Front brakes staying on after complete rebuild.

DamianZ28

Active Member
#1
Hi guys, have just completed brake overhaul, all new pipes, brand new front calipers, rebuilt rear calipers, bled the whole system but the front calipers are sticking solid, undo the bleed nipples to release the pressure and they release. The master cylinder is new but was on the car when l bought it and had stood empty for a long time, could this be sticking or is it the servo? Car wont bloody start as has been off the road since last year, any ideas welcome. Many thanks Damian.
 

DamianZ28

Active Member
#5
Air valve it is then hopefully, yeah needs a good service, l haven't driven other about 20 meters since l bought it last year, been constantly working on it, changing to 5 spd LT77 manual, welding , rebuilding all suspension, BRAKES lol, cleaning painting etc so yes l can forgive it for not wanting to start. I have new plugs, leads, rota arm, distie cap oh and new water pump do lots to do if l can move it .
 

harveyp6

Well-Known Member
#6
Were the front brake hoses replaced?

Servo and master cylinder faults won't make just the front brakes lock on if it's a single line system.
 

DamianZ28

Active Member
#8
As l haven't managed to get it to all work correctly yet then l haven't been able to pump the pedal and operate the handbrake together to get the rear pads adjusted up onto the discs hence just the fronts sticking on
 

harveyp6

Well-Known Member
#9
OK so it could be all four locked on. Before diving in I'd get the brakes locked on again and see if releasing the rear bleed nipple frees them off.
 

roverp480

Active Member
#11
Had this on my P4 after a lay up, it was the servo sticking on and not allowing the fluid to return, also a sticking Master cylinder would have the same effect as would no free play in push rod.
 

DamianZ28

Active Member
#12
Whipped into the garage earlier on my lunch brake, undid the 5 screws on top of the air valve & as the last one came undone and the top became lose a hiss of air was heard and hey presto the brakes released. So could it be the valve was stuck due to lack of use perhaps, will investigate more tonight, I'll put it back together & see it works on or not. Thanks for all the input everybody:thumb:
 

cobraboy

Well-Known Member
#14
I seem to have dragged this up from somewhere, but more research is needed.......... Some air valves have two seals, and in the event of sticking the removal of one of the seals was a fix.

Perhaps someone else can verify or dismiss this ?
 

DamianZ28

Active Member
#15
hmm interesting, replaced the top and seems fine now, no sticking no matter how much l pump the brakes but see what happens when l start the engine...eventually
 

cobraboy

Well-Known Member
#16
I should be clear it is the piston seals I am referring to. If the piston is removed the system has to be bled.

Hopefully yours has freed up now.
 
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