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Yuchai 4D24/4D24T Diesel Engine Maintenance

Dec. 19, 2019

4.2 Maintenance of Yuchai 4D24/4D24T diesel engine

The initial maintenance should be made and recorded according to the warranty manual.

During the use of diesel engines, the following requirements should also be carried out for routine maintenance, daily maintenance by the user own, other levels of maintenance by professional maintenance person:

Air filter is a key component to ensure the diesel engine clean air inhaled, to always check the air intake system and maintenance, to replace the air filter, ensure that the diesel engine does not appear early wear.

4.2.1 Diesel engine breaking-in

The new diesel engine need to have breaking-in period (starting 50h), in order to make the match performance of each moving parts to further improve, ensure the working reliability and service life of the diesel engine:

1) After starting the diesel engine in low speed to warm up for at least 5 minutes;

2) After starting, the load cannot be increased sharply, it needs to slowly increase;

3) Diesel engine idle speed or full load running not more than 5 minutes;

4) Often observe the oil, water temperature meter, to ensure the normal working status of the diesel engine:

The overhauled diesel engine, also need to have breaking-in period (refer to new machine breaking-in), to ensure of the friction pairs matching effect. After the end of the breaking-in period oil should be replaced, and replace the oil filter element. No idle running, which resulting in early wear and tear.

4.2.2 Maintenance of diesel engine

Correct, timely and careful maintenance can guarantee diesel engine working smoothly for a long time, to prevent the occurrence of fault, reduce wear, prolong the service life. The user should according to the content listed in diesel engine maintenance, specific classification as follows: Maintenance cycle of the table below:

Note: the use of harsh conditions (minimum temperatures below -20°C, or the highest temperatures higher than 35°C, or environmental dust content in the high desert, mine site, construction sites, coal yards, etc.}, it is necessary to shorten the replacement cycle of engine oil.

Yuchai engine maintenance cycle time

Diesel engine daily maintenance instructions

Good maintenance from day to day of diesel engine and its system are beginning to understand, starting diesel engine before check the oil level and coolant level, check whether there is:


The loose and damaged parts

The belt is worn or damaged

Any change in the appearance of the diesel engine

No fuel smell

At the same time need to see if there is no fault lights on, if there is a fault then need to identify, if it is historical failure, can be cleared.

This section describes the daily maintenance instructions of some of diesel engine system and parts.

5.1 Coolant level check of cooling system

Coolant level check 


Warning: Do not open the radiator pressure cap from the hot diesel engine, should wait for coolant temperature below 50°C to open the pressure cap, otherwise high temperature coolant or steam spray may cause personal injury.

Warning: Coolant is poisonous to avoid contact with kids or pets. If it is not be used anymore, it should be treated according to the local environmental regulations.

Warning: Do not use corrosive cleaning agents in the cooling system, otherwise it will damage the aluminum parts.

Attention: Do not use the seal additive to solve the cooling system leakage problem. This will cause the cooling system block and the coolant flow is not smooth, thus causes the engine overheat.

The coolant level must be checked every day.

Attention: Do not add a cold coolant to the hot diesel engine, otherwise it will damage the Diesel  Engine Castings, wait until the diesel engine temperature below 50°C. then add coolant. Adding coolant to the diesel engine must be mixed with the correct proportion of antifreeze, auxiliary coolant additives and water to prevent damage to the diesel engine.

Fill the coolant to the bottom of filler, of the radiator or expansion tank.

5.2 Cooling fan

The user every day should visually inspect cooling fan. Check for cracks, loose rivets, curved blade or loose. Check the fan and ensure it is installed firmly. If necessary, tighten the bolt.

Warning: Do not rotate the diesel engine by pulling or prying fan. Otherwise it will damage the fan blade, resulting in fan fault and caused personal injury or property loss, should use accessory drive shaft and the crankshaft turning tool to rotate the crankshaft.

Warning: Do not attempt to bend the blades of the fan or continue to use the damaged fan, bending or damaged fan blades cannot work property, and will result in personal injury or property damage.

5.3 Fuel filter

Warning: Discharge the water in the fuel filter (pre filter) to the container, and handle it in accordance with local environmental regulations.

RAYWIN required the user to install the fuel filter (pre filter and fine filter) or fuel-water separator. daily discharge water of fuel filter (pre filter) or water in oil-water separator and sediment in the fuel supply system.

Attention: Lose the discharge valve, the valve will not be overdone, excessive tightening will damage the thread.

5.4 Check oil level

User should check the oil level before each starting.

Attention: It is strictly prohibited to running the engine in oil level below or above the oil limit marks, which can lead to diesel engine performance degradation and damage of diesel engine.

schematic diagram oil dipstick

The precise reading can be measured after diesel engine shutdown. At least until diesel engine downtime longer than 15 minutes, then began to check the oil level. This period of time can let the oil back to the bottom of oil pan.

Warning: Used oil has a carcinogenic effect, and may produce reproductive disease, should avoid the inhalation of oil vapor, do not swallow and prolonged contact with the used oil, if no longer use should be handled in accordance with local environmental regulations.

Warning: In order to reduce the possibility of personal injury, should avoid the skin direct contact with hot oil.

5.5 Drive belt check

Tightness of the belt cannot be too loose or too tight, too loose will reduce the transmission efficiency of the water pump, the rotation speed of the fan and the charger is not enough, influence the cooling effect. At the same time too-loose belt produces vibration will cause belt and pulley unnecessary wear, too tight, it will influence the belt and bearing parts service life.

5.6 Air filter

Users can observe the air resistance indicator to judge the air cleaner clogging which installed on the intake pipe of the air filter, when air resistance indicator changed from normal green to red, it indicates that the air intake filter resistance exceeds the limit value, and air filter need to be cleaned or replaced.

air filter

Attention: The engine is absolutely forbidden to work in case of air filter failure or without air filter. The intake air must be pre-filtered to prevent dust and impurities, otherwise caused engine early damage.

5.7 Valve

In order to ensure the normal working status of diesel engine, the user should regularly check and adjust the valve clearance. In the cold status, the clearance of the intake valve is 0.2±0.05 mm, the clearance of the exhaust valve is 0.2± 0.05 mm.

Valve clearance checking and adjustment method is:

The crankshaft turns to the first cylinder compression top dead point position, then you can check and adjust the l,2,3,6 valve, after then the crankshaft rotates 360 degrees, then you can check and adjust the 4,5,7,8 valve. Valve clearance adjustment can be carried out by adjusting valve and adjusting screw. First loose lock nut, screw in or out with screwdriver, then check the rocker arm and the valve clearance with feeler, and tighten the lock nut after meeting the requirements.

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