too much crank case pressure...., how can you tell? Options

[jr91472]

So a little history. I am struggling with a rear main seal that doesn't want to stop leaking oil (sounds like I am not the only one).

I am down to two possibilities (that I know of)
1. excessive wear on the flywheel hub
2. excessive case pressure

Focusing on #2, how can you determine if there is too much pressure?

One mechanic told me that one test is to simply place the oil filler cap on the oil fill neck (without tighting) while the car is idling. If the cap blows off = too much pressure. Anyone heard of this?

Ultimately, what is the cause of excessive case pressure? and how do you fix it?

sorry for all the newbie questions, but these things keep me awake at nite......

(IMG:http://www.914world.com/bbs2/html/emoticons/beer.gif)

[Dr. Roger]

Hey JR,

Here's the quick and easy way to see is it's excessive "blow-by" pressures causing your oil leak.

Block wheels so car doesn't move.
Remove the dipstick.
Start the engine.
If oil doesn't start spewing out of dipstick, then note if air is coming out of dipstick hole. {I, VERY CAREFULLY, use my finger.}
If there is a lot of air coming out of the dipstick hole then you probably have a "blow-by" problem.

Blow by can come from either the rings or the valves.
Note: excessive crankcasr pressures can also be caused my a blown head gasket on some engines.

As Flat 4 engines do not have valve cover access openings there is no quick way to tell which might be your problem.

You need to do a leak down test for that.
"What's that" you may ask?

It is where by pressurizing the combustion chamber when a cylinder is at TDC and noting is air gets by the rings or not. AKA, listening at the oil filler opening with your ear.

Valve bypass is heard at the opening in your valve covers. If you had them. Whick you don't. =-)

If you find little air coming from the dipstick or oil filler openings, then it's your rear seal.

Best of luck.