Blowby crankcase pressure issue.

Got what I would consider excessive blowby on my ‘84 8V GTI (EV Eng code). Has a whisker over 131k on the clock and with motor running if I take the oil cap off there’s significant blowby escaping. Not enough to blow the cap off if just rested in place, but makes it dance alright. There’s no PCV in my system which checking on ETKA is correct. Thing is that when I uncouple the rigid plastic hose coming out of the rubber bung on the cam cover going to the airbox there is very little blowby gases looking to escape making it look like the mesh filter on the underside of the cam cover is blocked, which it isn’t I’ve checked. Also, no blockages after that to point where I’m checking the escape at end of rigid hose. Am I missing something here like with having oil cap off air is being sucked in and same air then blown out? Compression check revealed better than expected results from Bentley manual but has had a head skim recently. Just looking to resolve cos I understand excessive crankcase pressure can cause problems. Thanks. In the photo attached it’s after undoing the blue circled jubilee clip where I expect to find the gases escaping.

 

How much oil does it use?

 

It’s not too bad, 10/40 about half a litre per 1000 miles. Last drop I’ve changed the oil to 15/40 to see if that makes a difference. Number 3 plug does oil up fairly quickly though.

 

That's quite excessive tbh.
Was it parked up unused for a long time?

 

It was. I parked it up for a couple of years for one. I think before acquiring it from a middle man it may have been parked up for even longer, barn find type scenario I feel. Does that make a difference?

 

I wonder if there's a stuck ring or 2.

 

Ah, possibly! Is there anyway to check this without removing pistons? And if I continue to run the engine can this cause damage please?

 

Not really tbh, you could get a leak down test done.

 

Yeah, they’re not expensive at all on eBay (so long as they work) and I’ve got a compressor so I’ve ordered one. I’ll post the results hopefully in a few days. Thanks.

 

Keep us posted!

 

Leak down test is for low compression test, if it uses oil can be either valve stem seals or piston rings. And from all piston rings only one responsible is the oil control ring, witch gets plugged/stuck with burnt old oil.
About any car new or old can make the oil cap dance if loosened. Even my newly built engine with new oversize pistons used 1l in about 2000 km, though i beat on it hard to redline.

 

Was going to post this.