E12 Brake Issue

[andycam06]

I have replaced front pads and discs, rear pads and discs, shoes, handbrake cables, front slider pins, freed up the rear slider pins and freed 1 sticking rear piston but my brakes are still sticking....

My front brakes are on fire even over short trips, the rear are very warm but not mad hot.

If i roll the car 2 feet it will come to a stop as though i pressed the brakes.

This only happens 85% of the time and the other 15% it seems grand.

Anyone any ideas where to go next ?

[Raistlin]

A very common cause on these is a swollen brake hose...they deteriorate inside and swell up, causing the caliper to hold pressure and not able to return after pedal application.

It's very common on worn / aged hoses.

Pedal pressure is high enough to over-come the restriction and apply force to caliper , but return/release pressure is residual, so the hose acts as a one-way valve due to the interior swell/restriction.

Here is a simple diagnostics trick to iso the problem:

jack the suspect wheel off ground and apply the brake pedal as hard as you can...now get out and try to hand turn the wheel... if NO , open that bleeder..if the wheel then turns freely, you have a swollen hose...if it does not, you have a frozen caliper [ or handbrake bind]

Simples...

Opening the bleeder will release any line pressure to the caliper, so you then know the hose is shot, but if you release pressure open bleeder and the caliper is stll holding that wheel, it is not line pressure that is the cause because there is no line pressure with the bleeder open.

[andycam06]

i could understand 1 or maybe 2 brakes but not all 4.... ?

The front 2 are crazy hot and the rears are very warm but i would be assuming the fronts do 70% of the work so would be that much hotter..

I have been thinking some sort of value stuck slightly open ???

[Raistlin]

If the front brakes are locked on the rear ones will also have increased pressure.

Change the flexible hoses and bleed.

Have you done the diagnostic test to confirm the fault yet ?