careful1

I've checked the vacuum to the module and found that I have none. Neither at the module or the line going to it. What is the part # of the module and how do you take it out. Thanks Doug.

Maleficio

I'd try to figure out the lack of vacuum before changing the module.

JHowell37

Then your problem is either in the flexible line that goes from the back of the engine down to the steel line that runs along the top of the torque tube, or the flexible line from the back of the torque tube to the modulator.

careful1

Guys , I've tested the vacuum with a mighty vac from behind the manifold and have no vacuum. Then I tested the module and still no vacuum.Then I plugged the vacuum line ahead of the module... no vacuum. My conclusion is multiple vacuum failure. The top of the module is cracked. Thanks ,Doug

JHowell37

So replace what's cheapest first, which would be the flexible vacuum lines.

What year?

careful1

It's a 1988.

Maleficio

RTV.

Jascd

just to be clear, you would have to have a major sort of leak to have no vacuum at the splitter at the rear of the engine (not sure if that what you mean when you refer to the manifold). Check that the source from the throttle body is producing vacuum with the car running. Be careful that you don't pull it off the throttle body though!

Then if that's OK, check the splitter is not split... then trace and test each of the other lines. Leaks on the fuel damper circuit are not uncommon. Once you have done that make sure the line to the transmission is Ok by plugging it at the transmission in then mityvacing it at the splitter and then a further check with it connected at the splitter and with the mityvac at the transmission end. You should be getting around 17 inches of mercury of throttle vacuum at idle (at leas that's what my s4 produces and I have no leaks).

The vacuum modulator on the transmission should hold vacuum from the mityvac for a long time, 5-10 minutes (i test with 25-30 inches)

good luck

Landseer

I read here somewhere about the metal line leading from the splitter and down along the torque tube can become squeezed closed, especially during service like motor mounts if somebody was overzealous in lifting the engine. More likely the flex pieces as mentioned already by J.

Some people have been known to run an additional heavy-walled rubber vac tubing and tucked it up, zipped to the torque tube, the purpose being to simply bypass the somewhat-difficult-to-remove hardline.

joejoe

On my '86.5 I found the leak for my line was the rubber hose just after the hard plastic one coming from vacuum spider. It is a real bear to get to due to its' location. Cracked mdulator does not sound good though.

WallyP

"What we have here is a failure to communicate." After reading the original question a few times, I think that Doug is correct.

"Guys , I've tested the vacuum with a mighty vac from behind the manifold and have no vacuum. Then I tested the module and still no vacuum.Then I plugged the vacuum line ahead of the module... no vacuum. My conclusion is multiple vacuum failure. The top of the module is cracked. Thanks ,Doug "

I think what Doug is saying is that he attached his MityVac to the transmission line at the rear of the engine, and could not pump up any vacuum. He then went to the modulator and attached the MityVac, and could not pump up any vacuum, probably due to a cracked top. He then plugged the line on one end and attached the MityVac to the other end, and could not pump up any vacuum.

So, if that is correct, I agree with Doug - he has a bad modulator and a failed vacuum line.

careful1

Thanks Wally, That's exactly what I was saying. Is it difficult to change out the module or do you just repair the old one? Doug

WallyP

I don't think that there are any user-repairable parts in the modulator...

Replace it, get the vacuum line fixed, and adjust the modulator. It would help if you can rig a pressure gauge for the adjustment, but you can eventually get it close to right by repetitive adjustment/driving/adjustment.

careful1

Thanks Wally, I just ordered the parts from your store. Thanks ,as always , for your insight. Doug.