Why the diesel engine warms up

Why the diesel engine warms up

Malfunctions may occur during the operation of any internal combustion engine, which lead to overheating of the gasoline or diesel engine. For a diesel engine, overheating is a more serious problem compared to gasoline counterparts, since a critical increase in temperature can quickly disable a diesel engine due to a number of design features of the unit.

We also recommend reading the article about it, what temperature is considered working for a diesel engine. You will learn from this article, why indicators of the optimal operating temperature of a diesel internal combustion engine differ depending on the specific type of engine.

Consequences of overheating

Slight and short-term overheating of the motor, which is noticed in time, allows you to minimize the risk of serious consequences. In other cases, overheating of the diesel engine causes great damage to the power unit.

Steam plugs are formed in the cooling system, as a result of which the cylinder head overheats. The result of severe overheating of the diesel engine is the deformation of the cylinder head and the breakdown of the sealing gasket. The head of the unit "leads" from high temperature, the tight fit of the cylinder head to the cylinder block is disturbed.

A significant increase in temperature can also lead to cracks in the cylinder head and cylinder head, impermissible expansion of parts in the internal combustion engine design. In such cases, the motor will simply jam. After cooling, overheated diesel will become unsuitable for further operation. Expensive diesel engine repair or even a complete replacement of the unit is required to restore engine performance.

Causes of diesel engine overheating

Diesel can overheat for various reasons. The cooling system is responsible for maintaining the operating temperature of the diesel engine within strictly limited limits. In order to control and detect an intense increase or decrease in engine temperature, there is a separate indicator on the dashboard of most cars.

As practice shows, it is not always possible to detect deviations from the norm in a timely manner during movement. You should also take into account possible malfunctions of the diesel engine temperature sensor or the indicator on the instrument panel. Direct and indirect signs of diesel engine overheating can serve:

  • constant operation of the fan of the cooling system at the maximum speed of rotation in idle mode (if there is an electric drive);
  • increase in the level of noise and vibrations during the operation of the internal combustion engine, power drop, detonation knocks;
  • the appearance of white steam from under the hood, which became noticeable during the ride;

Low level and coolant leak

One of the most common causes of overheating is a lack of coolant in the cooling system of a diesel engine. Coolant tends to evaporate over time, as the constituent component is distilled water. In this case, it is necessary to add water or dilute the concentrate with antifreeze/antifreeze in the required proportion, and only then pour the resulting mixture into the expansion tank.

Carefully! It is strictly forbidden to check the level and add coolant to the expansion tank before the engine cools down. Increased pressure is created in the cooling system, as a result of which the liquid can splash out of the filler neck and cause serious burns.

It is also forbidden to pour liquid into a hot engine, in order not to damage the engine due to the temperature difference between the heated power unit and the fresh coolant. If an intense drop in the level is noted after topping up the coolant, then you should visually inspect the nozzles and connections, radiator, the expansion tank itself, as well as the location of the water pump (pumps) cooling system for cracks or other damage, as well as leaks.

Cracks in the cylinder block or in the cylinder head can be another reason for the drop in the coolant level, as well as damage to the block head gasket. If these damages affect channels, through which the coolant circulates (engine cooling jacket), then part of the liquid from the cooling system can enter the cylinders of the diesel engine, as well as in the diesel engine lubrication system.

We also recommend reading the article about it, why a diesel engine can smoke white exhaust. From this article, you will learn about the possible causes and methods of diagnosing the malfunction.

Radiator and thermostat

If the coolant level is normal, but the engine temperature is significantly higher than the permissible one, then overheating of the diesel engine may also be associated with a decrease in the cooling efficiency of the liquid in the radiator. Contaminated "honeycombs" of the radiator do not allow this element of the cooling system to carry out heat exchange normally. In this case, the radiator must be thoroughly washed.

Diesel can overheat due to thermostat malfunctions, namely, when the thermostat of the diesel engine jammed to open. A permanently closed thermostat does not open as the engine temperature rises, forcing the liquid to move only along a small circuit (small circuit). This means, that the coolant does not pass in a large circle through the radiator) for cooling.

Other malfunctions

A critical increase in diesel engine temperature can be caused by malfunctions of the cooling system fan or the diesel engine temperature sensor. Another cause of diesel overheating is severe contamination of the internal channels of the cooling system, which prevents the normal circulation of the coolant.

It is also worth noting the incorrect adjustment of the fuel injection advance angle. For this reason, the temperature of the exhaust gases rises sharply, as a result, the total temperature of the diesel increases, especially under load. The pump deserves special attention. Destruction of water pump blades and other breakdowns reduce the efficiency of coolant circulation in the system and cause diesel engine overheating.


The fact of overheating of the diesel engine requires an immediate shutdown of the unit to find out and eliminate the causes. You should start checking the efficiency of diesel cooling with your own hands from that, that the engine must be allowed to cool down on its own.

Next, you need to check the coolant level in the tank, as well as conducting a thorough visual inspection of the expansion tank itself, of all nozzles, radiator cooling radiator heater, as well as pump mounting areas to detect possible leaks.

The next step is to check the thermostat. To do this, it is necessary to start the cooled engine and monitor the increase in temperature. With heating, the thermostat should open for coolant, which moves in a small circle, access to the radiator (great circle). If the thermostat is stuck, then the lower hose will be cold. It's easy to install yourself, carefully feeling the nozzle with your hand and assessing the heating of the hose.

The last step will be to check the operation of the fan drive. It is necessary to make sure that the electrical contacts are functional. In addition, it is necessary to look into the fuse block, since a faulty fuse can also cause the fan to turn off and the internal combustion engine to overheat.

Warning! In the process of checking the cooling fan, it is necessary to observe safety measures. The fan may unexpectedly start rotating at high speed, resulting in probable limb injuries from a shovel blow.


If severe overheating of the diesel engine occurred at a negative temperature overboard, then keeping the hood open for accelerated diesel cooling is not recommended.

In order to get to the nearest service station with a faulty thermostat, you can independently remove the valve from the diesel engine thermostat housing. This will allow the coolant to circulate in a large circle through the radiator all the time, which will not allow the engine to reach operating temperature.

In the absence of an opportunity to identify the cause of diesel overheating, eliminate the malfunction, to deliver the car on a tow truck or a tow truck, you can try to continue driving on your own. To do this, you need to be absolutely sure that the internal combustion engine temperature sensor and the indicator on the instrument panel are working.

Allow the engine to cool, then they start and move on cars with minimal loads. Movement is carried out until that moment, until the diesel engine temperature exceeds approx 2/3 from the permissible working limit. After the temperature rises to the specified limit, the driver immediately turns off the ignition (under no circumstances removing the key from the ignition switch) and continues the movement by inertia in neutral gear with a speed of no more 30-40 km / h.

This method is a last resort, which requires increased caution. Keep in mind, that the vacuum brake booster system (after 2-3 ducks) and power steering will not work when the engine is turned off. When moving down a slope, it is necessary to smoothly engage the gear, corresponding speed of movement. If there is a need to slow down, then, at the same time as pressing the brake pedal, the reduced gear is switched on. In the process of such inertial movement with the engine turned off, the diesel has time to cool down, after which the motor or starts again, or the car stands on the side until the internal combustion engine has completely cooled down.

Finally, let's add, that it is not recommended to use the described method of independent movement on cars with an automatic gearbox, since in parallel with the existing problem of overheating, various malfunctions of the automatic transmission may be added as a result of incorrect operation when driving with the engine off.

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