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MG TD TF 1500 - Leaky Brake Master Cylinder

I recently discovered that my brass sleeved master cylinder was leaking its DOT 3 fluid. The bore seems smooth and the internal rubber parts seem to be in excellent condition. Less than a thousand miles on it but about eight years on the car. I suspect that the fluid is leaking between the sleeve and the casting. Maybe from the two holes for the fluid passage or maybe at the far end.
Anyone have any experience with this and know what to look for to confirm my suspicions? Any fix?
Jim Merz

The rubber parts aren't swollen from DOT 3? They must be making them out of better stuff than any I've had. Or your DOT 3 was better than any I've tried (longer than 8 years ago).

Sorry I don't have a good answer, but 8 years is longer than I've ever been able to keep a hydraulic system buttoned up with DOT 4.

Hmm, now that I think about it, maybe I am using DOT 4 fluid. I used all the fluid in the can to flush all the old fluid and pitched the can so I can't check it. I mentioned DOT 3 to confirm that I am not using Silicone fluid.
Jim Merz

I had the same problem with a brass-sleeved MC. I eventually gave up and bought an new master cylinder.

It was leaking between the sleeve and the casting. I used DOT 4 liquid, and I rebuilt the damn thing 4 times before I pulled off the accordion seal on the outside and bench tested it. It became pretty obvious that there was enough of a gap between the sleeve and casting by the fluid and bubbles weeping out between the brass sleeve and cast iron cylinder.

FWIW, Apple Hydraulics sleeved the MC.
Mark B.

Thanks for the comment Mark. Phil Marino out in CA did mine. Maybe that's a chronic problem with sleeving a cylinder. Or could it be the DOT 4 eating up whatever sealant was used between the sleeve and the casting?
Jim Merz

This thread was discussed between 07/08/2006 and 09/08/2006

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