overlooked vacuum leak sources

[mallard ducks]

I've been replacing all vacuum lines, hoses, fittings, boots, intake manifold gasket, etc. on my 944S

Everything's done but I still have a decent vacuum leak (exactly the same as before doing everything - no improvement, no worse)

The only thing left that I can think of is the fitting in the plastic intake pipe for the AOS breather hose has cracked all around its base where it mates with the pipe.

I would have replaced everything else anyway, just as general maintenance on a 21-year old car, but my experience may save someone else a lot of aggravation...

...don't forget about checking for cracking/seperation of those hose fittings on the plastic intake pipe.

[krystar]

have the engine running and take carb cleaner and spritz it in potential leak spots. if the engine revs up, u found yer leak.

[Techno Duck]

Check the throttle body as well. Lots of O-rings on it that shrink / go bad.

[mallard ducks]

throttle body o-ring already replaced - everything's been replaced (what a PITA on an S) and neither I nor anyone else can find the leak - except at this hose fitting

It's easy enough to miss because you wouldn't necessarily ever assume it would crack and you wouldn't necessarily be spritzing at that spot either. I only caught it by chance when I took the plastic pipe out to get at the TPS. It was when I decided to give the pipe a clean that I saw it.

I just got a new (used) plastic pipe off Ebay. The fittings are good, so this weekend I'm looking forward to vacuum leak free driving!

[Pops944]

Another way to locate a vacuum leak is to leave the engine off and pull one of the end point vacuum lines. Hook up an air tank set to about 10 # pressure to the pulled vacuum line. Then, in a relatively quiet area, listen for the air leak. Once you have a "vicinity" for the sound spray a soap mixture on the suspected area and look for bubbles. This method saves gas and the engine is cool to work on to repair the leak once found. Works great; I found two major leaks and several small ones this way.

[earlr85944]

that sounds good!