Brakes stuck on !

[Peter Collins]

My latest problem I need help with on the Forum is with my brakes . I have had the brakes renovated professionally but when I apply the brake pedal without the engine running ( so no vacuumed being involved ) the pedal goes rock hard and brakes are stuck on . If I start the engine up the brakes will release for a time . I thought it may be problems with the servo or the master cylinder so I returned them to the brake man who stripped and re checked them and he said they were fine . I have refitted them and the problem still persists . The only way to release the brakes is to undo one of the unions on the servo , then the brake lights go out .This problem has got me really scratching my head ! Before the brake pedal goes hard there is free play between pedal and the master cylinder . I have ruled out vacume because the engine is not running when it happens , it is almost as if the servo is not letting the brake fluid return / master cylinder ..

[mgcjag]

Hi Peter....had similar problem ...was the small piston/pin that operates the reaction valve with the engine off and brakes locked remove the plastic end of the valve to release pressure but cover with a cloth as the piston may fly out....Steve

[PeterCrespin]

My latest problem I need help with on the Forum is with my brakes . I have had the brakes renovated professionally but when I apply the brake pedal without the engine running ( so no vacuumed being involved ..

Just because the engine isn't running doesn't mean there's no vacuum involved - that's what the reservac tank and check valve are there fore. If it releases when hou start the engine it sounds like you may have the plumbing wrong. Only if you disconnect the vacuum on both sides of the servo do you know for sure that vacuum and mis-connection are not involved. Start from there and see if the brakes release normally. Only if they stick with no vacuum anywhere near the system do you know for sure it's an hydraulic problem.

Pete

[Peter Collins]

Hi Steve , thanks for your reply but I have already tried that and you can hear the air being dispersed when you press the brake pedal . Pete

Hi Peter that was the first thing I tried , i discoected both pipes from servo and brakes still stuck on . Pete

[christopher storey]

This is a very common problem on 4.2 cars with the remote servo. Modern brake fluids lack the slipperiness of the old fluids, and the result is that the shuttle in the servo has a tendency to stick. I eventually solved it on mine by dismantling the servo cylinder - again - and thoroughly lubricating everything with red rubber grease, of which I bought a lifetime's supply ( 1lb jar ) from the Morris Minor centre. You could try dissolving a good quantity of rubber grease in some dot3 or dot 4 brake fluid and flushing the system through with it, which might just save you having to dismantle yet again

The only other possibility which occurs to me is that you have a flexible hose in which the internal bore has collapsed, but if these have been renewed this seems unlikely