HELP!!!! How do I re-install cupped "o" ring

[tank1949]

Trying to eliminate any possible reasons why my disk brakes failed prematurely, I took a fellow forum member's advice and examined my master cylinder's insides for a valve required for drum brakes but not disk brakes. I was hoping that the manufacture had mislabeled the packaging. Yet, mine didn't have the valve. Good thing, but now more problems. I can't collapse the cupped "O" ring that fits in a machined grove so that I can push piston back into MC. If I had a device similar to a piston ring installer, that would be great, but I don't believe that there are any tools that small. Attached are photos of my dilemma. Any suggestions on squeezing the "O" ring down to fit inside grove and still ride on the piston would be appreciated. The "O" ring keeps popping out of grove as it is expected to provide good sealing. See attached photos.

 

[Grub54891]

Re: HELP!!!! How do I re-install cupped "o" ring

I guess you could cut some thin plastic,like a thin milk jug,or something thin like that,wrap it around with a hose clamp. Leave the plastic long enough to reach inside the mc a bit so ya can get it past the snap ring groove. Hope ya get it together.
Grub

 

[Tnstratofam]

Re: HELP!!!! How do I re-install cupped "o" ring

This is just a shot in the dark, but try putting the piston with the o ring on it in the freezer for a few minutes. then try and install it. You could also try some petroleum jelly on the o ring. Good Luck...

 

[smokeonthewater]

Re: HELP!!!! How do I re-install cupped "o" ring

don't use petroleum jelly... lube with ONLY brake fluid

could you insert the seal into the bore first and then push the piston into it?

 

[phillyg]

Re: HELP!!!! How do I re-install cupped "o" ring

Buy a stainless steel hose clamp slightly larger than the o-ring, smear it with brake fluid, tighten it down just enough (but not too much) to allow the cupped edge to slip inside the cylinder bore, and loosen the clamp as you push in on the piston.

 

[GA_Boater]

Re: HELP!!!! How do I re-install cupped "o" ring

Those are a pain in the you know what. I've used some aluminum flashing making sure there are no burrs (don't want to cut the seal), fit inside the bore and lubed with brake fluid only, then push/force the piston into the bore. The milk jug plastic might work, just not sure if it ends up being too thick. And wrapping the shim material around the piston with a hose clamp might be possible, just don't tighten too much.

I wouldn't use a hose clamp with no shim. Too much of a chance cutting the seal. Also be ready for the whole thing to come out of the bore because of the spring. It will be tricky, but not impossible to do. Good luck.

 

[Tnstratofam]

Re: HELP!!!! How do I re-install cupped "o" ring

Smoke is right don't use petroleum jelly. I wasn't thinking as the admiral says.. Forgot what you are working on. Brake fluid only... Sorry

 

[tank1949]

Re: HELP!!!! How do I re-install cupped "o" ring

Thx to all. Got of phone with Titan who made MC. They are sending me new cups. Cannot use std part's cleaner to clean out MC. If you do, solution expands live rubber. I didn't know?????? Only lub to use is brake fluid and clean with alchol only. Hum???????