1995 525it, M50: excessive engine oil consumption

[werminghausen]

My M50 is burning a lot of oil, like one quart of engine oil every second tank. There is no visible smoke from the exhaust and there are no oil spills on the driveway. The engine has 180K miles and is generally in decent shape.
I wanted to ask the question in the forum: What might be the reasons for burning so much oil and what can I do?

[Tiger]

I'd have to say it might be the PCV unit. When this unit goes bad, it lets too much oil into engine. I am working on my intake manifold and I pulled out the old PCV... lots of oil and it gunked up my intake manifold and fuel injectors with oil

[werminghausen]

I'd have to say it might be the PCV unit. When this unit goes bad, it lets too much oil into engine. I am working on my intake manifold and I pulled out the old PCV... lots of oil and it gunked up my intake manifold and fuel injectors with oil

Thanks Tiger... What exactly is the PCV unit and what is it doing or not doing in my case? I have pulled my intake maifold last summer and there was some oil present but not too crazy. Manifold was not gunked up really.

[whiskychaser]

What are compressions with/without a tsp of oil down the plug hole?

[John in CT]

where do I look?

Thanks,

John

[werminghausen]

What are compressions with/without a tsp of oil down the plug hole?

I have not tested compression.
What does compression tell me? In order to test... How can I easily disconnect fuel injection: disconnect fuel pump or fuse?

[whiskychaser]

Compressions tell you if your engine is worn and thus burning oil. The idea of the drop of oil is to form a temporary seal on top of the piston to see if the compressions improve. You can remove the pump fuse and run it until it dies. But there may still be some pressure in the system even after that.

[werminghausen]

Compressions tell you if your engine is worn and thus burning oil. The idea of the drop of oil is to form a temporary seal on top of the piston to see if the compressions improve. You can remove the pump fuse and run it until it dies. But there may still be some pressure in the system even after that.

Thanks, this makes sense. I'll run then 2 compression tests: 1 without oil and another with oil and see what the difference is. I'll report back. I guess the engine should be warm for the compression test.

[whiskychaser]

Thought I just replied to this but my answer isnt there :-( Just a brief word of caution. When I did my compressions I removed the plugs when cold, cleaned plug and head threads, refitted and warmed up the engine. Then removed them again and did the tests. There is a small risk you could strip a thread on an ali head if you install/remove plugs when its warm. Hence my rather roundabout method