Crank case pressure???

radish · Mar 16, 2016

I've had my vege 1600 for 12-13 years and when I first got it oil sprayed out from the back of the pulley wheel, someone at vowo suggested putting a breather tower on which I did. So back then I vented the top of the rocker covers and problem solved.
But over the winter I decided that the empi bolt up rocker covers I had lying around should get used but I vented through the twin carb tops which I read was better way of venting? Now after a trip to ninove I now have oil spray in the engine bay coming from behind the pulley.
I know the easy answer is to swap it back but I need to understand why it's doing it and as I don't really do engines I'm lost.
Any ideas? I'd rather someone explain it as I switch off reading about engines!!
So why could it have to much pressure first off? And then why does it breathe better through the rockers?

Cheers Darius

Happystamps · Mar 17, 2016

You'll always have some pressure in the crankcase, because the piston rings only seal so well. You get a bit of what's called "blow-by". So your crankcase becomes pressurised like a compressor tank. Also, as your engine wears, the seal becomes worse, so you get more blow-by*.

This normally isn't an issue, because as stock you've got a breather, coming off your oil filler tower/generator stand, that allows that pressure out of the engine. (For legal reasons it cannot just be allowed to vent to atmosphere, which is what breather towers do- but whatever. It should go to a carb so that oily mist is sucked into the engine and burned)

The main issue with aftermarket breather parts is that they're too small in bore to allow all of this pressure to escape properly, so the pressure inside the engine builds up and finds a new way to escape- behind the pulley, in that little area of clearance where the crankshaft goes through the case.

So, your solution. You're using twin carbs, which is great for you but sort of a pain for this job. Nothing too hard though. Pick your favourite carb, and hook the air filter directly up to the stock oil breather on the oil filler. The advantage of using a carb is that it sucks a little bit, and gets rid of this pressure really well.
Try and avoid using aftermarket VW bits for your solution. For some reason they're only about 8mm diameter, whereas the original design was 13mm or 20mm, depending on year. How is that an upgrade? Beats me.

Anyway, what you're after is something like this:

http://www.bellflowsystems.co.uk/3-...ed above is neat, cheap, legal and effective.

radish · Mar 17, 2016

Thanks Happy
so what i have at the moment is a long winded version of what you are saying?

This isn't mine but is vent like this.
http://images.thesamba.com/vw/gallery/pix/652387.jpg" onclick="window.open(this.href);return false;

I have a compression tester so i will give a go as well, i've had it for years and never used it..

K@rlos · Mar 17, 2016

Do you still have a mechanical fuel pump? If not try a set up like mine...

Both rocker covers are vented too.

sparkywig · Mar 17, 2016

Darius, mine's vented to the carbs via a breather box.

radish · Mar 17, 2016

I'll get a photo tomorrow, but mine is vented to the carbs. I don't understand why it's started now when it was fine when vented to the rockers.unless my rings are worn as happy mentioned.
I do have an electric pump somewhere.

Cheers