Engine oil in antifreeze: why a malfunction occurs

The device of an internal combustion engine assumes a constant supply of lubricant to various elements and assemblies, as well as effective cooling. To solve the problem, special channels are made in the cylinder block and cylinder head through which the working fluid of the cooling system (cooling jacket) circulates , as well as the oil channels of the lubrication system . Visit this link to gain more ideas: oil in coolant reservoir


It is important to understand that this problem is serious, and the engine itself needs immediate repair. In this article, we will look at the main reasons why oil appears in the engine cooling system, and also talk about the available diagnostic methods to eliminate such a breakdown of the power unit.

Oil in the engine cooling system: causes

So, the ingress of lubricant into the engine cooling system is most often determined when checking the coolant level in the expansion tank . As a rule, the color of  antifreeze or antifreeze in this case changes, you can see oily spots on the surface. Also, there are residues of a mixture of oil and antifreeze on the tank lid and its neck. The liquid level itself can be lowered.

Additional signs include the appearance of thick white smoke from the exhaust system when the engine is running. If you remove the oil filter , then sticky deposits can also be seen inside it. Depressurization is also indicated by the change in color of the oil itself on the dipstick, emulsion and foam on the oil filler cap.


Such signs clearly indicate that the engine oil has gone into the cooling system. Immediately, we note that this problem requires special attention, since oil and antifreeze are fluids for different systems. This means that normally the channels through which they circulate do not communicate with each other. In other words, a serious leakage has occurred.


Given this information, a number of main possible reasons can be identified for which oil gets into the antifreeze:

·         problems with the oil cooler;

·         heat exchanger malfunctions;

·         breakdown of the cylinder head gasket ;

·         damage and defects of liners in the business center;

·         cracks affecting channels in a block or head ;

·         pump malfunctions , etc.


Taking into account the fact that during the cooling of the engine, the liquid in the cooling system is under pressure (and this pressure is higher than in the lubrication system), coolant can gradually enter the lubrication system through leaks.

You also need to understand that coolants that are developed for modern engines contain a whole package of active chemical additives. These additives resist scale formation, clean the cooling system and also resist corrosion.


For this reason, it is recommended to fill the engine with only the recommended coolant, dilute the concentrate with distilled water in the required proportions, avoid mixing different coolants, and also make timely replacement and preventive cleaning of the radiator and cooling system .

This approach allows not only to keep the system clean and maintain its maximum performance, but also significantly reduces the risks of deep (through) corrosion of metal elements.

 If oil gets into antifreeze: consequences for the motor

It is quite obvious that the oil in the expansion tank is an alarm signal, and in this case there are much more risks not for the cooling system itself, but for the engine. In other words, if the lubricant enters the cooling system, then the antifreeze will also enter the lubrication system.


It is not difficult to guess that when mixing two types of fluids that contain packages of active additives, an unpredictable and uncontrolled chemical reaction occurs. The result is a deterioration in the properties of the lubricant and coolant, an increased contamination of both the oil channels and the channels of the cooling system occurs.