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MG MGB Technical - Front Brakes Binding

I rebuilt the master cylinder on my 1969-B. Now the front brakes are staying bound tight after appling presure. They weren't doing this before. I rebuilt the cylinder due to they wouldn't hold preasure. I have diconnected the lines from the cylinder and it does not relieve the presaure. So I don't think it is the cylinder malfunctioning or built incorrectly. When I loosen the bleeder valve the preasure releases so I can move the pistons back in. Could it be the calipers are sticking to much to move on thier own? or could it be something to do with the four way connecter mounted on the finder well?
David Whetsel

Since disconnecting the lines at the master cylinder doesn't help, the blockage is lower down and is almost certainly the flexible hoses. If they are old they can disintegrate internally while still looking fine externally. Change them.
Mike Howlett

I had a similar problem, but mine was minor. Just a light kissing between the pads and rotor. I sprayed silicone on the external part of the piston at the seal and the problem disappeared.
Frank Grimaldi

David -

I do not remember if the 1969 has the brake light switch on the master cylinder housing. If it does, you need to loosen the brake light switch...it doubles as the control for the brake pedal travel adjustment.

Martin
Martin Connolly

Also sounds to me, like degenerating flexibles, change all three if that is the case. Then replace the fluid.
Allan

Switch to stainless steel braided brake lines if you have the funds. I agree with the colapsed hose diagnossis. Or possibly the pistons are sticking.
S.L. LaPaugh

Check the bolts that hold the master cly. Mine were loose and the housing tilted forward abd jamed the rod. Both front wheels were locked up. After securing the nuts, which are a devil to get to, everything went back to normal
CCN Charlie

"it doubles as the control for the brake pedal travel adjustment"

Only as 'an undocumented feature'! It will restrict pedal return causing brake sticking on if it is screwed in too far, but it is not intended to! When correctly adjusted the pedal should come back all the way, and still leave a bit of movement in the switch. This applies to the pedal-box mounted switches as well as the later cabin-mounted on cars with dual circuit and servo.

On the way back from the Yorvik run last weekend something didn't feel right, and I found the right caliper dragging a bit. Hub was only a bit warmer than the other, so although it had blued the disc I suspect it was something that had happened then partially cleared as the hub was completely cool by the time I got home. Even though the pistons move in and out relatively easily and are shiny and uncorroded that wheel does drag more when the brakes have been applied hard and released. There are bits of rubber sticking out from where the piston goes into the caliper so I suspect the dust seals have had it. I did slacken the bleed nipple that side which made no difference to the drag so I'm going to replace calipers, discs and pads both sides, quite a lot of material has crumbled off the edges of the pads that side.
Paul Hunt

On a similar topic. My 76 MGB GT has been off the road waiting on new calipers, pads and disks because the front brakes where binding. Finished job about 3hrs ago but binding problem was not cured. And found reference to the brake light switch io the pedal box cover. I removed the switch and brake binding problem has vanished. See link below.

If you have a switch on the pedal box and binding brakes I would recommend removing the switch, count the turns just incase it is not the issue.

http://www2.mgcars.org.uk/cgi-bin/gen5?runprog=mgbbs&access=&mode=archiveth&subject=71&subjectar=71&thread=200607032108405537
T I Lyons

This thread was discussed between 12/05/2009 and 07/06/2009

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