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MG MGA - Rear brake fluid leakage

I have recently resealed a rear brake cylinder due to a slight leak evident as a drop of fluid on the base of the backplate and light contamination of the shoes. Despite the cup seal change a fluid drop still appears at the base of the back plate. The brake pedal is hard and fluid loss is very minor. In the event of a cup seal failure does the fluid come out of the handbrake lever slot in the cylinder and run down the back? I am running DOT 5 silicone fluid and the cylinder does not appear to be worn visually. The car has not done more than 8000 miles since a full rebuild in 1993 and has always run silicone fluid since. The brake cylinder still looks like new. Perhaps the bore is oversize? I suppose the answer is to change the entire cylinder. Any other ideas?

Dave Rouget
D J ROUGET

Did you hone the cylinder? Could be that the cylinder is glazed or maybe has some high spots keeping the seals from seating properly.
Jeff Schultz

Are you sure it's not rear axle oil?
Neil McGurk

Thanks for both replies. No I have not honed the cylinder and agree that it could be an imperfect finish to the bore. The fluid is really clear and the brake fluid level does go down slowly so I'm pretty sure its not diff oil. Also the consistency, colour and smell is wrong for axle oil.

Dave
D J ROUGET

Hi Dave, I have had both rear cylinders leak on my car (just missing an accident in one case) and rather than play around with new rubbers etc - I just bought a new cylinder - better safe than sorry even though they are lot more expensive than just a repair kit.
Cam Cunningham

The copper washers at the brake hose to cylinder can get worn and leak, it was an elusive fix for my A years ago.
Fuzz
Russ Carnes

This thread was discussed between 17/08/2008 and 20/08/2008

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This thread is from the archive. The Live MG MGA BBS is active now.