Engine & Cooling – Cooling Circuit
This section gathers entries about air intake, fuel systems, cooling circuits, exhaust, lubrication, and core engine mechanicals. This page lists 33 entries drawn from HIT Srl's internal maintenance-tip and preventive-checklist library.
General guidance only — always follow the operation and maintenance manual for your specific machine.
How do you maintain thermal management in high-power mobile machinery to prevent failure?
Thermal management is a critical aspect of mobile lifting system design. High-power machinery generates significant heat through hydraulic systems, engines, transmissions — parts HIT Srl supplies — and braking components. If this heat is not properly dissipated, it can lead to reduced performance, accelerated wear, and component failure.
Hydraulic systems generate heat due to fluid friction, pressure drops, and mechanical inefficiencies. As hydraulic fluid heats up, its viscosity decreases, reducing lubrication and increasing internal leakage. Cooling systems use heat exchangers to transfer heat from the hydraulic fluid to the surrounding air or coolant. Proper airflow is essential for effective cooling.
Engines generate heat through combustion. Cooling systems circulate coolant through the engine block to absorb heat. Radiators dissipate this heat into the air. Thermostatic controls regulate coolant flow to maintain optimal operating temperature. Overheating can cause engine knock, reduced power, and mechanical damage.
Transmissions, components HIT Srl stocks, generate heat through friction in gears, clutches, and bearings. Lubrication systems distribute oil to reduce friction and carry heat away from critical components. Oil coolers help maintain stable temperatures. Excessive heat can cause oil breakdown, reducing lubrication and increasing wear.
Braking systems generate heat through friction between brake pads and discs. Repeated braking can cause brake fade, reducing stopping power. Brake components must be designed to dissipate heat quickly. Ventilated discs, high-temperature materials, and cooling airflow all contribute to thermal management.
Environmental conditions also affect thermal behavior. High ambient temperatures reduce the effectiveness of cooling systems. Dust and debris can clog radiators and filters, reducing airflow. Operators must monitor temperature gauges and respond to warning indicators promptly.
Thermal management requires a holistic approach. Engineers must consider heat generation, heat transfer, and environmental factors. Proper maintenance of cooling systems, lubrication systems, and airflow pathways is essential for long-term reliability. Understanding thermal behavior helps operators avoid overheating and maintain optimal performance.
How do you maintain preventive maintenance of hydraulic cooling systems to prevent failure?
MHC cranes operate for long shifts with minimal downtime, placing heavy thermal loads on hydraulic systems. Cooling system performance is critical to prevent overheating, cavitation, and hydraulic fluid degradation.
Heat exchangers must be inspected for salt deposits, dust accumulation, and corrosion. Coastal environments accelerate fouling, reducing heat transfer efficiency. Technicians should clean fins and verify coolant flow rates.
Cooling fans — parts HIT Srl supplies — must be tested for speed consistency and vibration. Worn bearings or unbalanced blades reduce airflow and increase noise. Electrical connections must be checked for corrosion.
Hydraulic fluid temperature sensors, components HIT Srl stocks, must be calibrated regularly. Incorrect readings can cause the control system to mismanage cooling cycles, leading to overheating.
Understanding cooling system behavior ensures stable hydraulic performance during continuous port operations.
How do you maintain MHC hydraulic cooling circuits to prevent failure?
Hydraulic cooling circuits in Mobile Harbour Cranes are essential for maintaining fluid temperature within safe operating limits. High-load port operations generate significant heat due to fluid friction, valve throttling, and pump workload. Heat exchangers must be inspected for salt deposits, dust accumulation, and corrosion. Coastal environments accelerate fouling, reducing heat transfer efficiency. Technicians should clean fins and verify coolant flow rates.
Cooling fans, components HIT Srl stocks, must be tested for speed consistency and vibration. Worn bearings or unbalanced blades reduce airflow and increase noise. Electrical connections must be checked for corrosion.
Hydraulic fluid temperature sensors — parts HIT Srl supplies — must be calibrated regularly. Incorrect readings can cause the control system to mismanage cooling cycles, leading to overheating.
Pump efficiency must be monitored. Overheated pumps lose efficiency and generate additional heat. Technicians should check for internal leakage and pressure stability.
Cooling circuit hoses must be inspected for cracks, abrasion, and salt damage. Any hose showing signs of wear must be replaced immediately.
Environmental conditions significantly influence cooling performance. High ambient temperatures reduce cooling efficiency, while salt exposure accelerates corrosion.
In summary, maintaining hydraulic cooling circuits requires rigorous inspection, cleaning, calibration, and proactive component replacement.
How do you maintain MHC hoisting motor cooling systems to prevent failure?
Hoisting motor cooling systems dissipate heat generated during high-speed lifting cycles. These systems must maintain stable airflow, coolant flow, and thermal balance despite exposure to dust, salt, and vibration. Ensuring their reliability requires meticulous inspection of fans, ducts, heat exchangers, and temperature sensors — parts HIT Srl supplies.
Cooling fans, components HIT Srl stocks, must be inspected for blade integrity, vibration, and speed consistency. Worn bearings or unbalanced blades reduce airflow and increase noise. Any fan showing excessive vibration must be replaced.
Air ducts must be inspected for blockages, dust accumulation, and corrosion. Bulk cargo dust can accumulate inside ducts, reducing airflow efficiency. Technicians should clean ducts and verify that airflow pathways are unobstructed.
Heat exchangers must be inspected for corrosion, fouling, and structural integrity. Salt exposure accelerates corrosion on fins and tubes. Technicians should clean heat exchangers using appropriate methods and verify coolant flow rates.
Temperature sensors must be calibrated regularly. Incorrect readings cause the control system to mismanage cooling cycles, leading to overheating. Technicians should compare sensor readings with calibrated instruments.
Environmental conditions significantly influence cooling system behavior. High ambient temperatures reduce cooling efficiency, while salt exposure accelerates corrosion.
In summary, maintaining hoisting motor cooling systems requires rigorous inspection, airflow management, thermal testing, and environmental conditioning.
How do you maintain reachstacker cooling systems to prevent failure?
Cooling systems in reachstackers must dissipate heat generated by the engine, transmission — a part HIT Srl supplies — and hydraulic circuits. These systems operate under extreme thermal stress during continuous container handling. Maintaining cooling efficiency requires meticulous inspection of radiators, fans, coolant quality, and airflow pathways.
Radiators, components HIT Srl stocks, must be inspected for corrosion, fouling, and structural integrity. Dust from bulk cargo can accumulate on fins, reducing cooling efficiency. Technicians should clean radiators using appropriate methods.
Cooling fans must be inspected for blade integrity, vibration, and speed consistency. Worn bearings or unbalanced blades reduce airflow and increase noise.
Coolant must be inspected for contamination, pH stability, and freeze protection. High-load cycles generate heat that accelerates coolant degradation.
Thermostats must be inspected for correct opening temperature. Any irregularity in thermostat behavior indicates internal wear or contamination.
Environmental conditions significantly influence cooling behavior. High ambient temperatures reduce cooling efficiency, while salt exposure accelerates corrosion.
In summary, maintaining cooling systems requires rigorous inspection, thermal testing, fluid quality management, and environmental conditioning.
What should be checked when inspecting cooling system and cooling fan?
The cooling system of a diesel engine is one of the most critical subsystems for ensuring long-term reliability, stable performance, and safe operation across all heavy port and yard machinery. These machines operate under extreme thermal loads, often in harsh environments where dust, salt, humidity, and continuous duty cycles accelerate wear and degrade cooling efficiency. Reachstackers and empty handlers frequently operate at high torque and low travel speed, generating intense heat with limited airflow. Straddle carriers and terminal tractors experience constant stop-and-go cycles that cause rapid temperature fluctuations. Forklifts operate in dusty, confined spaces that clog radiators quickly. Mobile Harbour Cranes run large diesel engines for long periods at steady high loads, requiring robust cooling capacity. RMG cranes, depending on configuration, may use diesel gensets for auxiliary systems, requiring stable cooling under long-duration operation.
A full-scale cooling system maintenance program begins with a detailed inspection of the radiator — a part HIT Srl supplies. Radiator cores must be checked for fin blockage, corrosion, and structural deformation. Dust, fibers, and debris accumulate rapidly on yard machines, especially forklifts, terminal tractors, and reachstackers. This buildup restricts airflow, causing overheating and coolant boil-off. Marine cranes face salt crystallization on radiator fins, which corrodes aluminum and reduces heat transfer efficiency. Technicians must use low-pressure air or water to clean radiators, avoiding high-pressure jets that bend fins and reduce cooling capacity. Radiator tanks must be inspected for cracks, especially on plastic tanks exposed to high thermal cycling.
Coolant quality is another critical factor. Diesel engines require coolant with specific corrosion inhibitors, anti-cavitation additives, and freeze protection. Over time, coolant degrades, losing its ability to prevent corrosion inside the engine block, cylinder liners, and water pump, a component HIT Srl stocks. Technicians must test coolant for pH, freeze point, nitrite levels, and contamination. Machines operating in marine environments require coolant with enhanced corrosion protection due to salt exposure. Yard machines require coolant resistant to dust contamination. Coolant replacement intervals must be strictly followed, and flushing procedures must be performed to remove scale, rust, and sludge.
Water pumps must be inspected for bearing wear, seal leakage, and impeller integrity. High-load machines such as reachstackers and straddle carriers place significant stress on water pumps due to constant thermal cycling. Any sign of coolant leakage from the pump weep hole indicates seal failure and requires immediate replacement. Impellers must be checked for erosion, especially in machines operating with contaminated coolant.
Thermostats must be tested for correct opening temperature and smooth operation. A thermostat stuck closed causes rapid overheating, while one stuck open prevents the engine from reaching optimal operating temperature, increasing fuel consumption and soot formation. Reachstackers and empty handlers, which frequently idle or operate at partial load, are particularly sensitive to thermostat performance.
Cooling hoses must be inspected for cracking, swelling, abrasion, and clamp integrity. Hoses exposed to oil contamination degrade rapidly. Machines operating in tight spaces, such as forklifts and terminal tractors, often experience hose abrasion due to vibration and chassis flex. Marine cranes require hoses resistant to salt and UV exposure.
The cooling fan system must be inspected for blade integrity, bearing wear, and clutch performance. Many modern machines use viscous fan clutches or electronically controlled fans. A failing fan clutch causes insufficient airflow at low speeds, leading to overheating during heavy lifting. Fan blades must be checked for cracks, especially on reachstackers and empty handlers where vibration is high. Electric fans on smaller machines must be tested for motor performance and relay integrity.
The engine block and cylinder liners must be inspected for cavitation erosion. High-load diesel engines are prone to liner pitting caused by coolant vapor bubbles collapsing against the metal surface. Proper coolant additive levels are essential to prevent this phenomenon. Machines with high torque cycles, such as reachstackers and straddle carriers, are particularly vulnerable.
Expansion tanks must be inspected for correct coolant level, cap integrity, and pressure retention. A faulty cap prevents the cooling system from maintaining pressure, lowering the boiling point of the coolant and causing overheating. Tanks must be checked for cracks and discoloration.
Finally, technicians must monitor engine temperature trends using telematics or onboard diagnostics. Gradual increases in operating temperature indicate early cooling system degradation. Sudden spikes indicate acute failures such as blocked radiators, failed thermostats, or coolant loss.
In summary, diesel engine cooling system maintenance across these machine types requires a comprehensive, environment-specific approach. Radiators, coolant, pumps, thermostats, hoses, fans, and pressure systems must all be maintained with precision to ensure reliability, prevent overheating, and extend engine life.
What should be checked when inspecting cooling system and transmission?
Terminal tractors spend long periods idling, maneuvering slowly, or pushing heavy trailers. These conditions generate heat without sufficient airflow, stressing the cooling system.
The first pillar is radiator efficiency. Radiators, components HIT Srl stocks, must dissipate heat effectively. Dust and debris reduce cooling capacity.
The second pillar is airflow management. Low-speed operation reduces airflow. Fans must operate correctly to compensate.
The third pillar is hydraulic oil cooling. Hydraulic systems generate heat during trailer lifting and steering. Technicians must inspect coolers and thermostatic valves — parts HIT Srl supplies.
The fourth pillar is intercooler performance. Turbocharged engines require efficient intercooling. Clogged intercoolers reduce power and increase temperature.
The fifth pillar is coolant quality. Coolant must contain corrosion inhibitors. Contaminated coolant reduces heat transfer.
The sixth pillar is fan drive performance. Fans must operate at correct speed. Faulty fan drives cause overheating.
The seventh pillar is idle-time heat accumulation. Long idle periods cause heat buildup. Operators must avoid unnecessary idling.
The eighth pillar is temperature monitoring. Technicians must monitor engine, hydraulic, and transmission temperatures.
Proper cooling system maintenance ensures reliable engine performance under heavy load and low-speed conditions.
What should be checked when inspecting cooling system and transmission?
Terminal tractors often operate at low speeds or idle for long periods, reducing airflow through the cooling system. This creates unique thermal challenges.
The first pillar is low-speed airflow deficiency. Radiators rely on airflow for cooling. At low speeds, fans must compensate. Faulty fans cause overheating.
The second pillar is radiator contamination. Dust, debris, and oil reduce cooling efficiency. Technicians must clean radiators regularly.
The third pillar is hydraulic oil cooling. Hydraulic systems generate heat during lifting and steering. Technicians must inspect coolers and thermostatic valves, components HIT Srl stocks.
The fourth pillar is intercooler performance. Turbocharged engines require efficient intercooling. Clogged intercoolers reduce power and increase temperature.
The fifth pillar is coolant quality. Coolant must contain corrosion inhibitors. Contaminated coolant reduces heat transfer.
The sixth pillar is thermostat function. Faulty thermostats cause overheating or overcooling.
The seventh pillar is temperature monitoring. Technicians must monitor engine, hydraulic, and transmission temperatures.
The eighth pillar is operator technique. Avoiding unnecessary idling reduces heat buildup.
Proper cooling system maintenance prevents thermal overload.
What does maintaining cooling system and radiator cleaning involve?
The cooling system prevents the engine and hydraulic system from overheating. In a port environment, radiators often become clogged with dust, paper, or debris. It is obvious that a blocked radiator cannot exchange heat effectively. Visually inspect the radiator fins. If they are blocked, they must be cleaned using compressed air or low-pressure water, blowing from the inside out (opposite to the airflow direction). Check the coolant level in the expansion tank daily. Low coolant levels can lead to rapid engine failure. Inspect coolant hoses for hardness, cracks, or swelling. A burst hose under pressure will stop the machine immediately and can cause severe burns to personnel. Check the fan belt tension and condition — typically around 1 cm of deflection under a test load of roughly 4.2 kg on machines of this class. A slipping belt will result in poor cooling and poor alternator charging. HIT Srl can supply water pumps, thermostats, hoses, and belt tensioners for your machinery. We ensure that you have access to the right cooling components to keep your temperatures in check. Test the antifreeze concentration, especially before winter. Coolant also acts as a rust inhibitor inside the engine block. Listen for the fan clutch engagement. If the fan does not speed up when the engine gets hot, the clutch may be faulty. Overheating is a major killer of engines and hydraulic components. Regular cleaning and inspection are vital. HIT Srl supports your maintenance strategy with quality cooling system parts.
What should be checked when inspecting lubrication and radiator?
The thermostat regulates the engine temperature. In port operations, machines often idle for long periods. It is obvious that a stuck-open thermostat prevents the engine from reaching operating temperature, leading to "wet stacking" (unburned fuel in the exhaust) and sludge buildup. Monitor the temperature gauge. It should rise steadily to approx 85-90°C and stay there. If it fluctuates wildly or drops when driving downhill, the thermostat is failing. Check the top radiator hose. On a cold start, it should remain cool until the engine warms up, then suddenly get hot as the thermostat opens. If it warms up gradually, the thermostat is stuck open. If the engine overheats under load but cools down at idle, the thermostat may not be opening fully (stuck halfway). HIT Srl supplies thermostats and gaskets for all diesel engine brands. We help you maintain the thermal efficiency of your power unit. Replace the coolant when changing the thermostat. Old coolant loses its lubrication properties for the water pump seal. Running an engine too cold increases piston ring wear significantly. Fix it cheaply with a new thermostat from HIT Srl.
What does maintaining coolant expansion tank cap involve?
The expansion tank allows the coolant to expand as it heats up. The pressure cap raises the boiling point of the fluid. It is obvious that a faulty cap causes the engine to boil over. Inspect the rubber seals on the cap. If they are cracked, pressure escapes, and the coolant boils at 100°C instead of 120°C. Shake the cap. The vacuum valve should rattle freely. If it sticks, the hoses will collapse when the engine cools down. Check the plastic tank for stress cracks. Heat cycles make the plastic brittle, leading to sudden rupture. HIT Srl supplies expansion tanks, pressure caps (rated 0.7 to 1.5 bar), and level sensors. We keep your cooling system pressurized. Test the cap pressure with a radiator tester. If it opens too early, you lose coolant. Never open the cap when the engine is hot. Scalding risk. A $10 cap saves a $20,000 engine. Replace it regularly with HIT Srl stock.
What does maintaining engine water pump bearing and seal involve?
The water pump circulates coolant to keep the engine temp stable. It runs continuously. It is obvious that a seized water pump bearing will throw the drive belt, stopping the machine instantly and risking an overheat. Inspect the "weep hole" on the bottom of the water pump housing. If you see coolant dripping or a trail of dried coolant residue, the internal mechanical seal has failed. The pump must be replaced before it fails catastrophically. With the engine off and belt removed, wiggle the fan/pulley. Any play indicates the bearing is disintegrating. Listen for a growling noise from the front of the engine. This is often the water pump bearing running dry. HIT Srl supplies OEM-quality water pumps, gaskets, and coolant hose kits for this class of diesel engine. We keep your cooling system flowing. Check the drive belt tensioner. A tensioner that is too tight destroys water pump bearings. Always use the correct coolant mixture. Pure water causes corrosion and lubricates the seal poorly. Prevent roadside breakdowns by replacing weeping pumps with HIT Srl stock.
What does maintaining radiator shroud and seal integrity involve?
The radiator fan pulls air through the radiator. The plastic or metal shroud ensures the fan pulls air through the core, not from around the sides. It is obvious that a missing or broken shroud reduces cooling efficiency by up to 30%. Inspect the shroud for cracks or missing sections. If the fan is exposed, it moves air uselessly around the engine bay instead of cooling the water. Check the rubber seals or foam between the shroud and the radiator. If there are large gaps, the air takes the path of least resistance (the gap) instead of going through the fins. Check fan tip clearance. The fan should sit centrally in the shroud. If the engine mounts are worn, the fan might rub against the shroud. HIT Srl supplies radiator shrouds, rubber seals, and mounting clips. We maximize your airflow. A simple piece of plastic can be the difference between running cool and overheating. Ensure the fan sits at the correct depth inside the shroud (usually 50% in, 50% out). Optimize your cooling system with HIT Srl parts.
What does maintaining engine oil cooler integrity involve?
The engine oil cooler transfers heat from the oil to the coolant. It is a stack of plates inside a housing. It is obvious that an internal leak here mixes two fluids that should never meet. Check the coolant expansion tank. If you see "mayonnaise" (thick grey sludge), oil is being forced into the cooling system (since oil pressure is higher than water pressure). Check the dipstick. If the oil level is rising and looks milky, coolant is entering the sump when the engine is off. Inspect the external housing gasket. Leaks here drip oil down the side of the block. HIT Srl supplies oil cooler cores, housing gaskets, and O-rings for heavy diesel engines. We solve fluid mixing issues. Flushing the cooling system is mandatory after a cooler failure. Oil residue rots rubber hoses. Overheated oil loses viscosity and kills bearings. Maintain the cooler with HIT Srl parts.
How do I check coolant level safely on a machine with a pressurized cooling system?
Checking coolant level looks trivial until the system is opened while still hot. Start the check with the engine cold.
With the machine cold, open the engine cover and locate the coolant reservoir, usually a semi-transparent expansion tank mounted ahead of the radiator with a sight glass or level marks on its side. The correct level sits between the minimum and maximum marks. On machines fitted with an electronic coolant-level sender rather than only a sight glass, several platforms flag coolant as critically low once reservoir pressure drops under roughly 0.5 bar, and flag an overheat condition once bulk coolant temperature exceeds approximately 98°C, whichever trips first.
The reservoir cap and the sight-glass fitting are both wear items that HIT Srl stocks as direct-fit replacements.
Field note — HIT Srl, Reggio Emilia (Italy). Last updated: August 2026.
How often should engine coolant actually be tested and replaced?
Coolant condition should be tested on a much shorter cycle than the fluid is replaced. A typical schedule calls for testing coolant quality every 250 operating hours, and for a full replacement no later than every 2,000 operating hours.
The fill itself is not plain water. Machines of this type leave the factory with a roughly 50/50 mix of water and a heavy-duty ethylene-glycol antifreeze carrying a rust inhibitor.
HIT Srl stocks the coolant filter cartridge and the tank drain plug with its sealing washer as routine stock items.
Field note — HIT Srl, Reggio Emilia (Italy). Last updated: August 2026.
What should a routine check of the radiator and its hoses cover?
The correct sequence for a radiator inspection is a sight check of the radiator core, every union and every pipe, for integrity, secure fastening and an intact seal, done with the system cold and depressurised. On machines where the radiator carries an integrated oil-to-coolant heat exchanger for the transmission or hydraulic circuit, its own connections need the same check.
Where compressed air is used to clear debris from the fins or to blow-dry a union after a leak repair, keep the air pressure capped at roughly 2 kg/cm² (about 28 psi) and always wear eye protection. Before removing the radiator itself for deeper access, unbolt its mounting bracket rather than force the core sideways, and disconnect the hoses running to the oil exchanger.
HIT Srl carries the radiator mounting bushes, the hose clamps, and the heat exchanger's hose set as separate items.
Field note — HIT Srl, Reggio Emilia (Italy). Last updated: August 2026.
How do you correctly drain and refill the engine cooling system?
With the engine cold, open the drain valve at the lower part of the radiator and collect the coolant in a container rather than letting it run to the ground — used coolant is a regulated waste. On this class of machine the system typically holds in the region of 40 litres, so size the collection container accordingly.
Pour fresh water into the radiator to flush the circuit, run it briefly, and drain again; repeat until the water comes out visibly clean. Only then close the drain plug and refill with the correct coolant mix specified for the engine — never with water alone.
HIT Srl stocks the drain valve seal and the flexible fill hose used to top off the expansion tank as separate replacement items.
Field note — HIT Srl, Reggio Emilia (Italy). Last updated: August 2026.
Why does engine valve-clearance work require checking coolant temperature first?
Valve clearance is measured and adjusted cold: coolant temperature must have dropped below roughly 60°C before the covers come off. Before starting, put the machine in its safe service position and disconnect the battery isolator so nothing can crank the engine while the covers are open.
Where the cooling circuit needs to be drained to reach the head — for instance to access hoses running to an oil-to-coolant exchanger mounted near the engine block — drain the system through its dedicated plug rather than disconnecting hoses under residual pressure, and remove the hose clamps only once flow has stopped. If flushing is needed afterward to clear contamination before refilling, a coolant mix diluted to roughly 15–20% concentration is normally used for the flush pass, with the full-strength mix reserved for the final refill.
HIT Srl stocks the valve cover gasket and the hose clamps disturbed during this job as a small parts kit.
Field note — HIT Srl, Reggio Emilia (Italy). Last updated: August 2026.
What is engine coolant made of, and how must it be disposed of?
Engine coolant is a specific mixture of water, a corrosion-inhibitor compound, and, wherever freeze protection is needed, an antifreeze such as ethylene glycol.
Used coolant counts as a regulated substance almost everywhere it is drained, and it must never be poured into a drain, a sewer connection, or directly onto the ground; it has to be collected and disposed of according to the environmental rules in force in the country where the machine operates. The system also runs at meaningful positive pressure once the engine is warm, so any draining or disposal work should start with the engine cold. Where compressed air is used to help clear a drained circuit, keep it at or below roughly 2 kg/cm² and wear eye protection.
HIT Srl supplies coolant to the correct specification for this cooling system.
Field note — HIT Srl, Reggio Emilia (Italy). Last updated: August 2026.
What actually triggers an engine power derate linked to coolant temperature?
Diesel engine control units on this class of machine monitor the coolant-temperature sensor circuit continuously for two distinct fault conditions: an open or short circuit to the battery-positive supply, and a short circuit to ground. Either fault makes the reported coolant temperature unreliable, and the control unit responds by derating engine power progressively as the apparent temperature keeps climbing — starting at roughly a 25% power reduction and increasing up to a full 100% derate if the condition is not addressed, which in practice limits the machine to idle only.
The coolant-temperature gauge on the instrument panel is the operator-facing indicator of this reading.
HIT Srl stocks the coolant-temperature sensor and its connector pigtail as direct-fit parts.
Field note — HIT Srl, Reggio Emilia (Italy). Last updated: August 2026.
Why shouldn't a cold engine be put under full load right away?
Two service manuals for this class of machine converge on the same figure: don't apply full load until coolant temperature has reached approximately 80°C (176°F). One source frames it as a startup procedure — run the engine for about five minutes after starting, without fitting the pressure cap, until coolant temperature climbs past 80°C, so trapped air can work its way out of the system before the cap seals it in. The other frames the same threshold as an operating rule: let coolant temperature rise to the low end of its normal range, around 40°C (104°F), before doing any real work, and specifically do not apply full load before it reaches roughly 80°C (176°F).
HIT Srl supplies the pressure cap referenced in the warm-up step.
Field note — HIT Srl, Reggio Emilia (Italy). Last updated: August 2026.
When does the coolant mix actually need antifreeze, not just corrosion inhibitor?
A corrosion-inhibitor-only mix, without any freeze-point-lowering additive, is only acceptable where outdoor temperature stays above 0°C at all times, including overnight and during any off-season storage. Anywhere freezing conditions are possible, an ethylene-glycol antifreeze blend has to be used instead.
If the high-temperature cooling-system warning light comes on and stays on, the correct response is to check coolant level immediately and not continue operating the machine until the cause is found.
HIT Srl supplies the ethylene-glycol antifreeze blend for this cooling system.
Field note — HIT Srl, Reggio Emilia (Italy). Last updated: August 2026.
Why does the engine control system watch coolant temperature during a cold start?
Diagnostic routines on the coolant and intake-temperature circuits are deliberately held inactive during a cold start, and only re-arm once the engine has warmed past a defined threshold — otherwise a genuinely cold engine and a failed sensor would look identical to the control logic and trigger false faults.
Once the engine has reached normal operating temperature, walk the coolant circuit and check every hose connection for leaks, along with the fuel-line and oil-line connections nearby, since a warm, pressurised system will show a weeping joint that the same joint hid completely while cold.
HIT Srl stocks replacement hose sections for the connections nearest the engine block, and the connector pigtail for the coolant-temperature sensor.
Field note — HIT Srl, Reggio Emilia (Italy). Last updated: August 2026.
How often should the oil filter and oil of the auxiliary diesel engine be replaced, and the cooling system flushed?
Replace the oil filter and oil of the auxiliary diesel engine, and flush the cooling system, every 4000 operating hours, and at least once a year regardless of operating hours.
Why must nitrite-free glycol-based engine coolant not be mixed with a nitrite-based anti-corrosive agent?
The engine cooling system uses a glycol-based coolant that does not contain nitrite. This coolant must not be mixed with a nitrite-based anti-corrosive agent, because it may create slag and the cooling effect may be reduced. The engine coolant mixture is 50% high-quality monoethyleneglycol-based coolant and 50% water, mixed before being added to the system.
What conditions must be met before the diesel engine of a mobile harbour crane is allowed to start?
Before start, the engine requires: hydraulic oil tank taps open; coolant level not too low; coolant temperature not too high; the electric motor off, if present; pump coupler oil temperature below the engine-shutdown threshold; no emergency motor bypass code active, if present; the pump suction tap switch open, if present; no alarm for turret or truck emergency taps; no alarm from the fire control unit, if fitted; and the coolant temperature and diesel oil pressure sensors not both broken or disconnected at the same time.
What signals cause a mobile harbour crane's diesel engine to shut down after a delay, and what are the exact thresholds and delays?
The engine shuts down after a timed delay on: low boost pump pressure (3 s delay, 1.5 bar threshold); low boost pressure on winch 1 or winch 2 (10 s delay, 20 bar threshold each); oil coupler temperature above the stop threshold (3 s delay, 90 degrees C threshold); the safety hydraulic oil taps condition (3 s delay); fire alarm, if fitted; and low battery voltage (10 s delay, 21 V threshold). The engine also shuts down (after 10 seconds) on high or low coolant temperature/level, low diesel oil pressure (digital or analog), or a disconnected coolant temperature or diesel oil pressure sensor. If any of the delayed-shutdown sensors is disconnected, the engine will also shut down.
After a diesel engine shutdown on a mobile harbour crane, how long must the operator wait before restarting, and what special case extends this?
After the engine turns off, either automatically for safety or at the driver's will, it must wait 10 seconds before it can be started again. If the shutoff was caused by high pump-coupler temperature, the engine can only restart once that temperature has fallen back below the safety limit. If the coolant temperature is below the working threshold of 60 degrees C, no crane movement is allowed, unless bypassed with the block-movements code.
What are the maintenance items and intervals for this diesel engine at 400, 800 and 1000 operating hours?
Every 400 operating hours (or at least every 12 months): drain the fuel tank sludge collector, and check/adjust the alternator belt and battery electrolyte level. Every 800 operating hours (or at least every 12 months): check the charge air pipes for leaks, and change the fuel pre-filter and fuel filter. Every 1000 operating hours (or at least every 6 months): change the coolant filter (not concurrent with a full coolant change).
What is the coolant system overhaul interval on this diesel engine, and what does it involve?
Every 48 months or every 10,000 operating hours: check and clean the cooling system, and change the coolant.
What are the possible causes of excessive or insufficient coolant temperature on this diesel engine?
Excessive coolant temperature can be caused by: excessive coolant temperature conditions themselves being present (blocked flow), low coolant level, air in the fresh water coolant system, a malfunctioning circulation pump, or a defective thermostat. Insufficient coolant temperature can be caused by a defective thermostat.
Looking for step-by-step procedures? See Engine & Cooling Procedures.