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MG MGA - Binding front brakes

Hi
Just had a great 80mile plus running in drive around Cornwall. Everything working fine. However when I returned home I usually push the car in the garage but it was impossible as the front discs were binding. When cool I can push the car easily. Any ideas how to rectify. Should I bleed the brakes or is it to do with the master cylinder?
Brian
Brian Paddon

Could be the master cylinder (MS), is it standard? there is a very small hole less than 1 mm that (I think) equalises the pressure between the brake and clutch part of the MS that allows the brake/clutch fluid to return into the MS when the pedals are released. If you take off the top cover of the MS you will see the very small hole which is slightly recessed (you will have to look for it) a poke with small wire or a very very small drill with your fingers only would check that its clear. Next have you got some play on the pedal rods going into the MS you should be able to put leverage on the push rod at the MS and get free movement before the you feel it begin to move the piston in the MS. Could be a partially collapsed flexible brake hose acting as a one way valve preventing the brake piston from fully retracting. Could be a bad seal or corrosion in the slave cylinder. Clearly it is something that is creating friction and heat (binding brake)that releases as thing cool down. About the best I can suggest but no doubt the other guys will wade in.
Best Alan
AR Terry

Brian

Could be MC. I had a similar problem for a year or 3. Did overhauls of MC on numerous occasions but never sorted it. I eventually traced my fault to badly assembled calipers which I had bought new (MGB calipers). The assembler had damaged the seal metal retaining rings such that the calipers did not back off sufficiently. Only solved it with new calipers as the damaged rings had scored the cylinders.

Steve
Steve Gyles

Error. I meant scored the pistons, not the cylinders.

Did the rear wheels turn freely?

Steve


Steve Gyles

Brian

I had a problem with the seals in the master cylinder which locked up the discs. I think the seals changed shape after a period of time and covered the fill hole from the reservoir. The seals I had were very slightly longer than they should be. For a diagnostic test I loosened the end plate on the MC. This allows the piston to come out very slightly further which allowed the seals to clear the hole. I investigated several suppliers of seals measuring them all. I decided that the Caparo seals are good
see thread title "Master Cylinder holding pressure"

https://mg-cars.org.uk/cgi-bin/or17?runprog=mgbbs&access=&mode=archiveth&subject=6&subjectar=6&thread=2014062718460211593
John Francis

When it locks up next, jack the front up remove the wheel and crack the bleed nipple, if it frees up will confirm it is hydraulic. Check both sides are free, this will eliminate brake hoses (you need to do twice start with a different side each time) to eliminate the two front brake hoses. otherwise is a master cylinder issue.
Mike
Mike Ellsmore

How old is the MC, how old are the callipers and all the hoses ? Brake parts do not last forever and need replacement too from time to time
Dominic Clancy

Have come across a similar issue which turned out to be old flexibles decomposing. The debris was acting like a non-return valve,
Allan Reeling

This thread was discussed between 19/10/2018 and 20/10/2018

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