Hello,
Finally spring and time to give my 244 some tlc. I've noticed a build up of dried oil under the valve cover gasket and thought I'd check for excessive crankcase pressure. I held some plastic tight over the oil filler opening while my boss turned the car on. The plastic started to flap up and down like crazy and it sounded like a little enging itself until it busted. Don't seem right to me. I thought it would get sucked in slightly showing some vacuum. What do you think?

Thanks!

John Mpls

Mine is doing the same exact thing, paper flapping up and down like crazy oile leaking from my fill cap. I checked my flame trap it is clear but I could not blow through the oil separator box it is totally clogged I am hoping this is the problem.
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Dean 1991 240 wagon

Dean, IMHO the test is bogus.

Like trying to gauge sea level in a storm, the pressure wave peaks and valleys created by normal piston turbulence in a small place make the average very difficult to measure without a highly damped manometer. Most of the success folks had using the heavy metal oil filler cap is based on its inertia. No normal PCV vacuum is going to take all instantaneous pressures below atmospheric.

I kinda figured Kyle's comment was meant to stir up some discussion of our board's oil cap mythology.
--
Art Benstein near Baltimore

It's always darkest before dawn. So if you're going to steal your neighbor's newspaper, that's the time to do it.

Thanks Art!
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Dean 1991 240 wagon

Good to know. Seems like what happened to me was not unusual then. Let me know how things work out. I'll probably be working on it this weekend unless we get more effing snow..

John

So I guess I know what I'll be doing this weekend...

Figured it was wrong but never done it before so I was not sure. Well it's a good reason to buy the compression tester that I've wanted for so long.

Take it easy guys,

John

The best test to start is the cheapest -- on a warmed up engine, simply some cellophane (plastic food wrap, the static cling kind) held tightly (you don't want it sucked in) around the mouth of the oil fill opening -- wear gloves to you don't burn your fingers. If the cellophane bends inward, you don't have any problem; if it bulges outward, you have to do further tests.

Older cars (up to the B23, with the flat valve cover and heavy metal cap) can do a jiggle test in lieu of the cellophane, but your B230 doesn't test reliably (the cap is too light), so the cellophane is necessary.

If your results are good, that doesn't mean that you shouldn't regularly check your hoses and flame trap.

Thats how I did it and plastic went between concave and convex very rapidly. I have not been able to check for clogged breather system yet. Could it be anything else?

Thanks for your response

Crankcase pressure is developed by normal operation blow-by past the piston rings. It will build if it is prevented from escaping through the PCV system, thus the need for a clean free-flowing PCV system.

If you find high and uneven positive pressure in the crankcase, something is not right.

Were it me, my next step would be to run a compression test, both the dry and the leak-down versions. If one cylinder is suspiciously low, its rings might be the cause of your excessive pressure. If the leak-down test raises the readings, it's a good sign of weak ring(s).

Good Luck,

Bob

:>)

Hope this is not hard to follow.

A piece of paper, or plastic as you used should be pulled down against the oil filler cap opening. Even your hand can be used to feel for the slight vacuum that should be there.

A healthy system will have a free flowing oil separator box connected to a clean flame trap. All of the hoses involved as well as the brass nipple on the manifold need to be inspected to insure they are not restricted or clogged. A drill bit of the proper diameter makes it easy to clean the opening in the brass nipple. Hoses can be replaced.

All of the procedure is outlined in the FAQ's.

Randy

Benzo,


Thank you for the interesting story,


Goatman