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......

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[Mueller]

all motors are going to have crankcase pressure, figure you have the pistons going back and forth moving tons of air and you have the crank and rods acting like fans inside the crankcase, this normal, as is a little bit of blow-by from the piston rings, too much blow-by and that is bad, signs would be your oil getting dirty faster than normal.

the crankcase must have ventilation, adding vents to the valve covers/heads is a good idea as well (factory did this on some models, I'm guessing for smog reasons they stopped it)

do a search and you'll solutions for adding "puke" bottles and the like.

for venting, you can vent to atmosphere, and/or vent to the aircleaner to help "suck" the air out of the crankcase....only problem with the second method is that if too much oil vapor gets ingested, it has an effect that is similar to lowering the octane of you fuel (the oil vapor displaces air)