Brakes locking up on 74 mgb

[Buick35]

This happened to me before,when driving my car sometimes will  loose power because the brakes will come on.I then have to pop the hood and crack open a brake line on the master cylinder and then it will roll. I recently replaced all the rubber brake hoses. The p/o ran silicone brake fluid in it so I serviced it with the same.Could the master cylinder be bad? It's got a new switch also.Thanks

[mike6024]

I think the brake M/C piston may not be retracting all the way if you know what I mean.

 

[Buick35]

Thanks

[mike6024]

https://www.mgexp.com/forum/mgb-and-gt-forum.1/new-78-b-brake-booster-cylinder-install.3719837/

 

some of this talks about the rod adjustment, and some other possibly relevant things.

 

[Buick35]

Thanks,mine dose not have a brake booster though.I think I'll replace the master cylinder and see what happens.Greg.

[oldcar]

Basically what is happening is that the piston in the master cylinder is not returning sufficiently to allow the fluid to drain back correctly.  Each time you apply the brakes the fluid builds up a little more,  eventually preventing the brakes from "comming off" . i.e. Locking on!

Probably a rebuilt master cylinder and a full flushing of the system and finally a complete change to new fluid will cure your problem.  Hydraulic brakes used to require a complete flush and new fluid every two years. Today no one bothers until there is a problem. Even "modern" hydraulic fluids are not intended to last for ever.

 

Bj

Edited February 13, 2020 by oldcar (see edit history)