O.K., maybe this is an old subject, but my brother called with a problem. His front brakes are locking up on his 97 4x4. Based on advice he replaced both brake calibers, but this did not solve the problem. My first thought would be the master cylinder. I don't know exactly how they work, but I would assume that there would have to be some type of relief valve or something that allows the fluid to flow back slowly. If this were clogged of malfunctioning, then this could be causing the problem. Any ideas? Please help.

 

if it aint the drums, in the back, could the brake cylinder in the drum area,

could be the LSPV?

could be the master cylinder?

 

What is a LSPV?

 

load sensing proportioning valve? i believe its over the rear axle, has a lever thingy on it

 

Would that affect the front brakes? The rear brakes are not locking up.

 

First let's clarify the problem a bit, in the title you say seizing up and in the post you say locking up. To me those 2 terms mean different things. Are the brakes locking up when braking, ie skidding tires, smoke etc; or are they seizing up and staying on after use. If it's the second I would replace the rubber lines in the front, sometimes they get swollen inside and prevent the brakes releasing. If that doesn't solve it then it could be the return port in the master.

If they're locking up and skidding when braking it could be the LSPV needs adjusted to send more force to the rears, or maybe he just needs to push a bit less

 

The front brakes are seizing (or not retracting), staying on after use. I'll have him check the rubber break lines and take a look at the master cylinder. Sorry for the confusion and thanks for the help.