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MG MGB Technical - Brakes - 70 BGT

As I was driving home a couple days ago - a couple blocks away - my brake pedal went soft. It would pump up but then the next time I tried it was soft & spongy feeling again.

I made it home, parked it & brought the midget out of hibernation so I'm still driving an MG.

Looking around I see no fluid coming out anywhere, I assume this means the master cylinder is going bad.

Not being one to let sleeping dogs lie, I opened up the MC reservoir the other day & topped up the fluid.
The very next day this soft spongy brake experience started.
Rick Bastedo

There could be a number of causes - air in the system somewhere - possibly through the master cylinder (level ?) - oil on your shoes ? - start at the back end - the rear cylinders are likely culprets - - basically examine the whole system

If you can pump it up and you get a hard pedal that will hold as long as you keep pressure on it it may be in the rear drum brake adjustment or you have a caliper piston that is backing off too far. If it won't hold once pumped up it is likely bypassing in the master cylinder.
J Heisenfeldt

"If it won't hold once pumped up it is likely bypassing in the master cylinder."

That's what I was afraid of.
Any recommendations on a replacement source?
Rick Bastedo

Bhive in SC had MC on sale --maybe worth a look
Gil Price

Thanks - Who had one on sale?
Rick Bastedo

Just adding fluid shouldn't have caused it, unless you have added an incompatible fluid and the two (original and new) have reacted. How low was the fluid when you topped it up? It's possible it was on the verge of taking in air, but then the symptoms (which sound exactly like air in lines from my experiences) should have started at least immediatley, if not before. If you can press down on the pedal, and it *doesn't* slowly sink, then the master seals would seem to be OK.
Paul Hunt 2

It was only about 20% low.
I was adding it to the clutch anyway and thought I'd top up the MC anyway.
The cap was really hard to remove, wonder if I may have deformed something when removing the cap?
Rick Bastedo

This thread was discussed between 04/03/2008 and 08/03/2008

MG MGB Technical index

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