How should the oil cap act with a good/bad AOS?
 

I just bought my 2000 S a few days ago and I get a small amount of oil smoke out the exhaust on a cold start. From reading around that might indicate a bad AOS and apparently it's possible to make a test by removing the oil cap with the motor running.

Does it make a difference whether the engine is cold/hot when I try this?

Second, what is supposed to happen if you have a good AOS and what happens if the AOS is bad?

forum search is your friend!!
 

You (after looking in search) will find that ALL flat six porsches will have a brief smoke upon start every once in a while. This is due to the design with these engines and as long as the amount of smoke is small, I don't worry about it...Now if the smoke bellows out for a longer period than just a few secs. or if it is a strange colour, like blue, then I would have it looked at.imho... and if this happens at rest, like at a stop light, then have it checked out also...

good luck....and remember, use that forum search!!!there are alot of VERY informed p-car owners on this forum...j.raby and others..... :D (plug) :D

As a new member, I have been using the search function extensively and combing though thread after thread to try and find some answers.

However, the limitation of one search every 30 seconds reduces its usefulness and effectiveness when you are unsure of the exact terms to search on.

But I am thankful to everyone who posts here. Its is a valuable resource and huge benefit to a new Boxster owner.

From what I understand, if your AOS is bad then it will be difficult to remove the oil cap due to excessive suction. I don't know if hot/cold makes a difference, but I would venture to guess that if your AOS is bad and you have thick smoke billowing out the pipe, it might not be a good idea to keep it running long enough to warm up. I also don't know what amount of suction, if any, would be considered normal, but perhaps someone else can answer that.

On a good AOS, you can loosen the oil cap and lift it up. On a bad one, like mine, I couldn't even loosen the cap. Also, if it's a total failure you will get lots of blue smoke. With lot's of oil moving into the combustion chamber you could damage the engine. When mine failed, the engine had a loud screeching like a belt tensioner going out when the engine warmed up. It was pulling air through the front crank seal.

Thanks for the informative reply (I've been searching AOS info on several sites). The second reason I think there might be an AOS problem is that the car has a stinky smell that I think is crankcase fumes (sort of smells like a pickup truck with a blown motor). The smell is most noticable near the rear fender vent on the passenger side.

Sometimes I'll do a google search which will bring me right back here to the forum.

Check for an oil or axle leak dripping down on the exhaust system. My 2000 S has a TIP. The passenger side of the TIP is the final drive side...my axle seal is leaking and I get that smell from fluid dripping down on the hot exhaust. I have an Indy fixing it early next year for about $300.

I just finished driving the car and checked the oil cap when I got home. There was no excessive vacuum, just a slight wet sucking sound so I guess my AOS is OK (for now).

The stinky smell very well could be trans fluid. There were recent repair receipts that came with the car. One of the repairs was for a leak repair to the trans axle seal. I'll check that out thoroughly when the garage gets a little warmer.

I did this same check at the dealer when I had my PPI performed. The cap lifted off with some small amount of suction. The tech said that some suction is normal and that the cap should come off fairly easily.