MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - soft brakes

Hello all,

I took delivery of my 66 B a couple of months ago. It is an older renovation, and a beautiful driver that I operate sparingly.

I noticed this evening a good bit of pedal travel before the brakes really engage. Pumping it a couple of times firms it up, so it appears to need bleeding. The master cylinder reservoir was quite a bit low so I topped it up. I am not certain how full it was when I received it.

Now, my question. What can cause this condition? I looked for puddles on the garage floor and found none. Crawling under the corners with a flashlight and inspecting the brakes visually does not reveal any obvious leaks. Does this mean I have a leak or other brake problem or will a simple bleeding be the end of it?

Its been many years since I worked on my own vehicles much at all. I can bleed the brakes but I am a little puzzled why they need it.

Safety Fast!

JMG
JM Greenlee

JM,
You may need a master cylinder overhaul, or a new one. I had those symptoms, and a new mc fixed it. I think that the internal seals wear out, and the fluid leaks past internally instead of supplying pressure to the lines. Best, Joe
Joe Ullman

Also check the rear wheel cylinders. They
could be leaking inside the drum.
Ronald

Hi

You will find that the rear brakes are not self adjusting. Periodic rear brake adjustment and handbrake adjustment are part of owning one of these MGBs FWIW Alan
Alan

JMG; Your rear brakes may need adjustment. You say after pumping a couple of times the pedal is firm. Usually brakes that have air in the system will have a soft or spongy feeling pedal. I would insure the rear brakes are adjusted before doing anything else. Master cylinder fluid level will go down some as the brakes wear. If you do not have a repair manual it's a good idea to at least get a Haynes MGB manual. If you have an owners handbook it will show you how to adjust the rear brakes. The adjuster is on the rear of the brake backing plate, it's square and I think a 1/4" open end wrench will work or you can buy a brake adjuster tool.
With the rear wheels jacked off the floor, use a jack stand for safety, turn the adjuster clockwise until the wheel has a heavy drag when turning by hand. Back off the adjuster one or two clicks to eliminate the drag and you're done. Note, you will feel the adjuster cam each 1/4 turn, the final adjustment should be with the adjuster 1/2 way between the cam high spots. Good luck, Clifton
Clifton Gordon

I'd start by flushing and bleeding the brakes, followed by adjusting the rear shoes.
Glenn

All good suggestions given, but the loss of fluid could be nothing more than pad wear on the front brakes. As the pads wear, the pistons move further out and more fluid goes into the calipers. It is therefore necessary to periodically add fluid to compensate. You may well have unknowingly allowed the fluid level to drop to the point that you got air into the system. Even though the car is new to you, it would be a good idea to flush the entire brake system, fill with fresh fluid and bleed the system. If you do not find any evidence of leakage at any of the wheels, this is probably all you will need to do. Good luck - Dave
David DuBois

An MC leaking fluid past the piston seals will drip down the pedals onto the floor, obvious on a rubber mat, not so on carpet. The symptoms you describe do indicate air in the system, although it is not normal for this to develop on its own IME, or even with external leaks. It is possible with combinations of problems. At this stage I'd make sure the pedal (or anything else e.g. drums) shows no fluid, bleed them, top them up and keep an eye on things. The fluid level will drop during use (and increase with heat) but only as the self-adjusting front brake pads wear, which should only be very gradual. If the level drops over a period of days, or the bleeding gives you a firm pedal but they get spongy again, then its time for further work. When bleeding both mine I find a gunson's EeziBleed is useful for getting bulk air out e.g. after doing some work on them, but to get the last bits out I have to have someone stand on the pedal while I rapidly open and close each caliper bleed nipple which always gets an extra 'lump' out.
Paul Hunt

If you have a metal brake line, check how close it runs past the extractors. My B was suffering from fading brakes as a result of the brake line rubbing on the extractors. Eventually it rubbed a hole in it and every time I used the brakes I would have to pump the pedal until I got pressure.
Stuart

This thread was discussed between 02/11/2003 and 04/11/2003

MG MGB Technical index

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