oil as environmentally hazardous waste.

  Note: Read the safety instructions for oil before working.

• How is the hydraulic accumulator's gas precharge pressure checked?

  1. Periodically check the gas precharge pressure, working in a fairly constant environment temperature and with the hydraulic system not under pressure.

  Notes:

  • Accumulators must only be repaired by skilled personnel.
  • Under no circumstances weld, braze, or drill the outer casing of an accumulator.
  • The compressed gas in the accumulators is dangerous due to the accumulated energy; strictly follow all safety precautions.

Cab Tipping Cylinder

• What is the correct sequence to replace the hand-controlled cab tipping pump?

  1. Put the machine in service position.
  2. Place a receptacle under the pump.
  3. Detach the hydraulic hoses from the pump.
  4. Remove the two bolts that secure the pump to the chassis.
  5. Replace the pump.
  6. Fit in reverse order.
  7. Fill up the system with hydraulic fluid.

  Note: Vent the hydraulic system by lifting and lowering the cab a few times, then check the fluid level and top up as necessary.

• What is the correct sequence to replace the electric cab tipping pump?

  1. Put the machine in service position.
  2. Place a receptacle under the pump.
  3. Detach the hydraulic hoses from the electric pump.
  4. Release the electric connections from the electric pump.
  5. Remove the bolts that secure the electric pump to the bracket.
  6. Replace the electric pump.
  7. Fit in reverse order.
  8. Fill up the system with hydraulic fluid.

  Note: Vent the hydraulic system by lifting and lowering the cab a few times, then check the fluid level and top up as necessary.

• What is the correct sequence to replace the cab tipping cylinder?

  1. Put the machine in service position.
  2. Tip the cab.
  3. Secure the cab in the tipped position by opening both cab doors and pulling a lifting strop through, fixed to a lifting device such as a travelling crane.
  4. Place a receptacle under the hydraulic cylinder.
  5. Detach the hydraulic hoses from the hydraulic cylinder.
  6. Remove the two bolts that secure the hydraulic cylinder to the chassis and cab.
  7. Replace the hydraulic cylinder.
  8. Fit in reverse order.
  9. Fill up the system with hydraulic fluid.

  Notes:

  • Protect the cab in a suitable manner to ensure it is not damaged when fixed or lifted by the lifting device.
  • Vent the hydraulic system by lifting and lowering the cab a few times, then check the fluid level and top up as necessary.

• What is the correct sequence to repair (recondition) the cab tipping cylinder?

  1. Put the machine in service position.
  2. Remove the cab tipping cylinder.
  3. Install the protection plug on the connection coupler and clean the cylinder assembly in a suitable cleaning solvent, then dry with compressed air.
  4. Connect the cylinder to a suitable cab tilt hand pump, making sure the connections match; turn the pump's selector valve to UP and operate the pump until the plunger rod is fully extended, then shift to DOWN and retract the cylinder rod approximately 10 mm.
  5. Remove the dust wiper from the cylinder top end carefully with two small screwdrivers.
  6. Use a special tool to tap the gland 5 to 10 mm back on the plunger rod.
  7. Remove the upper retaining ring from the cylinder and operate the pump to remove the plunger rod.
  8. Remove the retaining ring from the plunger rod, then remove the piston and the O-ring below it.
  9. Remove the retainer stop-ring and the gland.
  10. Check the plunger rod, the top part of the cylinder, and the inner cylinder tube for scores and damage.
  11. Slide a new wiper carefully onto the plunger rod, followed by the gland.
  12. Use a special cone to fit the retainer ring on the plunger rod.
  13. Fit a new O-ring in the groove at the plunger rod end, then slide on the piston, making sure it is fitted in the correct direction.
  14. After dismantling the plunger assembly from the cylinder, unscrew the valve (17 mm hexagon) with an extended socket wrench.
  15. Remove the pilot piston by blowing with an air nozzle in port B.
  16. Check the piston and O-ring for scratches and damage.
  17. With the cylinder tube clamped horizontally in a vice, mount the piston together with a new valve assembly and new seal rings.
  18. Tighten the valve seat to a torque of approximately 50 Nm.
  19. Use a special tool to tap the upper bearing approximately 10 mm into the cylinder and install the retaining ring, making sure it snaps into its groove.
  20. Pull back the cylinder rod with an instant jerk to place the upper bearing in the correct position.
  21. Reconnect the cylinder to the hand pump, checking the connections; turn the selector valve to DOWN/DRIVE, pump, and retract the plunger rod completely, refilling the pump reservoir with the appropriate fluid as necessary.
  22. Set the pump selector valve to UP, pump the plunger rod to the fully extended position, pressurize the system, and check for leaks.
  23. Set the pump selector valve to DOWN/DRIVE again; the pressure drops immediately but the plunger rod must remain solid, since the safety valve blocks the internal pressure — after the following pump stroke this valve opens and releases the internal pressure; if this fails, repeat the check, since the non-return valve is then suspected to leak.
  24. After completing the tests, fit the dust wiper.

  Notes:

  • Before any repair, check the cylinder assembly for excessive wear, damage, and especially scars or dents on the chromed plunger rod; if found, replace the complete cylinder instead, as repair is not justified.
  • Never use compressed air to drive out the plunger rod assembly.
  • Renew the complete cylinder if scores or scratches are found on the plunger rod or the inner cylinder tube.

Tank

• How is the hydraulic oil level checked?

  1. Check the level of the hydraulic oil with the motor switched off.
  2. Confirm the level reaches the top notch.
  3. Before topping up, make sure the area around the filler cap is clean, and only use oil taken from a clean container.

  Notes:

  • Do not check or change the hydraulic oil level before it has cooled down.
  • Do not weld or use oxy-hydrogen welding flames near the hydraulic oil tank.

• How is fluid drained from the hydraulic sump?

  1. Drain the fluid through one of the free cocks under the sump, collecting the used fluid in a pan.
  2. If the sump is emptied, carefully remove all impurities, without using wool or man-made fibre cloths or tools that leave threads.

  Notes:

  • Dispose of used fluid according to applicable regulations.
  • Never loosen or unscrew pipes or unions when the hydraulic system is under pressure.

• How is hydraulic fluid topped up in the sump?

  1. Pre-filter the fluid at 10 microns.
  2. Pour the fluid into the sump through the quick coupling on the filter covers, using a type of fluid identical to that already in the sump.

• How is the hydraulic fluid completely changed?

  1. Change the fluid up to the maximum level indicated on the sump, with all hydraulic cylinders in position.
  2. Use a fluid identical or equivalent to that already in the sump.

Hydraulic Oil

• What is the correct sequence to change the hydraulic oil?

  1. Put the machine in service position.
  2. Place a 700-litre receptacle under the hydraulic oil tank's drain plug.
  3. Remove the plug and let the oil drain into the receptacle.
  4. Fit the drain plug once the oil has drained, making sure the seal washer is installed.
  5. Handle the spent oil as environmentally hazardous waste.
  6. If the hydraulic oil filters are also due for changing, replace them before the tank is filled with oil.
  7. Fill oil through the filling holes on the filters' cover plates, so the oil being filled is itself filtered.
  8. Check the oil level in the hydraulic oil tank with the boom completely lowered and retracted; the oil level should be visible in the level glass, topping up if needed.

  Note: Always depressurize the hydraulic systems before starting to work in them; avoid skin contact with the oil, use protective gloves.

• What is the correct sequence to check the hydraulic oil level?

  The oil level is checked with the mast lowered and the attachment in the 20-foot position.

  1. Put the machine in service position.
  2. Check the oil level in the hydraulic oil tank, which should be in the centre of the sight glass, filling as required.

• What is the correct sequence to change the hydraulic oil?

  1. Put the machine in service position.
  2. Remove the filler cap and pump out the hydraulic oil into a collection container.
  3. Once most of the oil has been pumped out, place a container under the tank's drain plug and drain the last of the oil.
  4. Fit the drain plug once the oil has drained, making sure the washer seal is included.
  5. If the hydraulic oil filters are also due for changing, replace them before filling the tank with oil.
  6. Fill new hydraulic oil in the filler holes on the filters' cover plates, so the oil being filled is itself filtered, until the level is in the middle of the sight glass, with all hydraulic cylinders retracted.

  Notes:

  • Ensure cleanliness around the filter and filling point; dirt particles may cause machine damage.
  • Do not overfill, due to risk of leakage and environmental damage.

• What hydraulic-system operations are checked during the 500-hour Type A preventive maintenance service?

  There are four preventive maintenance cards (A, B, C, D) covering the machine's complete maintenance plan, on a 500-hour frequency, cycling in the order B-A-B-C-B-A-B-C-B-D before repeating. Service times assume normal operating conditions and may vary with type of use, road surface, and environment.

  1. Check the hydraulic oil level.
  2. Check for oil leaks from the hydraulic system's pipes, fittings and components.
  3. Check the operation of the hydraulic oil cooling fans.
  4. Check the hydraulic oil cooling fans' wiring.
  5. Clean the hydraulic oil radiator.
  6. Check the condition of the primary hydraulic components.
  7. Check for oil leaks from pipes, fittings and components (general).

  Note: Maintenance must be carried out only by qualified, authorised personnel, working in conditions of maximum safety.

Pumps & power

• What factors should be periodically checked when inspecting hydraulic pumps?

  1. Viscosity of the fluid used.
  2. Oil level (a low level slows down machine operating speed).
  3. Noise.
  4. Condition of filters (a blocked filter slows down oil flow and reduces pump speed).
  5. Blow-bys and oil leaks.
  6. Outlet valve adjustment.
  7. Rate of flow and pressure, using special instruments.

  Notes:

  • Only skilled personnel are allowed to use measuring instruments.
  • Never loosen or unscrew pipes and unions when the hydraulic system is under pressure.

• What precautions should be followed when replacing hydraulic motor components?

  1. Work in a clean environment.
  2. Work with solvents and blow clean air onto all parts, except the gaskets, before re-assembly.
  3. Take care not to damage the gaskets.
  4. Do not dent the worked surfaces.
  5. Make sure the components enter their housings without excessive pressure, which would indicate incorrect assembly.
  6. Whenever hand pressure is not enough, use only rubber hammers, never steel hammers.
  7. Maintain the set direction of rotation during assembly.

Accumulators & damping

• Why must a hydraulic accumulator's outer casing never be welded, brazed or drilled?

  1. The accumulators must only be repaired by skilled personnel.
  2. Under no circumstances must the outer casing be welded, brazed or drilled.

  Note: The compressed gas in the accumulators is dangerous due to the accumulated energy.

• What is the correct sequence to depressurize the hydraulic system before working on it?

  1. Put the machine in service position.
  2. Depressurize the hydraulic system by opening the accumulator drain valve on the valve block.
  3. Verify that the accumulator pressure has been released, measuring with a pressure gauge on the pressure check connection by the accumulator charging valve.

  Notes:

  • Keep the drain valve open as long as work is in progress.
  • Working with a pressurized hydraulic system endangers your life.
  • Avoid skin contact with the oil; warm oil can cause burn injuries, rashes and irritation, and may be corrosive to mucous membranes in the eyes, skin and throat.

Control Levers

• What is the correct sequence to replace a load handling control lever?

  1. Put the machine in service position.
  2. Depressurize the hydraulic system.
  3. Remove the cover from the control levers (six screws).
  4. Detach the control levers from the bracket (four screws).
  5. Cut the cable tie and fold down the gaiter to expose the control levers' connections.
  6. Lift the control levers off the bracket.
  7. Remove the hose connections.
  8. Unscrew the control levers.
  9. Replace the control lever in question, replacing the O-ring as well in case of leakage.
  10. Check that there are no leaks when the levers are refitted.
  11. Fit in reverse order.

• What checks should be performed when function-testing the electro-hydraulic control levers?

  1. Check if the dead zone is sufficient by test-running the machine on a rough surface and noting whether any hydraulic function moves; if it does, increase the dead range (for example, by 10 steps).
  2. Check the smoothness of the lift/lower movement at idle and at maximum rpm.
  3. Check the smoothness of the tilt in/out movement, in the same way as lift/lower.
  4. Check the smoothness of the side shift movement, in the same way as lift/lower.
  5. Check the smoothness of the positioning (spreading) movement, in the same way as lift/lower.
  6. Check the smoothness of the levelling movement, in the same way as lift/lower.

Tilt Cylinder

• What is the correct sequence to replace the tilt cylinder?

  1. Tilt the mast forward.
  2. Put the machine in service position.
  3. Depressurize the hydraulic system.
  4. Connect lifting equipment to the lifting lugs on the mast in a secure manner.
  5. Secure the tilt cylinder to an overhead crane.
  6. Place a container under the hose connections on the tilt cylinder to collect oil waste.
  7. Mark and undo the hydraulic connections to the tilt cylinder, plugging all connections at once to protect the hydraulic system from contamination.
  8. Release the tilt cylinder from the mast and frame by removing the screws that hold the lock plate for the cylinder shafts.
  9. Remove the cylinder shafts, using a slide hammer if necessary.
  10. Remove the tilt cylinder.
  11. Transfer the connection adapters to the new tilt cylinder.
  12. Connect the new tilt cylinder: install the cylinder shafts, checking that the bearings in the cylinder anchorages are correctly aligned before installing them; rotate the shaft to find the correct position for the lock plate; mount the lock plate and secure it with the two screws; repeat for the other cylinder.
  13. Grease the cylinder anchorages.
  14. Connect the hydraulic hoses to the tilt cylinder according to the marking, checking that the O-rings are intact and fitted correctly.
  15. Undo the lifting equipment.
  16. Turn on the main electric power and start the engine; run the engine at idling speed.
  17. Test the tilt a couple of times.
  18. Check that the tilt cylinders' connections are sealed tightly.
  19. Check the tilt function, adjusting the new tilt cylinder as necessary.

  Note: Read the safety instructions for oil before working.

• How is the tilt cylinder stroke adjusted if the mast is twisted during tilting?

  Applies if the mast becomes twisted rather than stopping solidly during tilting in or out.

  1. Tilt the mast so that the cylinders are half extended.
  2. Put the machine in service position.
  3. Undo the screws.
  4. Turn the piston rod with a hook spanner.
  5. Check that the cylinder strokes are equal in length.
  6. Check the tilt function, repeating the adjustment until the tilt function operates correctly.
  7. Install the screws.

Main Valve

• What is the correct sequence to inspect and adjust hydraulic pressures on the main valve?

  1. Warm the machine up so the hydraulic oil reaches working temperature, about 50°C.
  2. Switch off the engine.
  3. Connect a pressure gauge to the relevant measurement union on the main valve.
  4. Start the engine and check accumulator charging: allow the accumulator to charge until charging switches to cooling the brakes, read the pressure and compare it with the permissible pressure on the pressure sign, then apply the brakes repeatedly and read off the pressure at which the accumulator starts charging again (should be about 13.5 MPa), adjusting as necessary with the accumulator pressure adjustment screw.
  5. Check steering pressure: increase the engine speed to about 1100 rpm, turn the steering to full lock and continue activating the function, read the pressure and compare it with the pressure sign, then increase engine speed to about 1800 rpm and read the pressure again — the difference should not exceed ±1.0 MPa — adjusting as necessary with the steering pressure adjustment screw.
  6. Check lift and tilt pressure: increase the engine speed to about 1100 rpm, activate the tilt to its end position and continue activating the function, read the pressure and compare it with the pressure sign, then increase engine speed to about 1800 rpm and read the pressure again — the difference should not exceed ±1.0 MPa — adjusting as necessary with the lift and lower adjustment screw.
  7. Check side shift and spreading pressure: increase the engine speed to about 1100 rpm, activate side shift or spread to its end position and continue activating the function, then read the pressure (this pressure is not adjustable).
  8. Check the servo pressure to the control levers: read the pressure and compare it with the pressure sign, adjusting as necessary with the servo pressure adjustment screw.

  Notes:

  • Read the safety instructions for oil before work.
  • The hydraulic pressure must only be adjusted by authorised personnel.

• What precautions must be followed when servicing the main valves?

  1. Never use the spool ends or housings for clamping or gripping when lifting a valve block.
  2. Never subject spool ends or housings to blows or shocks, since rough treatment may deform the spool and lead to immediate seizure.
  3. Protect the valves from moisture and dirt, taking particular care to prevent dirt from entering the connection ports; protect the ports and other joint faces from scoring and bruising, and keep unconnected ports plugged.
  4. When fitting pipes and hose couplings, observe meticulous cleanliness, ensuring no swarf, flakes of paint or other impurities enter the valve, and do not overtighten the couplings.

Other Hydraulic Systems procedures

• What rules apply when installing a new flexible hydraulic hose?

  1. Avoid fitting and leaving taut flexible hoses; hoses must be fitted so they are not under tension except that of their own weight.
  2. Never fall below a minimum acceptable curving radius.
  3. If the hose makes a curve, it must be long enough to respect the straight sections.
  4. Choose the shape of the terminals to prevent further stress on the hose.
  5. Cover any structure or area the hose could come into contact with, to protect it against undesired external action.

• What is the correct sequence to replace a load control valve?

  1. Put the machine in service position.
  2. Depressurize the hydraulic system.
  3. Detach the hydraulic hose from the load control valve, plugging the connection immediately to protect the hydraulic system from impurities.
  4. Remove the connection adapter.
  5. Undo the old load control valve with a flat blade screwdriver and remove it.
  6. Fit the new load control valve (torque a 1-inch valve to 20 Nm).
  7. Fit the connection adapter.
  8. Connect the hydraulic hose to the adapter, checking that the O-rings are intact and fitted correctly.
  9. Turn on the main electric power and start the engine; run the engine at idling speed.
  10. Test the lifting and lowering a couple of times, checking the maximum lowering speed with maximum load.
  11. Check that the connections are sealed tightly.

  Note: Read the safety instructions for oil before working.

• What is the correct sequence to replace the side shift cylinder?

  1. Put the machine in service position.
  2. Secure the side shift cylinder to the fork carriage with a strap.
  3. Remove the shaft connecting the side shift cylinder to the fork by removing the screw and knocking out the shaft.
  4. Contract the side shift cylinder with the machine running.
  5. Put the machine in service position.
  6. Depressurize the hydraulic system.
  7. Place a receptacle under the hydraulic hoses attached to the side shift cylinder.
  8. Mark up and detach the hydraulic hoses from the side shift cylinder, plugging the connection immediately to protect the hydraulic system from impurities.
  9. Remove the shaft connecting the side shift cylinder to the carriage by removing the screw and pulling out the shaft.
  10. Transfer the connection adapters to the new side shift cylinder.
  11. Fit the new side shift cylinder.
  12. Fit the shafts and screws that connect the side shift cylinder to the fork carriage and forks.
  13. Connect the hydraulic hoses to the side shift cylinder according to the marking, checking that the O-rings are intact and fitted correctly.
  14. Turn on the main electric power and start the engine; run the engine at idling speed.
  15. Test the side shift and spreading a couple of times.
  16. Check that the connections are sealed tightly.

  Note: Read the safety instructions for oil before working.

• What is the correct sequence to replace the spreading flow divider?

  1. Put the machine in service position.
  2. Depressurize the hydraulic system.
  3. Place a container under the flow divider to collect oil waste.
  4. Mark up and detach the hydraulic hoses from the flow divider, plugging the connections immediately to protect the hydraulic system from impurities.
  5. Remove the two bolts that secure the flow divider to the carriage.
  6. Remove the flow divider.
  7. Transfer the connection adapters to the new flow divider.
  8. Fit the new flow divider.
  9. Connect the hydraulic hoses to the flow divider according to the marking, checking that the O-rings are intact and fitted correctly.
  10. Turn on the main electric power and start the engine; run the engine at idling speed.
  11. Test the spreading a couple of times.
  12. Check that the flow divider's connections are sealed tightly.

  Note: Read the safety instructions for oil before working.

• What is the correct sequence to replace the load holding valve?

  1. Put the machine in service position.
  2. Depressurize the hydraulic system.
  3. Mark up and detach the hydraulic hoses from the load holding valve, plugging the connections immediately to protect the hydraulic system from impurities.
  4. Remove the two bolts that secure the load holding valve to the chassis.
  5. Remove the load holding valve.
  6. Fit the new load holding valve.
  7. Turn on the main electric power and start the engine; run the engine at idling speed.
  8. Test the tilt a couple of times.
  9. Check that the load holding valve's connections are sealed tightly.

  Note: Read the safety instructions for oil before working.

• What is the correct sequence to replace the levelling cylinder?

  1. Put the machine in service position.
  2. Remove the screw that holds the rod end of the cylinder in the fork carriage.
  3. Contract the cylinder with the machine running so the rod goes into the cylinder.
  4. Put the machine in service position.
  5. Depressurize the hydraulic system.
  6. Mark and undo the hydraulic connections to the levelling cylinder, plugging all connections at once to protect the hydraulic system from contamination.
  7. Remove the split pin and the shaft that is holding the cylinder in the fork.
  8. Remove the levelling cylinder.
  9. Transfer the connection adapters to the new levelling cylinder.
  10. Connect the new levelling cylinder: install the cylinder shaft and split pin holding the cylinder to the fork, and install the screw holding the cylinder to the fork carriage.
  11. Connect the hydraulic hoses to the levelling cylinder according to the marking, checking that the O-rings are intact and fitted correctly.
  12. Turn on the main electric power and start the engine; run the engine at idling speed.
  13. Test the levelling a couple of times.
  14. Check that the levelling cylinder's connections are sealed tightly.

  Note: Read the safety instructions for oil before working.

• What is the correct sequence to calibrate the automatic clamping function?

  1. Select calibration of the automatic clamping function from the setup menu.
  2. Close the automatic clamping unit completely, then open it slightly so the clamp is almost closed but under no pressure.
  3. Confirm to start the automatic calibration; the current on the cartridge is slowly increased while current and pressure are recorded.
  4. Wait for calibration to complete; if successful, the values are stored in the ECU memory, otherwise the calibration is reported as failed and no values are saved.

  Notes:

  • The clamping pressure rises to 160 bar during calibration, which can damage a roll; use an already damaged roll for calibration.
  • Calibration fails and the values are not saved if the pressure was too high when calibration started (above 40 bar) or if the pressure did not reach 160 bar during calibration.

• What is the correct sequence to replace the hydraulic tank heater?

  1. Put the machine in service position.
  2. Depressurize the hydraulic system.
  3. Drain the machine of hydraulic oil using a pumping device.
  4. Remove the two screws that hold the plastic cover.
  5. Unplug the electric cables from the connections.
  6. Remove the lock nut which holds the wiring harness in the heater.
  7. Remove the heater from the machine.
  8. Replace the heater.
  9. Fit in reverse order.

  Notes:

  • Read the safety instructions for oil before working.
  • The tank heater is connected to high voltage (110-400V); connection and reconnection may only be performed by personnel authorised to work with high voltage.

• What is the correct sequence to replace the hydraulic oil temperature sensor?

  1. Put the machine in service position.
  2. Depressurize the hydraulic system.
  3. Detach the electrical connectors from the sensor.
  4. Replace the sensor.
  5. Fit in reverse order.

• What precautions should be observed when replacing a hydraulic motor?

  1. Work in a clean environment.
  2. Work with solvents and blow clean air onto all parts (except the gaskets) before re-assembly.
  3. Take care not to damage the gaskets.
  4. Do not dent the worked surfaces.
  5. Make sure the components enter their respective housings without undergoing excessive pressure, which would indicate an incorrect assembly position.
  6. When hand pressure is not enough, use only rubber hammers, never steel hammers.
  7. Maintain the set direction of rotation during assembly.

• How is the hydraulic fluid cooling circuit (heat exchanger) cleaned?

  1. On the water side, periodically remove the bottom of the exchanger and swab the pipes to eliminate mineral deposits or other impurities.
  2. On the oil side, clean by swilling with a solvent (perchlorethylene) to degrease the aluminium parts, letting the solvent flow against the current for about 30 minutes, then eliminate residues by swilling with hot water.

• What is the correct sequence to troubleshoot a suspected hydraulic hose fault?

  1. Depressurize the hydraulic and brake systems.
  2. Study the relevant hydraulic diagram, checking between which components the suspected hose is connected and where it is spliced.
  3. Locate the hose on the machine, starting at one component and following the hose to the next.
  4. Inspect the entire hose and splicing points for chafing damage, pinching damage, and leaks, changing any damaged hoses.

  Notes:

  • Always depressurize the hydraulic and brake systems before starting work on them, due to the risk of personal injury from oil under high pressure.
  • When removing a hydraulic hose, always change the O-ring on hoses that have one (ORFS).

• What is the correct sequence to change the load handling servo filter?

  1. Put the machine in service position.
  2. Depressurize the hydraulic systems.
  3. Turn the start key to position 0 and turn off the main electric power.
  4. Clean the outside of the filter housing and filter holder.
  5. Remove the filter holder and remove the cartridge downward.
  6. Clean the inside of the filter holder.
  7. Place the new cartridge in the filter holder.
  8. Check that the O-ring on the filter holder is intact and in place.
  9. Fit the filter and filter holder.
  10. Check the hydraulic oil level with the lift cylinders completely down and the extension cylinder completely in; the level should be at the top of the level glass, topping up as needed.

  Notes:

  • Always depressurize the hydraulic systems before working on them; avoid skin contact with the oil, use protective gloves.
  • The hydraulic oil level is checked with the boom completely lowered and retracted.

• What is the correct sequence to check the servo pressure at the pressure reducer?

  1. Operate and warm up the machine so the hydraulic oil reaches operating temperature, at least 50°C.
  2. Put the machine in service position.
  3. Depressurize the hydraulic systems.
  4. Turn the start key to position 0.
  5. Connect a pressure gauge (0-25 MPa) to the test outlet on the pressure reducer.
  6. Start the engine and check the servo pressure, comparing it with the pressure plate; turn the steering wheel or activate a load handling function to activate the hydraulic oil pumps, since the servo pressure is higher than their stand-by pressure.
  7. Depressurize the hydraulic and brake systems.
  8. Remove the pressure gauge and fit the protective cap on the pressure check connection.

  Note: Always depressurize the hydraulic systems before working on them; avoid skin contact with the oil, use protective gloves.

• What is the correct sequence to change the hydraulic oil tank's breather filter?

  1. Turn off the engine and the main electrical power.
  2. Clean the area around the filter housing.
  3. Remove the filter housing by pressing down and turning approximately 1/8 turn clockwise.
  4. Change the filter cartridge, handling it as environmentally hazardous waste.
  5. Fit the filter housing by pressing down and turning approximately 1/8 turn counter-clockwise.
  6. Reset the filter indicator by pressing down the button in the middle of the glass centered on the filter cartridge.

  Confirmed across independent manufacturers’ manuals.

• What is the correct sequence to check and top up the hydraulic fluid level?

  If the machine has an oil-cooled wet disc brake system, any hydraulic oil used for topping up should contain a friction-modifying additive necessary for good brake system performance; the additive is not consumed during normal operation and must only be added at oil change and refill.

  1. Check the fluid level on the fluid sight-glass, with all hydraulic pistons in the bottom positions.
  2. Top up the hydraulic fluid as necessary, using the specified oil grade.

  Notes:

  • Hydraulic fluid is chemically aggressive; avoid extended contact with the skin.
  • In systems with a separate tank for the brake system, the hydraulic fluid for the brake system must never contain any additives.

• What is the correct sequence to check the accumulators' pre-charging pressure?

  Periodicity: At least once every year.

  1. Always check that the engine shut-off controls function correctly.
  2. Empty the accumulators into the tank by opening the accumulator evacuating valve.
  3. Remove three of the accumulators from the connector and plug the connector holes.
  4. Connect a 0-250 bar pressure gauge to the test outlet on the accumulator charging valve.
  5. Start the engine and allow the first accumulator to build up pressure.
  6. Switch off the engine and reduce the pressure by pumping the foot brake repeatedly; the pressure should fall slowly until approximately 5 bar below the recommended pre-charging (gas) pressure, then fall to 0 immediately, and any earlier immediate drop indicates internal leakage requiring replacement.
  7. Open the accumulator evacuating valve and empty the accumulator into the tank.
  8. Repeat the check for the other three accumulators.

  Notes:

  • Always empty the accumulators before working on the system, using the accumulator evacuating valve adjacent to the accumulator connection point, and open the reserve servo pressure valve too.
  • Immediately shut down the engine if the charging pressure exceeds the levels stated on the hydraulic system information plate.

• What is the correct sequence to adjust the wet disc brake (WDB) system?

  The engine and hydraulic system should be at normal operating temperature before adjustments are carried out. Always check that the engine stopping device is working.

  1. Check the pre-charging pressure of the accumulators.
  2. Check the accumulator charging pressure with the engine stopped: connect a pressure gauge to the measurement tapping on the accumulator charging valve, discharge the accumulator with the evacuating valve, close the evacuating valve, start the engine, let the accumulator charge, and read the charging pressure, adjusting the accumulator charging valve and repeating as necessary.
  3. Bleed the brake circuit: open the bleed nipple on the inside of each drive axle hub, depress the brake pedal, let the oil flow out until free from air bubbles, then shut off the nipple while the pedal is still depressed; repeat for the other hub.
  4. Check the pressure from the brake pedal: connect a pressure gauge to the measurement tapping on the brake pedal valve below the operator's cab, depress the pedal fully, and read the pressure against the hydraulic system plate, leaving the gauge in position.
  5. Stop the engine and check for leakage at the pedal: depress the pedal and read the pressure, which must not drop for 15 seconds; release the pedal and confirm the pressure drops to 0, otherwise the brake valve is leaking.
  6. Use the accumulator evacuating valve to release the pressure from the accumulator.
  7. Start the engine and run it until full pressure is achieved.
  8. Stop the engine and check that the brakes can be applied 6-8 times before the pressure drops to 70 bar, and that the low brake pressure warning lamp lights up at 115 bar.

• What is the correct sequence to depressurise the hydraulic and brake systems?

  1. Put the machine in service position.
  2. Depressurise the working hydraulic system: turn on the system voltage, turn the start key to position I, and repeatedly activate the load handling functions.
  3. Turn the start key to position 0 and turn off the system voltage.
  4. Depressurise the brake system by opening the drain valve on the accumulator charging valve.
  5. Depressurise the attachment by opening the attachment relief valve.

  Notes:

  • Keep the accumulator drain valve open as long as work is in progress; after finishing, close the drain valve and tighten the lock ring.
  • Hydraulic oil may be directed the wrong way through the fine filter if the attachment relief valve is not closed before the engine is started; check that it is closed.

Looking for general maintenance tips and checklists? See Hydraulic Systems.