vacuum leak at M50 valve cover- 12 inHg at intake

[werminghausen]

I have a 12 inHg reading at idle- I think 17-22 inHg are spec.
I just did some testing on the car.
I took off the little 3 millimeter hose right underneath the 12 mm where it ends in the valve cover right above the oil filter (I don't know what these hoses all do there- probably inhaling vapors coming from the crankcase and burning it).
Funny, but when I took the 3mm hose off the fitting and tested vacuum on there I had straight 20inHg. When I put the hose back on the valve cover it was back to 12 inHg.
The leak is coming from the valve cover. I have no oil leaks at the valve cover. Any ideas?
Can this also be a reason for bad mileage- 17mpg?

Martin

[Ross]

Check the gasket on the filler cap.

[werminghausen]

I have a new filler cap for the engine oil.

[rob101]

I have a 12 inHg reading at idle- I think 17-22 inHg are spec.
I just did some testing on the car.
I took off the little 3 millimeter hose right underneath the 12 mm where it ends in the valve cover right above the oil filter (I don't know what these hoses all do there- probably inhaling vapors coming from the crankcase and burning it).
Funny, but when I took the 3mm hose off the fitting and tested vacuum on there I had straight 20inHg. When I put the hose back on the valve cover it was back to 12 inHg.
The leak is coming from the valve cover. I have no oil leaks at the valve cover. Any ideas?
Can this also be a reason for bad mileage- 17mpg?

Martin

perhaps the O-rings in the dipstick?

[werminghausen]

can there be any other potential weak point for leakage in the valve cover/crank case?
I checked dipstick o-rings and oil cap. Blitzkrieg mentioned the o-ring at the plastic fitting where the 3mm vacuum line enters the valve cover together with the 12mm line. i will check this out tonight.
My assumption is that the engine draws some wrong air form the crank case but how bad is this long term?
I checked a couple of rubber lines around the intake, most are old, some fall apart.
I decided to exchange all the hoses/lines around the intake.
Is there any manual out how to take the intake manifold out?
Martin

[Ross]

Fresh air can enter at any of the seals or gaskets.
That sort of leak admits unmetered air so will effect your mixture, leaning it.
O2 sensor will tell the computer to add more fuel.

[werminghausen]

I am searching for the leak coming from the valve cover. Who knows about how many openings there are that might leak. I have no oil leaks
I checked oil filler cap. dip stick and the fitting with o- ring where the 3mm and 12mm hose are connected to the valve cover.
I took the 3mm hose off and closed it.
What is the 12mm hose good for?
looking for help
Martin