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MG MGA - Brake Question

Over the weekend I experienced an issue with my brakes that had been building over time.

Basically I was getting a chirp from the left front brake. It sounded as if the brake pad wasn't retracting fully after I'd let up the pedal. I've noticed it over the past couple of weeks.

Just to check things out I opened the master cylinder to make sure it was full, which it was.

After I opened the MC fill valve and screwed it back in again the noise abruptly disappeared. Obviously I relieved some form of vacuum that had been building. Is this normal? Is there supposed to be a small hole in the cap to balance the air? what gives?
T McCarthy

This can also be caused by the flex lines starting to break down internaly . This will restrict the reverse flow from the wheel cylinders.
Sandy
Sandy Sanders

Thanks Sandy. The brake lines are only about 18 months old.
T McCarthy

The filler cap on the master cylinder definately needs to be vented. There is no other vent on the master.
Jeff Schultz

Modern cars usually have a flexible rubber gasket to keep air from getting to the fluid while still preventing vacuum buildup. The problem with air is that it contains moisture that can condense into the fluid. I have seen some caps for other cars that have a rubber bellows built into the cap to prevent air getting to the fluid, but don't know if such is available for the MGA.
Jeff Schultz

As a follow up to Jeff's point. As you apply and release the brakes, sometimes hundreds of times a day, each time you draw air into and out of the master cylinder.
Air contains moisture and normal brake fluid is hygroscopic (attracts moisture).
Each cycle of air in/air out will leave moisture in the fluid. This fluid lowers the boiling point of the fluid and causes corrosion.
I had an idea once, but never tried it. Solder a small diameter tube to the inside of the master cylinder cap, where the hole is, and fit a small party balloon to the tube.
Air can now enter and leave the master cylinder without coming into contact with the fluid, in the same way as the bellows on modern cars.
The balloon does not need a very firm fastening to the tube as it always has only atmospheric pressure inside.

P.S. Silocone fluid is not hygroscopic.


Mick
Mick Anderson

Silly thought # 267.....

How about placing a condom over the threads and then tightening the cap?

Is there enough clearance in the threads? It should provide the same "protection" as the modern rubber seal.

Maybe someone with a spare can give this a try. If it fits, it should do the job. Think I'll market it for $4.95 each.

Chuck
Chuck Schaefer

Before you use a balloon or condom be sure and immerse it in brake fluid for a few days and see what happens. You don't want to introduce a bunch of small particles of disintegrating rubber-like material into the brake system.

FWIW

Larry
Larry Hallanger

All the "creative" solutions are unnecessary, though humorous, if you either change the fluid at least every two years or use silicon and change it every four years. With proper maintenance what was designed 50 + years ago still works great.
R J Brown

This thread was discussed between 16/05/2007 and 18/05/2007

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