Coolant in engine oil: causes and cleaning of the engine

Coolant is a fluid that is used to carry heat generated in the engine to the radiator where the heat is exchanged with atmospheric air. 

Engine oil is used to lubricate moving parts in the engine to reduce friction and wear. It also plays a major role in cooling the engine. About 30% of engine cooling is done by the engine oil.

If you open the engine's oil cover and find mayonnaise or signs of coolant when checking oil level on your oil dipstick, you have coolant in the engine lubrication system.

The earlier this issue is detected and fixed, the better.We wrote an article earlier on coolant mixed with oil in the cooling system and how to clean the cooling system.

The article contains causes of oil mixing with coolant in the cooling system which also applies to this scenario (oil mixing with coolant in the engine). In addition to those, flood water can enter the engine. We advice that you take a look at that article before proceeding to read this one.

Assuming that you have read the article through the link above, we will go straight to how to clean the engine when coolant has mixed with engine oil.

Whether the cleaning will be successful or not depends on the severity and how timely the issue is being resolved as storing the engine with water in it can cause serious corrosion damage inside the engine.At very early stage of the fault, a vigilant car user might notice bubbles of coolant on the oil dipstick when checking the oil level but if the issue is not resolved on time, the water in the oil increases and causes it to emulsify to form a gelatinous substance which some people refer to as mayonnaise (not the edible one).

How to clean the engine internals due to coolant mixing entering the engine's lubrication system.

The first task before the cleaning begins is to identify the root cause of the problem. If the cause is a head gasket failure, opening the engine to fix a new one presents an opportunity to clean the engine's internals properly. Even if that is done, we still recommend flushing the engine at least once after it has been coupled back. This is becauase not all the engine's internal part can be reached for cleaning. In essence, identifying and fixing the cause is key.

If we have no opportunity to open up the engine, follow these steps to flush the coolant out of the engine.

1. Open the oil filler cap and remove the oil drain plug for the engine oil to drain out.

2. After the oil has stopped draining from the drain plug, loosen the engine oil filter.

3. Put a new engine oil filter.