Exhaust fumes from oil filler cap

Title says it all really...if I take the oil filler cap off when the engine is running there is some pressure there and some exhaust fumes too. Not a lot, but some.

What does this mean please?

Also, out today between the showers it lost power going uphill, and eventually stalled. It re-started again, and missed for a little distance, then was fine. Any ideas? Related?

Thanks

head gasket knackered....

Originally Posted by Malfa

Title says it all really...if I take the oil filler cap off when the engine is running there is some pressure there and some exhaust fumes too. Not a lot, but some.

What does this mean please?

Also, out today between the showers it lost power going uphill, and eventually stalled. It re-started again, and missed for a little distance, then was fine. Any ideas? Related?

Thanks

Can you give us a little more to go on?
* Does it foul its plugs?
* Is there an emulsion of oil and water (mayonaise type stuff) on the dipstick or oil cap. (or the rad cap)?
* Has this only happened once or is it a regular thing?
* Could it just be a miss-fire due to a bit of damp as you say it was between showers?
* Are the plugs, leads, cap and rotor arm in good order?

Don't forget , the fumes could just be a bit of general wear and tear (ring's/valve-gear) that may well have gone un-noticed for years if this stall/miss-fire had not happened. Before condeming the engine in any other way get it compression tested and the valve clearances checked. Mine ran uneavenly when I first bought it, a compression test gave uneaven results, after re-shimming the valve clearances, an oil change, and a good run/thrash up the M6 all is well in the compression department.

You should check out the AROC forum.
There's a bloke with a S3 Spider with exactly the same problem!
Chris

Check your breather is clear. On a carb engine it's at the front carb side of the cam covers. There are always fumes and pressure coming from a running engine, but it should be able to find it's way out through the breather!

Plugs are fine - no fouling.

Water is clear - no mayonnaise and it has plenty of grunt normally.

It has only happened once and it did clear up quick and run normally afterwards.

I'll check the breather - it's the fumes I worry about most.

Thanks

Which series/year spider is this?

Series 3, 1985 or 6

Originally Posted by Malfa

Series 3, 1985 or 6

As you remove the oil filler cap you say there is ‘some pressure there’. This is nothing to worry about provided it is not excessive. If you start up the car and switch off after a couple of minutes and remove the oil filler cap you will see ‘some’ fumes. Again provided this is not excessive it’s not unusual. As per RICKSALFA post, check the engine breather hoses. I am not sure if this applies to the S3, but if it has an oil vapour separator (as in the S4) remove it, and flush it through to make sure it’s not blocked.
The symptoms you describe can also occur if you over fill the oil.
Out of interest, why did you remove the cap with the engine running in the first place? Were there some other symptoms that made you do that?

As far as the stall and misfire are concerned I feel this is a simple case of dampness around the electrics…(it has been a little on the damp side recently!!!). Give it a good spray with the WD40, that should sort it. Better still, when the sun finally comes out take it for a good long blast!

Fumes almost certainly due to general wear. If plugs not black and all 4 are much the same colour then I wouldn't worry about that but do check for blocked breather. Old engines usually have huge amounts of sludge around, often due to lack of oil changes. Going limp on a hill?? I'd suspect fuel starvation due to muck swilling around in the tank, carbs and lines. On older cars, especially with steel fuel tanks, this is pretty common. (I don't know for sure what type of tank yours has).

Hello 'agin Wrenched: Good Hols? What he said, piston ring blow-by, general wear and tear?:

I did have a good time thanks ZF. Looking for the next opportunity though, bit too short. Still, had a lovely-but-wet day at Brooklands on Sat for the reunion.
Meant to mention on the subject of compression loss/blow-by/crankcase fumes, that compression tests, hot and cold, would put to bed any concern over bore and ring wear.

Glad you enjoyed it mate, and welcome back to the Rat Pack: