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MG MGB Technical - brakes seized?


My 1968 mgb gt has been sitting in the garage for about 3 weeks. I went to start her up and take her for a spin this weekend but when trying to back it out of the garage there was resistance and the car wouldn't move. touching the brake pedal it only moves about an inch and is very hard.

Can anyone help as to what has happened?

Did you leave the hanbrake on tight? If so the back may be locked on. Try heaving and letting of the lever and if that does not work maybe a tap on the force balancer on the back axle may do it and then see if you can get the shoes to release by "feeling" the car forwards and back, don't go wild as you can damage the brakes. Since you have one leading one trialing shoe you need to get both unlatched. Then when you get time look through the archives re care and feeding of MGB brakes.
Stan Best

Have you any room to see if it will roll forwards at all? I have had a situation where one rear brake would jam on when rolling backwards, but not when rolling forwards. Changing the adjustment cured that. The only other time has been in the winter when they have frozen on, I regularly leave my cars with the handbrake on for 3 or 4 weeks with no problem. If you can get to the wheels try and find out which one or ones are jammed by jacking p each corner in turn. Remember to chock the front wheels when jacking up the back and release the handbrake. If one front wheel is stuck fast it is quite possibly its brake hose delaminating inside and acting as a one-way valve the last time you used the footbrake.
Paul Hunt 2

To me, this sounds like a caliper starting to seize up due to infrequent use and moisture in the brake fluid causing the caliper piston to freeze up because of rust forming around its perimiter. Ray

Isn't that more likely to cause pulling to one side because that caliper isn't working rather than jamming itself on? Don't forget it was only standing 3 weeks.
Paul Hunt 2

I don't think it will be caused by a sticking caliper as i had new ones fitted about 3 years ago which had stainless steel pistons. Had new braided hoses fitted at the same time.

Also i leave the car with no handbrake on but left in gear. Garage is flat so car doesn't roll.
I have no room to push the car forward and very little room at the sides. I will try to jack the car up and see if i can move the rear wheels.

It is possible for brakes to stick on if the return path to the master cylinder is covered in the rest position. This is easy to check as opening a bleed screw on a cylinder will relieve the pressure. I did not mention this before as it's either put back right or wrong and works or it doesnt.
Stan Best

probably not relevant, but just in case - my wifes car (modern thing from ford) was doing a similar thing, only difference was that it moved about an inch before sticking solid. When i took off the drums at the back i found that on the drivers side a lining from one of the shoes had come away from the shoe and a bit had wedged itself between the drum and the undamaged shoe, effectively jamming the rear brake solid on that side. The shoes were all of 2 years old, the car is regularly driven, and nothing else was wrong, so I put it down to shoddy shoes and replaced the lot - as I am not experienced in such matters got a garage to check it out for me to be on the safe side and they said all was fine - phew, I fear garage bills at the moment. Pleased it happened on the drive and not the motorway.

Covering the hole between reservoir and cylinder can certainly cause the brakes to jam on when driving and the fliud expands, but is not really likely if it drove into the garage OK and has cooled down since. Also while that problem can affect cars with the brake light switch on the pedal cover or brake pedal where the switch is screwed in too far, it is much less likely with the hydraulic brake light switch a UK 68 has. Having said all that, the fact that the pedal is hard and has a shorter travel than usual, does imply that there is pressure in the hydraulic lines. My roadster tends to suffer the same problem, and binding brakes, in hot weather and that is due to the remote servo sticking. It is a known problem, but I have only ever heard of it happening *in* hot weather, not in a cold garage. Opening a bleed nipple will relieve the pressure in this case as well. But if there *is* sufficient hydraulic pressure to prevent you driving the car out of the garage, from either reason, then there should be sufficient pressure to light the brake lights when you aren't pushing the pedal as well.
Paul Hunt 2

This thread was discussed between 29/01/2008 and 31/01/2008

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