Cooling Circuit Procedures

This page lists 20 maintenance procedures for cooling circuit (engine & cooling), drawn from HIT Srl's internal procedure library extracted from manufacturer service manuals.

HIT Srl supplies engine, fuel-system and cooling-circuit spare parts for this class of machine.

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

Cooling Circuit

• How often should engine coolant be tested and replaced on a terminal tractor?

  Periodicity: test every 250 hours, replace every 2000 hours minimum

  1. Test coolant every 250 hours.
  2. Replace coolant every 2000 hours at the very minimum.

  Notes:

  • Exceeding these intervals may damage the cooling system or lead to injury.
  • Never attempt to open the radiator cap when the engine is hot; always allow the engine and coolant to cool completely first, or hot coolant may spray out and cause severe burns or blindness.

• Under what condition should the engine coolant level be checked?

  1. Sight-check the level of the coolant in the tank.
  2. Perform the inspection when the motor is cold, and make sure the level is between minimum and maximum.

  Note: Do not remove the radiator cap or filler cap if the engine is hot; the coolant is under pressure and can escape with explosive force, causing burns.

• What is the correct sequence to change the engine coolant on a container stacker?

  1. Unscrew the drain cap under the radiator.
  2. Pour fresh water into the radiator to swill the circuit.
  3. When the water comes out clean, close the drain cap.
  4. Fill up with new coolant, using the mix indicated in the engine manual.

  Notes:

  • Disengage the battery disconnector before performing any maintenance jobs on the engine.
  • The liquid inside the radiator could be very hot; to check the coolant, make sure the engine is switched off and the radiator is cool.

• How and how often should engine coolant level be checked?

  Periodicity: every day

  1. Check the coolant level cold, with the engine off; it must be between the MIN and MAX marks on the expansion tank's level indicator.
  2. The liquid should reach the MAX mark; never let it fall below MIN.

  Note: Do not open the tank cap, breather caps, or the circuit tap when the engine is hot; the cooling system is under pressure and splashes of boiling liquid can cause serious burns.

• What is the correct sequence to replace the engine coolant filter?

  The coolant filter provides anti-rust protection and must not be replaced together with the coolant itself, to avoid excess corrosion protection causing clogging.

  1. Close tap "1" on the circuit, located on the filter support.
  2. Remove the filter with a suitable tool.
  3. Carefully clean the cartridge seat on the support.
  4. Lubricate the new filter's gasket with engine oil.
  5. Screw the new filter on by hand until the gasket contacts the sealing surface.
  6. Tighten a further 1/2 to 3/4 turn, no more.
  7. Reopen tap "1".

  Note: Do not replace the filter when the engine is hot; the cooling system is under pressure and splashes of boiling liquid can cause serious burns.

• What is the correct sequence to replace the engine coolant?

  1. Position the vehicle on level, compact ground.
  2. Remove the filler cap "T" on the coolant tank.
  3. Drain the system's liquid into a suitable container by opening tap "R" on the iron pipe between the radiator and the heat exchanger, and also remove cap "B" from the heat exchanger (both are at the lowest point of the cooling circuit).
  4. Wait for the coolant to drain completely, then close tap "R" and refit cap "B" on the heat exchanger.
  5. Introduce into the circuit water mixed with radiator descaler at the percentages prescribed on the product container.
  6. Run the engine at medium speed for 15 minutes, then, without stopping the engine, drain the solution as described above while simultaneously feeding running water through the expansion tank for at least 40 minutes.
  7. Drain all the water from the circuit as described above, then close tap "R" and refit cap "B".
  8. Slowly pour the new coolant into the tank until the system is completely full.
  9. Start the engine and let it run until air stops escaping from the coolant tank.
  10. Screw the tank cap "T" back on.
  11. Run the engine for a few minutes, then let it cool and top up the level.

  Notes:

  • Do not open the tank cap, breather caps or circuit tap when the engine is hot.
  • Do not pour cold coolant into a hot engine, as this could damage the block and cylinder head.

• How often should the radiator core be checked and cleaned?

  Periodicity: every week

  1. Check the cleanliness of the radiator core; if obstructed by dirt, mud or leaves, clean it immediately using compressed air or steam.

  Note: Using compressed air or steam for cleaning requires adequate hand, face and eye protection.

• What condition applies to mixing antifreeze with engine coolant?

  1. Mix the glycol with clean water meeting ASTM D4985 in a separate container before filling the cooling system.
  2. Never replace the coolant with plain water, even in summer; maintain the 50% water / 50% antifreeze proportion.
  3. Check the antifreeze percentage using the specific hydrometer through the filler cap.

  Notes:

  • Glycol is harmful to health if ingested.
  • Do not use alcohol in the cooling system.
  • Never mix antifreeze (glycol) with corrosion-inhibiting agents; the two substances mixed together form foam and drastically reduce the coolant's effectiveness.

• How is engine coolant level checked and topped up?

  1. Put the machine in service position.
  2. When needed, top up with ready-mixed recommended coolant.

  Notes:

  • The coolant level should be between the MIN and MAX markings on the expansion tank.
  • If the coolant level becomes too low, an error code is shown in the control system's display; a low coolant level may cause engine damage or cause the engine to stop.
  • The cooling system is pressurised; open the filler cap very slowly when the engine is warm, and wait until the coolant has cooled down before topping up.
  • Different types of coolant must not be mixed; when changing or topping up, only use coolant of the same type used before.

• What is the correct sequence to replace the radiator package?

  1. Put the machine in service position.
  2. Remove the engine compartment hood.
  3. Drain the coolant and transmission oil out of the system via the coolant drain cock.
  4. Undo the hoses for the intercooler, engine and transmission cooling, and for the expansion tank, from the radiator (the expansion tank hoses only need to be undone if its bracket is fixed directly to the engine on the specific engine variant fitted; on other variants the expansion tank is fixed to the radiator package and is removed together with it).
  5. Remove the screws that fix the radiator package to the chassis.
  6. Lift the radiator package gently out of the chassis.
  7. Install in reverse order.
  8. Check and top up fluids as necessary.

  Note: Read the safety instructions for oil and for the cooling system before working.

• What is the correct sequence to replace the intercooler?

  1. Put the machine in service position.
  2. Remove the radiator package.
  3. Remove the screws that fix the fan housing.
  4. Remove the radiator section by undoing its screws.
  5. Install in reverse order.
  6. Check and top up fluids as necessary.

• What is the correct sequence to change and clean the engine cooling system, using the water-flush method?

  Documented for one engine alternative in the manual; a different engine alternative instead uses a chemical (sodium carbonate) cleaning method, described separately.

  1. Put the machine in service position; stop the engine, let it cool, and slowly remove the filler cap from the expansion tank.
  2. Open all drain points and drain the coolant from the radiator and engine block via a drain hose; the drainage nipples are on the radiator and on the side of the engine block.
  3. Check that all coolant has drained; leave the drain cocks/plugs open and set the heating control to full heat during cleaning.
  4. Check the condition of the hoses, clamps and radiator sealing, replacing or cleaning as needed.
  5. Insert a hose in the expansion tank filler hole and flush with clean water until the draining water runs clear.
  6. Once the system is free of impurities, close the drain cocks and plugs.
  7. Fill with clean water to a level between the MIN and MAX marks, and fit the filler cap.
  8. Switch off the system voltage and start the engine once the system is fully bled and filled; let it idle until the temperature reaches 49-66°C, opening all heater controls to bleed the heater unit.
  9. Stop the engine, let it cool, and repeat the drain-and-flush cycle (remove filler cap, open drain points, drain, flush with clean water) until the draining water runs clear.
  10. Close the drain cocks and plugs once the system is free of impurities.
  11. Fill the coolant to a level between MIN and MAX; do not fit the filler cap yet, as the engine must not be started before the system is bled and completely filled.
  12. Start the engine and let it idle until the system is fully bled and filled; increase to raised idling speed with all heat controls open to ventilate the heater unit, running for a minute to expel trapped air, then stop the engine.
  13. Check the coolant level and top up if required.
  14. Clean the pressure cap and check its gasket, replacing the cap if the gasket is damaged; if intact, pressurise the cap with a suitable pump and confirm it holds the pressure stamped on the cap, replacing it if it does not.
  15. Start the engine, check the cooling system's seal integrity, and confirm the engine reaches the correct operating temperature.

  Notes:

  • The cooling system is pressurised; open the filler cap very slowly when the engine is warm and wait for the coolant to cool before topping up.
  • Glycol and anti-corrosion agents are hazardous to health; avoid skin contact and wear protective glasses and gloves.
  • On machines with a combined heating/cooling package, disconnect the electrical connection to the AC compressor before cleaning the radiator with water or a cleaning agent without anti-freeze properties, to avoid a freezing risk.
  • Air pockets in the cooling system can damage the engine.
  • Different types of coolant must not be mixed.

• What is the correct sequence to change and clean the engine cooling system, using the chemical (sodium carbonate) cleaning method?

  Documented for one specific engine alternative in the manual; a different engine alternative instead uses a water-flush cleaning method, described separately.

  1. Remove the filler cap from the expansion tank.
  2. Open all drain points and drain the coolant from the radiator and engine block; a drain nipple is located under the radiator and a drain plug under the coolant intake on the engine block.
  3. Check that all coolant has drained; leave any additional drain valves or plugs open and set heat control to full heat during cleaning.
  4. Check the condition of the hoses, clamps and radiator sealing, replacing or cleaning as needed.
  5. Fill the system with a mixture of sodium carbonate and water (0.5 kg of sodium carbonate per 23 litres of water), without fitting the pressure cap.
  6. Start and run the engine for 5 minutes with the coolant temperature over 80°C, then turn it off and empty the cooling system.
  7. Fill the cooling system with clean water, ensuring it is properly bled, without fitting the pressure cap.
  8. Start and run the engine for 5 minutes with the coolant temperature over 80°C again.

  Notes:

  • The system must be filled well to prevent air pockets; during filling, air must be vented from the cooling channels, waiting 2-3 minutes to allow the system to bleed before filling.
  • The cooling system is pressurised; open the filler cap very slowly when the engine is warm.
  • Glycol and anti-corrosion agents are hazardous to health; avoid skin contact.

• What is the correct sequence to replace the low coolant level switch?

  1. Put the machine in service position.
  2. Open the engine hoods.
  3. Release the expansion tank from its bracket.
  4. Unplug the connector for the switch.
  5. Withdraw the switch from the expansion tank.
  6. Install in reverse order.

• How is the engine coolant level checked?

  1. Sight check the level of the coolant in the tank.
  2. Perform the inspection when the engine is cold and make sure the level is between the minimum and maximum marks.

  Note: Do not remove the radiator cap or filler cap if the engine is hot; the coolant is under pressure and can escape with explosive force. Remove the cap only when the engine is cool.

• What is the correct sequence to change the radiator coolant?

  1. Unscrew the drain cap under the radiator.
  2. Pour fresh water into the radiator to flush the circuit.
  3. When the water runs out clean, close the drain cap.
  4. Fill up with new coolant, using the mix indicated in the engine manual.

  Notes:

  • Disengage the battery disconnector before performing any maintenance on the engine.
  • The liquid inside the radiator can be very hot after the engine stops; check the coolant only when the engine is switched off and the radiator is cool.
  • Dispose of the coolant in accordance with anti-pollution regulations.

• What is the correct sequence to change the coolant filter?

  Applies to both available engine alternatives, which use the same sequence.

  1. Put the machine in service position.
  2. Close the shut-off valve on the filter holder.
  3. Clean the area around the coolant filter.
  4. Place a receptacle under the coolant filter.
  5. Remove the coolant filter with the filter tool.
  6. Lubricate the O-ring on the new filter cartridge with engine oil.
  7. Fit the new filter, tightening to contact and then another half to three-quarter turn.
  8. Open the shut-off valve on the filter holder.
  9. Turn on the main electrical power and start the engine.
  10. Check that the coolant filter seals tight.
  11. Remove the receptacle, handling the coolant as environmentally hazardous waste.
  12. Check the coolant level in the expansion tank, topping up if needed.

  Notes:

  • Close the shut-off valve before loosening the filter, or coolant may run out causing environmental damage.
  • Remember to reopen the shut-off valve after changing, otherwise the coolant will not pass through the filter and will not be cleaned.

• How is the cooling fan belt tension checked?

  1. Place the cab in the front position.
  2. Remove the cover plates over the engine and radiator.
  3. Wash the engine compartment.
  4. Put the machine in service position.
  5. Check the belt tension and adjust if needed.

• How is the engine coolant level checked and topped up?

  1. Put the machine in service position.
  2. If needed, top up with water (in winter, with at least 40% glycol); if glycol is not used, an anti-corrosion agent must be added instead, but only when the outdoor temperature is always above 0°C, since it contains no anti-freeze.

  Notes:

  • A low coolant level may cause engine damage or cause the engine to stop.
  • The cooling system is pressurized; steam or hot fluid may jet out. Open the filler cap very carefully when the engine is warm, and wait until the coolant has cooled before topping up.

• What cooling-circuit 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. Change the water filter.
  2. Check the coolant level.
  3. Check the tension and wear of the cooling belts.
  4. Clean the radiator (external).

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

Looking for general maintenance tips and checklists? See Engine & Cooling.