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MG TD TF 1500 - Rear Wheel Cylinder Kit

Things seemed to be going smoothly with the rear brake refurbishing. And then came the kick-in-the-pants that can take one down a notch quite easily. I can't figure out how to install a rear wheel cylinder rebuild kit. The question is about the 'washer' that comes in the kit. It's not an 'o-ring', it's square in cross-section, not round. It's shown in the attached image. I don't know where it goes. There are two possibles, as I see it.-- one is to put it into the groove on the free floating piston - the other is to put it into the groove on the piston that's attached to the dust cover. If I put it into the groove on the free floating piston it seems virtually impossible to insert the piston into the cylinder. No problem with the other piston. Looking at the physics of the wheel cylinder I can't imagine why there would be a sealing component on the free piston The slot for the handbrake lever messes that up. Can anybody confirm my idea that the washer goes on the fixed piston? Thanks -- stupidly, Bud

Bud Krueger (TD10855)

Hi Bud, when I rebuilt my cylinders I put the sqaure section o-ring on the outer piston. I think the intention must be to act as dust seal (although there does not appear to an equivalent seal on the front wheel cylinders). Matt
Matt Davis

Hello Bud, I just dug some old cylinders out of the attic. Two likely late-1980s Lockheed cylinders have the rubber in the outer piston groove. I removed one, and it is a thin, flat square-shouldered o-ring. The ones in my older spare Moss rebuild kit are also flat/thin/with square edges. I dimmly recall the original cylinders didn't have this outer seal, so I don't think it is really needed. You could probaly go to a parts store and try some differet o-rings that would fit and work better, if nothing else to keep the groove from filling up with gunk. George
George Butz

Thanks folks. It only makes sense for the square o-ring to go into the outer piston. The floating piston has the groove in it for the parking brake lever. The washer would get in the way. Try as I may I was not able to find a decent parts diagram showing all of the components in the rear wheel cylinder. Bud
Bud Krueger (TD10855)

Bud,
When I rebuild these, I coat the metal piston with never seize before I put the pin back in. This, with silicone fluid make them (and the handbrake) last forever, no worries. Just a thought.
-David
D. Sander

Bud - like with many repair kits, that flat washer (I can't call it an 'O' ring may not be used on the cylinder you have. It could be for another, similar, but slightly different cylinder. My approach would be to leave it out since neither grove seems to be suited for it. Cheers - Dave
David DuBois

This thread was discussed between 02/08/2011 and 03/08/2011

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