Brake servo dismantling.

[Doctordiesel77]

I have never come across a servo that had failed other than through rust holes in the casing, but thought I'd see how they come to bits in case I ever do have a dud with a good casing and a good one with a rotten casing. The casing just unclips by straightening the metal retainers (on this one they'd mostly rusted off!) and removing the master cylinder, it may need levering apart using plastic trim removal tools to avoid damaging the diaphragm. The two washers on the end of the rubber bellows over the through bolts are loose, lift these off, then twist and ease the bellows over the lip on the bolts. The plastic valve assembly should now push out from the other side, with the diaphragm still attached. The rubber diaphragm can then be removed, leaving the valve & pushrod assembly attached to the metal diaphragm support.

[Jeff Turbo]

Nicely done Mr Guru. I took one apart a long time ago to find out if they can be fixed but couldn't get any parts for it at the time

[Doctordiesel77]

The master cylinder pushrod just pulled out over the plastic lip and the valve assembly pushed out of the steel diaphragm, it seems to be crimped into this, so might be best left in one piece if you were reusing it and both parts were ok. If I had to reassemble them I'd be tempted to add a very thin layer of tiger seal or sikaflex to make sure there were no leaks. I took the thin metal retaining ring out of the pedal side at this point, then the rubber seal and plastic ring out of the cylinder side.

[Doctordiesel77]

The only thing I could see that seemed to be holding the piston in was a centre punched washer on the cylinder end of the pushrod. As the servo was scrap anyway I punched this out to see what would happen & it came out without any collateral damage. The pedal pushrod, spring and valve came out in one piece, there is a ball joint on the end, seals didn't seem to fit over this, so I tried to take it to bits, this destroyed it. My next experiment is to see if the other end comes to bits, but it looks as though freeing a sticky valve or replacing a diaphragm are possible repairs, whereas replacing seals in the valve aren't.

[Doctordiesel77]

Nicely done Mr Guru. I took one apart a long time ago to find out if they can be fixed but couldn't get any parts for it at the time

I suspect that parts will still be unobtainable, especially the parts that rust away! I might have known that a genuine guru would have done the job already