Brakes sticking on

[RoverP6B]

I have just overhauled the Lockheed single line brake booster in my Rover P6B, and now to my dismay the brakes are not releasing after an application of the pedals.

The harder the application, the tighter they lock.

I have had a booster do the same but to a lesser degree some years ago. The brakes would stick only on light applications. Hard applications would see no problem. On that occassion, I returned to booster and received a replacement.

This booster was used in the car from 1990 till 1998. The slave cylinder had been resleeved prior to 1990. I have now rebuilt this booster.

I fitted a genuine Lockheed kit, and followed the instructions to the letter, comparing and cross referenceing to ensure no mistakes were made.

I did notice that both the piston assembly within the slave cylinder and especially the air contol piston after fitting the new rubber seals were very tight within their respective bores. The air contol piston especially so!

If this air contol piston were to stick, would that result in the brakes remaining on after an application?

Any help will be greatly appreciated.

Ron.[/img]

[katanaman]

I had this problem in the past as well but never investigated it to be honest. Just out of curiosity what happens if you pull the vac pipe off and the the system go to atmosphere? This should tell us whether its a hydraulic problem or an air problem.

[ChrisJC]

Check that the master cylinder / slave servo move back far enough to allow excess fluid back into the mastery cylinder. I don't know if the slave servo has any adjustment, but with a non servo system, I know that if you over-adjust the master cylinder, you effectively block off the return to the reservoir, so it won't release the brakes when it's warmed up.


Chris.

[RoverP6B]

I did a few tests this morning,...removed the vacuum pipe from the servo vacuum chamber, and started the engine. Pedal felt smooth and moved tha car back and forth with no brake sticking that could be felt.

Reconnected vacuum hose, started engine with foot on brake pedal, and the pedal dropped slightly as is it supposed to do. Pressed the pedal, which felt heavy and lumpy, into reverse..brakes locked on.

Removed the air control valve chamber mounted on top of the slave cylinder and replaced with another...no difference.

So...feeling exceedlingly pi55ed off removed the servo and put another new Lockheed kit through it.

Checked, double and triple checked everything. This time around, the operation of the assembly by hand felt smoother.

It is now back in the car, and it will sit till Sunday night when a friend is coming over and we will bleed them.

Fingers crossed

Ron.

[RoverP6B]

Well we bled the brakes, and then took Rover for a test run.

Success

The brakes felt fantastic, really responsive with not the slightest hint of any drag.

I am very pleased indeed!

Ron.