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MG MGB Technical - Rear brake cylinders leaking

Just bought a '67 MGB GT Special this summer. It's in pretty rough condition, but basically I'm hoping to tinker with it on my college student budget until I get a real job and a real garage.
The car had no brake fluid when I bought it, which I assumed was because of the soggy seals on the rear brake cylinders. Long story short, I ended up having to replace the rear cylinders after inspecting the insides of some fairly corroded original pieces. This doesn't seem to have fixed the problem. I still seem to have brake fluid leaking from the rear cylinders. The old brake lines look pretty ratty...could that be the problem? Anything I might have missed?
Thanks.
Richard Rykens

Richard, Are your brakes ok after changing the cylinders? Are you sure that you are seeing
brake fliud rather than differential oil, the rear axle seals could be leaking oil. The old brake
lines will not cause fluid to leak from the cylinders assuming the fitting to the cylinder is
sealing properly. If you have fluid/oil around either of the brake drums, remove the drum and
you should be able to see source of the leak. Good luck. Clifton
Clifton Gordon

I'm sure it's brake fluid, because when I take the drums apart, it's definitely coming from behind the brake cylinder. If the brake fitting isn't sealing properly, is that an issue where I need new brake lines?
Richard Rykens

Richard, The fitting should tighten enough to stop the leaks unless it is cross threaded into
the brake cylinder or the fitting is rounded off so a wrench will not tighten it. If your fittings are
good try removing them from the cylinders and carefully screw them back into the cylinders,
you may have to wiggle or move the lines a little to get the fittings started, they should start
by hand and turn a few turns before using a wrench for final tightening. If the fittings are junk
it's best to replace the rear lines, they are attached to a three way fitting on the right axle tube.
When working on metal fuel or brake lines that connect to a fixed component you should
always use care to insure the fitting isn't cross threaded, as I said hand start and don't put
a wrench on the fitting until you are sure the fitting is not cross threaded. Using the hand fitting
technique on brake and fuel lines will prevent most connector leaks and save you a lot of grief.
Hope this helps, Clifton
Clifton Gordon

It depends what is leaking. If it is the cylinder seals then your cylinder is bad. If it is from where the pipe connects to the cylinder then you could have crossed threads on the fitting, trapped some dirt, damaged the flare on the pipe etc etc. Or the pipe could be rusted through and/or have cracked when you changed the cylinder. You will have to look and see precisely where the leak is coming from.
Paul Hunt

Richard,

It sounds like the brakes are very questionable, at best. I would definitely replace the brake lines on the rear axle. The good news is that you can probably find them locally. You need to find an old-fashioned auto parts store, where the employees actually know something about cars; not one of the big chains. The lines you want have what is known as a "bubble" flare. The fittings have the same thread as any other cars. I did mine a couple of years ago, when I bought the car. I don't remember the lengths needed.

There is a rubber hose from a tee-fitting on the right side of the rear axle to the brake line on the body of the car. This hose should also be replaced. I don't know if you can get these locally. I wouldn't be surprised if you could.

In any event, go to http://www.mossmotors.com and order a free catalog. You'll need it. Not only is it Moss the largest importer of parts for these cars, but the exploded diagrams can be invaluable. Then go to an auto parts store that sells Haynes manuals and order the one for the MGB. It should be less than $15. There are quite a few Moss resellers that will sell you parts, using the Moss catalog numbers, for 10-15 less than Moss prices. One I like is the LBCarCo in Michigan. http://www.lbcarco.com
Paul Noble

This thread was discussed between 07/10/2002 and 08/10/2002

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