Interpreting compression readings?

Car is 1988 VW Passat 1800cc with 'RP' engine; 185,000miles Problems; some grey smoke after crawling in traffic. a lot of oil seepage from valve cover gasket despite renewing it. (-the breather hose which leads to the intake has been changed-)

-otherwise car takes me up and down the motorway and round town in fine style.

cylinder 1: 9.8bar 'dry' 10.8bar 'wet'

cylinder 2: 10.5bar 'dry' 11.7bar 'wet'

cylinder 3: 10.0bar 'dry' 11.8bar 'wet'

cylinder 4: 9.9bar 'dry' 10.8bar 'wet'

The Haynes manual quotes values 'new' 9 - 12bar, 'minimum' 7bar, 'maximum difference between cylinders' 3.0bar

I wondered if the leaks past the valve stem oil seals could be pressurising the space under the valve cover? and would it be worth having them replaced. Any comments would be appreciated. Thanks

The readings are fine. The valve stem seals will only really let oil through, as they have only a little vaccuum on inlet side and tiny pressure on exhaust side. If you want to see how much and where the compression pressure is leaking then get a stup to pressurise each cylinder in turn and see where the pressure goes (by ear)

MrCheerful

YOu don't need to take the head off to change the valve stem oil seals but the leakage past the valve covers more likely down to that having been overtightened at some point, one of the few uses for some hylomar gasket sealant.

In article , Chris Holford writes Sorry about posting twice!

What to do about the smoke? There does seem to be some overpressure as I did fix the previous valve cover with gasket sealant and got oil blowing through the camshaft oil seal.

Ahh, fun & games time then, that's something blocked in the breather system or you've got a truly buggered engine & enjoy it while it lasts

Is there a horrible little oil strainer thing between the breather hose and the intake duct? Usually seems to be a stack of little metal plates with holes in them. Check that it isn't blocked with condensed oil vapour sludge. Presumably the pressure that's blowing oil through the camshaft seal is blowby past the piston rings that ought to find its way up the breather hose to be reburned.

James