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 - how to diagnose brake problem

Hi,

I'm considering to purchase a 1978 MGB. Car runs very well with the exception of the brakes.

Brake pedal is very hard, with little stopping power. What is the most probable cause?
What are the steps I should go through to diagnose it?
How much should I budget to repair it?


Thanks in advance,

Paul
Paul

With the symptons that you describe, I would suspect brake booster problems. Sounds like the booster is not getting the vacumm that it needs to work. A booster repair kit is less than $75. That may solve the problem. There could be other problems like plugged up brake lines, too. If I wanted the car, I would not let this stop me from buying it but I would consider the likelyhood of spending a couple of hundred dollars on it to get things right.
gerry masterman

Paul, To check if it is the brake booster stand on the brake pedal about 10 times to deplete all remaining vacuum. Hold the brake pedal down hard and start the engine. If you feel the pedal "sink" toward the floor the booster is OK, if not then the booster is suspect.
If the booster IS ok then the problem is probably further along possibly in the rear wheel brake cylinders having frozen (that is corroded) and sticking in place. Cheers, Pete, Sydney, Australia.
Peter Thomas

If you haven't driven one before then the brakes on a B are heavier than on modern cars, but you should still be able to lock up the fronts even with progressively applied pressure whether the booster/servo is working or not. I drove a friends car where we had to disable the servo as it kept locking on, but after the first application just to see how much heavier they became I didn't notice again.

PaulH.
Paul Hunt

Without the booster functioning the brakes requireincreased force applied to the pedal. If the brakes do not stop the car well, it may be more than a faulty booster that is the problem. I have had my booster disconnected for a few years now and have no complaints with my brakes. They are easy to control and I can lock them up at will.

Jack up the car and have somebody apply the brakes, then try to turn each wheel. This will give you an idea of where to start, but even weak brakes can hold the wheel enough so that you will not be able to turn the wheel by hand. An alternate method is to find a gravel road. At a low speed (25MPH) quickly (progressive pressure, don't just stand on the pedal) depress the pedal untill all wheels lock, then get out and observe the skid marks.

A few hundred will get you all new brakes, plus labor.
.

carefully check that the brakes are locking each wheel.
if u have a hard pedal and no stopping then it sounds like frozen calipers and rear wheel cylinders.a common prob which will require new wheel cyls and poss shoes and drums at rear and recon calipers at front and a good time to fit ebc greenstuff pads and new discs if orig is thin or scored.also check flex and metal brake pipes when the brake system is drained .i would say the master cyl is ok as u are getting a good hard pedal.the booster only assists to make the car stop with less effort so if it is not working it just means that u have to stand on brake harder to lock up the wheels.front calipers £39 each.
this may sound drastic but the parts are not expensive
and u will have trouble free motoring for quite some time.
ronnie cathers

This thread was discussed between 04/12/2001 and 06/12/2001

MG MGB Technical index

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