After getting some vacuum pots and elbow's from Tom Falkenburg, ( Thanks Tom! )and the weather finally co-operating, I borrowed a mity-vac from a friend, and tackled the vacuum leaks. R&R the heater core pot, and the floorwell flap pot, replaced a hardened elbow at the gate switch, for the flappy, and I still have a leak, yes, MUCH slower than before.
Start vacuuming the individual lines from the 4-way. Hmmm, the vacuum reservoir is TIGHT! The line going to the flappy switch has an extremely small s-l-o-w leak, no problem there, and the HVAC line seems to be as good.
Well, lets check out the 4-way. Someone told me to twist the rubber lines off the 4-way.......OH S&%$!!!!!!!! THE 4-WAY IS A MOLDED ITEM!!!!!!! Now, where am I going to find one of these??!???!!?

Off to the parts store I go....Buy two 3-way splitters, come home, and cut 5 little vacuum lines, and plug everything together. Start the engine up, allow time for vacuum to get accumulated, actuate the controls, everything seems to be working. Pulled the pot to the floorwell apart, and yeah, there is a small visible hole (This was the largest vacuum loser)
Check in with Zandramus, yep, he's gonna be home, go check out the Yellow 928, and while driving home, try the cruise control, and IT WORKS!!!!!!!!! First time since we've owned the car!!!!!!! <img border="0" alt="[burnout]" title="" src="graemlins/burnout.gif" />

 

I found and fixed a couple of vacuum leaks on my car also. My cruise control still doesn't hold. It slowly decreases speed. I still have a leak somewhere. Can you give me more details on how you fixed yours? Were is this 4-way you are talking about? Any info would be appreciated!

 

Hi Charles,
The 4-way splitter is after the check valve, right after the vacuum take-off on the brake booster, under the hood, against the firewall, driver's side. If you still have the blue colored check valve, your splitter should be just after it. At least, my check valve is blue.....
Best thing to do, is to borrow or buy a Mity-vac tool, and start isolating each vacuum line, and test each one. You may even find the cruise control leaking? Mine also drops about 3 to 5 mile-per-hour, after I've set it, but then stays there.
Wally told us at SITM, many of the HVAC vacuum pots, at this age, leak, even the distributor block can leak. Lines are exposed to chaffing, getting bent, or smashed. Isolation of each line and system can be your key to finding the true problem, or all of them.
I found a few of the line connectors to be hard, and needing to be replaced. Turns out this same problem happened to my splitter! The rubber wasn't "clasping" the lines well enough.
It's best to remove the air filter housing, to better see and access the vacuum lines.