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MG MGB Technical - front brakes locking up

I have 1977 MGB, the right front caliper locked up and the rotor got real hot. I changed the caliper and it still locked up, so I changed the rubber line. I took it for a test ride, now both calipers lock up. After several attempts and bleeding them, when it locked up again I immediately got out and cracked open the lines at the master and it released the brakes so I replaced the master. Guess what happened they still locked up, Any idea of what s wrong? I would very grateful if anyone Knows what the problem is.
Thanks Steve
S.E. Silvia

The only other place to look is at the hard lines. Cheers - Dave
David DuBois

Also, check the position of the brake light switch. It could be preventing the master cylinder pushrod from retracting all of the way back into the bore and leaving pressure in the system. RAY
rjm RAY

While only one doing it is usually its hose, when both do it, and particularly when cracking one bleeder releases both the problem is usually at the master. The brake light switch is a good bet for that, if it's screwed in too far it does what RAY sez. Unscrewing it too much causes the brake lights to be on all the time, and if it is as sensitive as the pedal box mounted switch it will only have one and a half turns between just turning the lights off, and stopping the pedal coming all the way back. So unscrew it, screw it in till the lights just go off, then a further 3/4 of a turn.

The other thing I've heard of with a new master and integral booster is a problem with the actuating rod, the servo stopping the master piston coming back far enough to clear the bypass hole.
PaulH Solihull

Thanks to all. Again its great that the people who blog on this site are helping to keep MG's alive. Ray and Paul "you hit the nail on the head." I followed your instructions and in 5 minutes the problem was solved. I can't thank you people enough!

Tanks
Steve Silvia
S.E. Silvia

This thread was discussed between 26/08/2010 and 28/08/2010

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