Oil in the cooling system and a burnt out heat exchanger

At many service stations that do not specialize in this brand, and who do not know about such a "trouble", they often sentence a car to "capital". This is, at least, "removing the cylinder head, replacing it, grinding it, replacing the accompanying gaskets. Such repairs cost a pretty penny to the owner, but disappointment intensifies when the problem persists after such repairs. Therefore, do not rush, perhaps the reason lies in the burnt out heat exchanger... It attaches to the side of the motor and is not easy to reach. The heat exchanger is a kind of radiator for the engine oil system. To know more, check out: oil in coolant reservoir
It is usually not large in size and has 2 circuits, the 1st is the circuit through which the oil flows, and the 2nd circuit, in which the coolant. The oil pressure in the engine is greater than in the cooling system, therefore, when the heat exchanger wall burns out, the oil is pushed out by pressure into the antifreeze circuit. Further, the oil floats in the coolant expansion tank, which is very frightening for car owners.

It happens that the reason for the appearance of oil in the antifreeze is a gasket that is installed between the heat exchanger and the cylinder block.


On the surface of the heat exchanger, on the reverse side, grooves even form, and oil under pressure penetrates into the coolant. A similar gasket is installed on the oil cup in Bavarian engines. These heat exchanger gaskets are commercially available, so it makes sense to replace them first.


The manufacturer recommends draining the engine oil from the engine before removing it, but from practice, if everything is done carefully, then very little oil is poured out, and antifreeze does not enter the oil system.

Coolanthave to be drained completely. On 535d in the back of an e60 it took 3-4 hours to replace the heat exchanger and gaskets, which are mentioned above. Why is it better to change it to a new one? Even after removing the heat exchanger, it is very difficult to check it. Attempts to pressurize it and check for leaks usually do not give a result, supplying several bars to the circuit, it seems that the leak is not found anywhere. Probably, the leak appears only "hot", the metal expands and the crack increases. This part is commercially available not only in the original version, and is not so expensive when compared with the price for overhauling the motor.


There is an option to buy on "analysis" used. repair, but no one will give a guarantee that it is serviceable, and the cost of replacement may exceed the cost of the purchased spare. It will be so sad to know that after such an installation the problem will not be solved.


Such a breakdown is especially dangerous for motors in "fives" e60, tk. there is no engine temperature indicator on the dashboard in this model, and when a lot of oil accumulates in the cooling system, it is easy to "boil". You can find out about overheating only when the corresponding red "light" comes on, but it may be too late. Therefore, it is better to check the condition of the antifreeze in the expansion tank from time to time.