Hi Doc:

That's an offer I can't refuse... an experienced 928-vac-leak doctor who makes house calls!

Should I buy some new vacuum hoses and connectors, just in case? Can I just pick those up at the local PepBoys or Kragen, or are these Porsche specific?

 

Vac hoses and conn are pretty generic, but that's almost never the fault. If the vac diaphrams aren't leaking (a big if), then the lines and connectors are next. We just gotta hunt it down the old fashion way. One of the local Porsche suppliers will have the vac pots if we need diaphrams(er, for the car I mean).

There's a spec for the vac supply somewhere in the WSM, but I can't recall where. I'll check it by touch, and then we can isolate back from the pots, to the mainfold, to the lines, to the source, etc.

Doc

 

Well, if you read the rest of this thread, you will see that I've tested most of this already. I am far enough along to know that the leakage is between the 4-way connector and the manifold at the electric solenoids. No need to reinvent the wheel.

 

Great news: Doc found two leaks that were relatively easy to fix - relatively meaning easier than replacing the black vacuum line...

Within minutes he tracked the leaks to two areas:

1. The male/male hard plastic vacuum connector that goes into the solenoid manifold did not seal properly on the manifold side. After replacing it with a thicker piece of vacuum line, the connection was tight.

2. The female rubber piece at the vacuum tank in the fender did not seal properly with the incoming vacuum line. After removing the tank and testing it for leaks, Doc found that pushing the line futher into the tank provided the desired seal.

We buttoned all up and went on a test drive. Ther was no flipping flopping of the flap anymore - all appeared to work as designed. I even think that my car now idles better than before! Hmmm... could it be that my mystery rough idle was caused by these vacuum leaks? I'll have to watch it for a while and see.

Well, Doc is my hero-of-the-day. Thank you, thank you, thank you!!!


Now the question is how long until the acutators will go out - they are getting proper vacuum for the first time in more than 5 years! Scary thoughts here...

 

Nicole
Did you pull the vacuum tank from inside the fender to test it?

 

Nicole:

Good work! That tank line wasn't leaking when we tested it a year or so ago. We didn't check the main mainfold source tube, so that was a good pick-up. Does the AT vacuum modulator line still have a slight leak? We left that alone because it was such a slow bleed down.

If this fixes the elusive rough idle, that is great news. My first thought all along was vacuum, but we never found a significant leak. Again, good work!

 

Yes, we removed the vacuum tank for testing, submerged it under water and pressurized it - no bubbles.

We did not touch the vacuum to the transmission - AFAIK that one is closer to the MAF, but doesn't affect the AC. Some day this one will get looked at, but since it has no negative effect on how the car runs, I don't see a reason to make it a high priority.

Well, next is the oil cooler...