binding back brakes

[boris123]

hi folks i am having trouble with binding back brakes the wheels spin free when cold but as i go on a run they start to bind and get hot they eventually seize solid some times causing loss of brakes. as the brakes cool they free off. i have replaced the rear shoes,cylinders,front pads and master cylinder. the mandrake cables are free and the drums are not adjusted up too much. anyone had similar problems

[CovKid]

Springs correctly fitted?

[simoncummins]

The only thing left is the flexy hoses have perished on the inside and are not letting the fluid return correctly but this would happen when cold as well .

[marlinowner]

Wonder if a faulty brake bias valve could cause this? Maybe not a temperature fault, rather the binding gets worse with each brake application, when you stop then the pressure gradually reduces, and the brakes also cool down.

[silverbullet]

Its an inertia valve, not a residual pressure device. Unless it is completely full of rust and cack, preventing the valve from returning.
Doesnt explain the temp symptoms though. Sounds like the rears are set up a bit close.
Has the brake fluid had a full flush through / change?

[boris123]

Thanks for the help

The flud has been changed and flushed through along with the master cylinder, rear break cylinder and rear flex hoses. But the breaks are still starting to bind the more I use them.

Where are either of these valves youve mentioned located on the van?

[CovKid]

I think it'll be worth your while popping the drums off and comparing the spring fitment to that in the WIKI. They're the only thing that pulls the shoes back post-braking (apart from wheel cylinders relaxing). Tis possible to fit them incorrectly.

[bigherb]

Has the brake master cylinder push rod got enough clearance? Is the brake pedal return spring pulling the pedal back fully?

[boris123]

Yes to both of those, ive looked at the bias valve online but no idea where its located on the van, anyone know?

[silverbullet]

There is no bias valve. There is an inertia valve located over the steering rack, rhs of tunnel iirc

[boxer]

Hydraulically there isn't much to go wrong. I've never had a hydraulic problem where the pressure has increased progressively due to non return usually leaks is the issue.

From a complexity point of view the handbrake and the shoes themselves plus attendant springs, cables etc are far more likely to cause the problem as there is more to fail.
You seem to have changed just about all of the hydraulic components anyway, was this as a part of the attempted cure or an unrelated process that has lead to the problem. If it was unrelated check the new hoses are not kinking when you drive/load the van.

Try writing down everything that happened ( re the van and brakes) from about a month before the problem started. Examine the time line and go back to anything that occurred in line with the problem. Don't dismiss anything as ridiculous just check it.