Subject: Vacuum, and how it sucks.
From: "Ed Ruiz" <eds928s@erols.com>
Date: Fri, 11 Jun 1999 7:58:52
X-Message-Number: 18

Dear fellow sharksters:
First of all, you can all thank (or blame) Roy V. for this post. He knows 
how to prod me into writing these sort of messages.

So you suspect you have one or more vacuum leaks. Based on my limited 928 
experience, you are probably correct. Since different MY 928s have 
different vacuum lines and/or are routed differently, I will only talk 
about the system in general.

Your should have a line diagram of the emission control system on a large 
silver decal located on the underside of the engine hood (bonnet). Most of 
the vacuum lines can be located using the diagram.

To check the system's integrity, you will need a vacuum tester (Myti-Vac).
Each line to be checkd should be isolated.

1) Inspect all lines and connections. I have seen rubber connectors that 
have swelled and no longer make a tight fit.
2) Inspect the large oil return lines on the right cam tower (the left side 
of the engine as seen while standing in front of the car).
3) Inspect the oil filler "O" ring and the dip stick "O" ring. 
4) Inspect the large oil lines to the filler and the plenum from the 
throttle body.
5a) For pre-87 928s, check the two large "O" rings at the base of the 
Mass-flow sensor. While that sensor is out, check the vacuum manifold that 
looks like a spider and all hoses adjacent to the throttle body that are 
now accessible. Also, check the rubber connectors between the intake plena, 
and the throttle body.
5b) For 87 to 95 928s, inspect the rubber boot the mass flow sensor fits 
into. (Since the area under the intake manifold is inaccessible without 
removal or the manifold, all you can do is hope all is well down there.)
6) Inspect the check valve that comes off the brake booster vacuum line.
7) Inspect the "T" or "X" connector below the check valve. One of the lines 
here goes to the AC/Heater control unit. (Be ready vacuum leaks here.)
8) Inspect the "Y" fitting that connects to that connector. These lines go 
to the cruise control and the vacuum reservoir.
9) If your 928 is an AT, check the line to the transmission.

My experience has found that items 2, 4, 5a, 7, and 8 have been areas where 
I have seen most of the vacuum related leaks.

I may have missed some items, but I hope you get my drift. I think there 
are procedures for finding and repairing vacuum leaks at Greg Nichols web 
site.

I hope this information helps. Merry motoring, Ed.
(Roy, after the Frenzy, you owe me a cold one.)