m73m95

I have been driving my car for a week now since doing my head gasket, and it runs great. So today, I decided to give it a check up. I pulled the plugs, and noticed a little burnt oil on them, so I got a flashlight and there's oil on top of the pistons. Its not alot of oil, just a few drops in the valve reliefs. It doesn't smoke at all when driving, and the oil isn't low after a week of driving (almost 200 miles).

Where would this have come from? Its got new guides, and valve seals, so I don't think its from the head. Vacuum leak? Its got new AOS seals, and I've checked every hose I can lay my eyes on with the manifold on...

Also, my compression is a little over 120 in all 4 cylinders. (warm engine but the throttle was closed) and only has 67k miles (so I doubt rings....maybe though )

EDIT: 150 +/- on all cylinders with throttle open. I redid the compression test.

Any help?

Thanks for the help

FRporscheman

Isn't 120 kinda low?

white924s

depends on what the cranking speed was. I've always been told to look for consistency of numbers more than anything else. A leakdown test would be a better way to check for where the oil might be coming from. If you do the test and see any increase in crankcase pressure, then you'll know that you have worn piston rings (causing air to leak out of the combustion chamber in testing and oil to get sucked in during running)

m73m95

Could this be a vacuum leak? I'm still not totally clear on Porsche's whole AOS, IAC, vacuum system.....

I really don't think its a mechanical thing (rings, valve guides) just based on the miles, maint. records from the PO, and a redone head. The cylinders looked very clean, and absolutly no scoring on the walls. I'm not saying its NOT mechanical, I am just leaning towards the vacuum system.......if its possible that it COULD be the cause?

If this could be the cause, could someone explain how this system works...or point me to a link in the right direction?

Thanks!!

FRporscheman

How the AOS system works? It's simple. The crankcase is vented at the AOS connections, the AOS acts like a filter to keep the oil down and let the air up, then a hose connected to the intake sucks on the AOS housing, pulling the gases out. When the AOS is old and maybe broken, the hose starts sucking oil as well as air. Your AOS o-rings may be new, but maybe the AOS thing itself is internally broken or lost its ability to keep oil down? I don't know what goes on inside the AOS but there's no moving parts or anything.

Disconnect the AOS hose from the INTAKE side and see if it's got oil inside it. If it does, clean it and where it connects to, put it back on, go driving, then check it again. If there's more oil, you have your answer.

m73m95

Ok, simple enough...and I will do. Now, if this is the cause, I take it pellican or paragon, or the like will have new ones?


Thanks for the help

FRporscheman

You can check, but I don't think Paragon or vertex or whatever will have it. Pelican could get it for you. Try Sunset Imports (Porsche dealer in Oregon with the lowest dealer prices in the country). Or just buy a used one and hope it's better than your old one...

Jfrahm

I don't suppose it's overfilled with oil? Or was?

krystar

quick question about the AOS. is there supposed to be like a filter element inside there? cause i opened mine up yesterday...and it's just a empty cylinder

StoogeMoe

It's not likely to be your rings. There would have to be a whole lot of oil getting by to lay on top of your piston. Most of it would get burned off in a big cloud of blue smoke. Valve guides and seals could cause that but since you just had them replaced, it isn't very likely. If the oil is in all cylinders, then it is mostly likely coming from the intake. The AOS, as mentioned, is the most likely culprit. Check overfilling as mentioned also.

m73m95

I am going to check the AOS today. I agree that sounds like its the problem.

If I do need a new one, should I buy new, or would a used one be fine? (do they commonly go bad, or is mine the rare bad one .... so used should be fine, cause they don't usually wear out)

FRporscheman

The AOS usually does not go bad but it does happen. Get quotes for a new one and a used one.

I just noticed the new compression test numbers - that looks much better! And it makes rings much less likely.

m73m95

Sunset has the AOS for 135 = not to bad.
But if they don't go bad regularly then I'm sure someone parting out would have it MUCH cheaper than that.

Thanks for the help everyone!! Love this site

Dmitry S.

Check this first.

m73m95

ok...well, when I got the car from the PO, it had a blown head gasket, and bad oil cooler seals. IE: when I drained the crankcase it had over 2 1/2 gallons of a nice oil/water mix.....so, yeah, it was over full. There was oil in the entire intake system....a good half cup in the air filter housing.

I cleaned everything out that I could get to. And I tried to flush out my AOS with simple green as best I could. I thought I had gotten it all cleaned up. There is no more oil in the air filter housing, or my AFM.

Didn't mean to keep anything out, from the story.....just thought this was something seperate.

Does this mean my AOS is still bad? or.....well, ok.....YES!! I guess at one point the crankcase was way over full ..... now what? More cleaning? Will it eventually work its way out?