jserio

I can't find it in the WSM. Can someone hook me up on an 87 S4?

jserio

This really f*cking blows. While probing around for leaks ( which I found many of) I broke the stem off the junction that is in the brake booster. I'm sure a few of you know what I mean.

The first picture shows the car running giving about 20 lb of suction. I do not know what it should be giving. THe picture is also showing the stem I just broke.

The second picture show no vacuum at the cross junction. Futher checking this the black line that goes into the firewall is good. Held 15 lb no problem. The white line that goes to the front of the engine is good. Held 15 lb no problem. The line that I assume goes to the cruise control nada. No good. Now that line goes into a 2 line fork. A black hose and a white hose. Black is good white is bad.

Now where the black hose goes into the firewall there is a white hose next to it that goes to the heater valve. There is no vacuum there. I know I will have to go in behind the consol for those. If someone have a pic of what it looks like in there I would be obliged.

I stopped there cause I couldn't take anymore. How difficult is it getting to where those lines that go to the cc? If that's where they go.

It is now no wonder why the heat is not working and the cc is not working and hell know what else.

macreel

Joe... In the WSM, p. 87-2, is a vacuum layout for A/C-
is that any help??

(BTW your gage appears to read 20 inHg not PSI -
at idle that's ~normal)

G'luck.

WallyP

I got a bit confused on the black and white lines, but...

There should be a line that runs to the driver's fender, behind the wheel. This line supplies the vacuum reservoir and the cruise control servo (tempostat). It should hold vacuum, but if you are pumping it with a MityVac or similar, it takes a LOT of pumping, as you are emptying a vacuum reservoir.

The black line that runs into the firewall supplies the HVAC system, which is where most of the leaks live.

Pull the small carpeted panel from the driver's side of the console. Look by where your right calf would be, and find a bundle of small colored plastic vacuum lines. Get a few inches of rubber tubing that is a tight fit on the lines.

Cut the orange line with a sharp razor knife. Use the vacuum tester to pump down the end that runs up into the dash - not the end that runs forward to the vacuum solenoids behind the radio. The dash end should hold vacuum. If it does, splice it back together with the rubber tubing. If it doesn't (and I'll bet that it won't), use the rubber tubing and a plug of some sort (golf tee) to plug the end that goes forward to the vacuum solenoids. This will stop the leak until you can get around to replacing the central vent vacuum actuator.

Repeat on the blue, green and yellow lines if necessary.

The black line is the supply. The white line goes to the heater control valve, and if it leaks, you want to install a new one.

shaaark89

joe,
i may have that part in my spares.



20 is good. my car makes 17 at idle with no vacuum leaks.



the black goes to the climate control as wally said. it feeds into the row of solenoids so each branch off those must be checked as wally described.
the white line goes to the flappy. follow it to the front of the motor and you will find a solenoid that it connects to. coming out the other end of the solenoid is a line that goes under the intakwe to the flappy. that should be checked as well to be sure the flappy actuator holds vacuum.
the forks in the line that goes through the fender wall should be checked individually. one goes to cruise, the other to the vacuum reservoir. as wally said, you may have to pump the reservoir one for a bit to build up vacuum.



the ones that go to the cc are accessable by removing the wheel and fender liner.

there is also a second vacuum system that originates off the top of the throttle body under the intake. it exits behind the motor around the mass air and goes to a 5 way splitter. one line to the fuel pressure regulator, one to each fuel damper and one to the trans vacuum modulator. should check these as well. will mostly affect the trans if leaking, but also can affect the fuel delivery some.

jserio

With the 2 lines that go into the fender, Do you know what color goes to the vacuum reservoir? How how many pumps should it take. Cause I only pump maybe 4 times and there was nothing. I'm going to try that one again. I have a function this evening but I am going to continue tomorrow. Thanks for some great info Wally but I am sure I'm not quite done with you yet

Mac, I was looking at the a/c part and it didn't seem to informative for what I was looking for. Wally should write a repair manual. I'd buy it .

jserio

You were right Wally. It took like 12 pumps but it held vauum on those 2 lines into the fender with no problem. With my cc not working what line do I test inside the car or is it one of those at that little junction were your right calf would be. Would be sweet if I can come out of this with my heater temp and cc working.

WallyP

Normally, if you fix the HVAC vacuum leaks, the cruise control will work.

jserio

I will print this up and get on it early. These cars you always to remove stuff just to remove stuff to get at a problem.

Thanks Tom. This will be fun. I will be at 928 on Monday so I will get one while I'm there. I hope my jury rigging holds up until then.

jserio

Ok, further into this mess I went under the dash/consol and the junction was right there. (SIDE NOTE: removing the steering wheel give you way better access to this area.). The orange one leaks, the blue one leaks, and the yellow one leaks. The white one is fine as I just replaced the heater valve. The black one is okay. I tested all the lines to where they head up into the dash. I tested none that go to the solinoid. I have included a pic so people can see what it looks like in there that have not had to delve in there yet. What to freakin do from here.

jserio

Got a nice cut from the razor slicing the yellow and blue lines. Now before I continue I want to say that the piece I broke (read above) the little vacuum hose was not attached while test. I only figured this out late in the day. Would that have effected the test on those lines inside the car? I would also like to know where the yellow, black, and blue hoses go to. I know the orange and white already. And speaking of the orange, I am very very afraid to ask but what will it take to fix that problem?

Ed Scherer

Joe,

You might want to read through the following:

• John Pirtle's excellent "928 S4 Service -- Vacuum Actuators" write-up
• The thread "Need help replacing vacuum actuator"
• The various Climate Control tips on Greg Nichols 928 Tips website

heinrich

Joe there is a vac diagram under the hood IIRC ..... when you're done wiping the blood from the lines, you'll need to delve deep into the dash. It gets funner from there (is that a word?) That broken piece ..... btdt, said the same swearwords. ..... it's far less bad than it seems. Glue the bastard back on or get a new one ... cost not much at all. The whole plastic shebang comes out of the Spaceship Enterprise-looking metal unit.

jserio

Thanks Ed,Heinrich.

That's funny Heinrich. I was lucky I had some towels handy or I would have been spending the other portion of my evening scrubbing the floormat.

I am still very scetchy on the vacuum stuff. I am going to read through Pirtles again and see if I can recruit some talent on this one. I will update my progress.

WallyP

Black - Source.
White - Heater Valve. Pull air cleaner to replace.
Blue - Inlet Air Flap (recirculate/fresh air) Pull blower to replace.
Green - Defroster Flap. Pull console to replace.
Yellow - Footwell Flap. Easy to replace.
Orange - Center Outlet Flap. Pull console to replace.