And what else can go wrong?

[magpies]

Purchased this a little while ago, it looked in very good condition but had a some gasket goo around the mounting stud area.

The car has been in the garage all of the time and when I hooked up the vacuum line there was a hiss. I tried to chase the source and while investigating I found the hiss stopped when I pressed the brake pedal! We performed a smoke test and the footwell filled with smoke. So set out to dismantle the servo and found I could only undo 3 nuts, the other just turned (it did loosen 3 or 4 turns first). I then had to cut the stud - thankfully the 3 or 4 turns allowed an air hacksaw in.

The failed stud is obvious

[mk1fan]

Hans can help.

[v8s4me]

I have one you could borrow but it will need modifying because the rod is too long. Let me know tonight if you want it sent up and I'll post it tomorrow.

[phillpot]

Get the welder out

[greymrj]

Philpott has a point. If the servo is otherwise sound then VERY careful use of a MIG, on the lowest power consistent with a good weld, and a wet cooling rag might well work. make up a new stud out of a bolt, tack the bolt head to a thin washer. Make up a simply wood jig to get the studs in line until it is tacked in.
Make sure to keep the inside of the servo clean and work with the servo bulkhead face slightly down so the risk of damaging the diaphragm is as small as possible. The vacuum pipe opening to the servo must be left open so any change in air pressure as the air heats can deflect the diaphragm. I think it is very well worth a try on this side of the diaphragm.

Hang on though! If the smoke test on the outside of the diaphragm led to smoke coming to the inside of the diaphragm, doesnt that mean the diaphragm has failed anyway?

[phillpot]

greymrj said:

Hang on though! If the smoke test on the outside of the diaphragm led to smoke coming to the inside of the diaphragm, doesnt that mean the diaphragm has failed anyway?

Both sides of diaphragm are under vacuum at "rest"............... clicky




Some careful welding, bit at a time, lots of wet rags for cooling, sorted in no time!

If you get a pin hole or two I'd even go for patching over with "chemical metal" or similar rather than getting things hot again re-welding. Pressure is from the outside pushing the "filler" in unlike trying to patch say a header tank where pressure is inside trying to blow the patch off?

[greymrj]

Ah yes Mike, you are right, I read it again and spotted 'hissing stopped when brake applied'. So diaphragm probably OK. Out with the MIG!