RallyCV

Go figure, a 19 year old plastic vacuum actuator will only stand up to one winter of Wisconsin hooliganry and road salt. I found the blue line snapped off of its nipple over the weekend.

Anyone know where I can find a new one? I have access to a couple of 100Qs at the local salvage yard, do they use the same part?

AV8RUK

easy to fix, impossible to replace as they are no longer made. The fix is also quite strong, and I have done this many times on 2 of my quattros, 2 other quattros, and also several other vacuum operated units on other cars, such as cruise control units etc. the plastics get brittle over the years. Vacuum units on audi transmissions get overlooked when clutches and bushes are done, and usually suffer.

you need 3/16inch brake pipe, like cunifer. copper pipe is ok. In the UK i found some normal copper pipe from a hardware store was a little narrow. About an inch and half long, max.

cut the broken stub so it is smooth. Makes for easier working
drill out with a suitable drill bit, slightly larger than the pipe stub that you will insert, so that a decent length of pipe can be inserted.
Use thread lock or bearing fit/retainer loctite to keep the new copper stub in place.

The longest part of this job is getting the white plastic vacuum unit off (audi call it a manifold in their parts list)
cutting the pipe, drilling the counterbore to fit it, and loctiting the stub in will take you about 15minutes, tops.

photo guidance- this is the vacuum operated cruise control for my GTO, and next to it is the difflock that I repaired in similar manner



Hopefully this is useful

AV8RUK

Sorry, forgot to answer the other part of your post. the same module is common across all the audis with lockable diffs. 857711995A, also known as throttle control element in some parts catalogues. This number appears in quattro and 100q 200q parts lists.
If they are available in the scrap yard, grab them. I would suggest that the repair also be used. The internal diaphragm is subject to perishing, and is much harder to repair, as any effort to glue a rubber patch makes them very stiff internally.

RallyCV

I'm glad you mentioned the part number, I found this little gem on the 4000 forum. A late Mercedes W123 door lock actuator should do the trick.

http://search.audiworld.com/showthread.php?t=2224062

http://mercedessource.com/node/1286

RallyCV

The Benz part works perfectly but it takes a little effort to get it installed. Some precision machining (i.e. dynafile) was required to turn down the end of the shaft to accept the die, and only 2 of the three mounting holes line up, not bad according to Meatloaf's standards.

90q UK and ROI

if it's only the bellows on the shaft and especially if the collar on the shaft end is intact, I have just repaired mine with a wrap of loom tape (rubberised and sticks to itself) and some small zip ties : )

90q UK and ROI

if it's only the perished bellows on the acctuator shaft/rod losing vacuum (won't engage) and especially if the collar on the shaft end is intact, I have just repaired mine with a wrap of loom tape (rubberised and sticks to itself) and some small zip ties, you have to leave the tape over-long and baggy so it can concertina in and out with the rod : )

RallyCV

FYI - Three years on and the Benz part is still going strong.

90q UK and ROI

BOSCH part no. 3 340 522 025 is more or less a straight replacement with a little trimming