Not so many people know that very important to change crankcase oil separator on BMW M52 engines, because it can be the cause of big problems, especially in winter time, like in Lithuania.
Why it needed
When the pistons move up and down, they also create compression in the crankcase. The engine oil has vapors and the pressure causes them to go up. On the old days they used to be vented into the atmosphere but now they’re vented back into the combustion chamber.
The vapor go through a separator because they can contain some oil and that’s something you don’t want going back into the engine. Once that’s separated, the vapors, which contain some hydrocarbons, flow into the intake manifold and into the combustion chambers. The amount of vapors going into the engine will depend on engine vacuum.
To test if it works
The test for a failed valve was simply remove the dipstick and see if air sucks in, or the engine changes pitch. With the engine idling, I removed the dipstick and the air rushing in, not only changed the pitch of the engine, but it died.
Changing
It is possible to change by it self without removing intake manifold. But then be very careful on vacuum pipes. Very difficult to put them back correctly.
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