wannawagon

2008 GL320 with huge blowby. Only got about 180kkm on it. In Australia so no DPF

I have had a few of the om642 motors (normally higher km) and never had this issue

I have put a catchcan on it (years ago) and can feel pressure in the hoses (from pcv) but the oil filler cap has way more pressure.

I have to travel a few hundred km to get home so have routed the catch can vent out the right wheel arch so as to limit oil going into turbo (and intake) and have bought a heap of oil

No visible smoke out exhaust

I remember looking at a gl320 years ago at auction with similar high crankcase pressure but i just decided to pass on it so never knew diagnosis

any thoughts appreciated

kajtek1

How big is it?
Will napkin stay on fill hole while engine idling?
How about cardboard?
My OM642 has 216k miles and blowby is minimal.

wannawagon

sorry about delay. The blowby is pretty bad. When I remove filler cap I hear a pop and oil is pushed up the dipstick tube. If I put a rag over it I think it will just create more mess

I am going to try and vent from pcv straight to atmosphere and see if reduces back pressure. I remember the catch can I put on has a screen which may have been blocked

pretty sure the cause of the obvious leak was the dipstick moving out a little. Like if you pull it out a mm oil pours out.

John CC

I'm confused. Wouldn't removing the fill cap relieve any pressure in the crankcase? Seems with the cap on the dip stick would be pushed out, along with the oil. Am I missing something?

wannawagon

should have been a comma in there. If cap is on the oil comes out the dipstick tube if not fully in housing.

kajtek1

That's pretty obvious signs of something wrong with pistons, or rings.
You can run smoothest test, to pinpoint the cylinder and take snake camera to look inside.

wannawagon

not sure on “Smoothest” test. Is that a compression test?

The lack of blue smoke out the exhaust is a bit baffling to me.

thought if I had scored bores I would have oil smoke.

wannawagon

not sure on “Smoothest” test. Is that a compression test?

The lack of blue smoke out the exhaust is a bit baffling to me.

thought if I had scored bores I would have oil smoke.

kajtek1

Good scanner will make the test for you.
there are 2 of them
1 simulated compression test
2 injector test
You need #1 for sure.

wannawagon

Will chase up a better scanner - wow didn't think a scan could do compression - many thanks

John CC

It doesn't actually measure compression pressure. It measures angular acceleration and deceleration of the crankshaft while cranking with the starter and deduces compression from that.