Re: WHat causes pressure in the valve cover?

[adamnelson@juno.com]

As far as I know, a lot of the pressure can be from worn valve guides.
The pressure leaks from the exhast port through the valve guides. The
other way for pressure to accumulate is from "blowby." Blowby is when
combustion gases make it by the rings and into the crankcase. These gases
can get to the head by way of the oil return passages. A leakdown test
will show you if blowby is the cause rather than the valve guides. The
PCV system is supposed to take care of most of this pressure, but when it
becomes too great, it can't keep up.

On Mon, 23 Nov 1998 15:39:15 GMT ggthack@swansea.ac.uk (Graham Thackrah)
writes:
>I spent the yesterday swapping the head gasket on a friends 80 sport 
>as he has
>been suffering from what we thought was a dodgy one. Water behind the 
>oil
>is the pressure behind the oil filler cap is still there.
>
>Why?
>
>We thought of a poorly seated valve but wouldn't that just leak into 
>whatever
>port (inlet/exhaust)? Compression is nearly as good as new, high 170 

Adam Nelson '85 4000S, Blaupunkt cassette, Starbucks go cup, '69 Beetle,
1 piece
windows, hand held fan, '91 Vanagon, KYB Gas a Just, bug screens.
Columbus, Ohio
adamnelson@juno.com

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