Rear brakes sticking on after disc conversion

Post Fri Jul 10, 2015 9:02 pm

Need a bit of help people did a rear disc conversion on my 1988 320i manual non abs model but now the rear brakes keep sticking on once the car has been driven for a couple of minutes checked the servo and the one way valve there ok if I pull the vacuum pipe out the servo it releases the brakes are the master cylinders all the same on all models or is there a balance valve for the rears that is different on drum brakes to discs ???

Post Fri Jul 10, 2015 9:20 pm

i swapped the to rear disc on a 1990 non abs 320i i used the original master i had no problems.

Post Fri Jul 10, 2015 9:42 pm

gromgsxr wrote:i swapped the to rear disc on a 1990 non abs 320i i used the original master i had no problems.

So by the sounds of it I can rule out the master cylinder so is there a biased valve that can cause this problem guys

Post Fri Jul 10, 2015 10:14 pm

are the pistons on the caliper and slider pins pretty free moving?

Post Sat Jul 11, 2015 8:35 am

gromgsxr wrote:are the pistons on the caliper and slider pins pretty free moving?

Yes mate there fine it's got to do with pressure when the engine is running because once you switch off and let you pressure go on the servo the brakes will come off or if I pull the vac pipe out the servo it will release them so sleeping on it last night it points to other master cylinder or brake pressure valve

Post Sat Jul 11, 2015 10:39 am

There is a valve to the rears, its under the servo on the chassis rail next to the bulkhead, its difficult to get to. This is just a pressure valve, once the pedal is applied over a certain pressure the rears start working.

Are you sure its the rears that are stuck on, not the fronts or both?

Adjust the pull rod from the pedal mech, to the servo. Loosen the 2 17mm lock nuts at each end and turn the rod itself, it has a L/H and R/H thread either end so doing this will lengthen or shorten the rod, and will free off the brakes.

But I would have thought that either all wheels or just the fronts would be locked because of the valve I mentioned, not appilying the rears until the fronts are up to a certain pressure.

Post Sat Jul 11, 2015 11:51 am

Thanks I will check this out a˜‰

Post Mon Jul 13, 2015 9:55 pm

Update all sorted now it turn out to be were I had moved my servo across the bulk head for the engine conversion I had done the back of the glove box was just pushing on the arm going into the servo and once the car was running and the brakes pushed on and off a couple of times the arm could not come back far enough to release the pressure so with a small mod to the back of the glove box all is good now thanks guys for helping and pointing me in the right Direction to find my problem.