I'm not sure were to put this, but I know that I need help.

I have a 93 4Runner (see below) with a mix of parts and I am having brake problems. The brake booster and master cylinder are both 97 and I have disc all around. The problem is - the passenger front caliper wants to lock up. I've swapped calipers and still no solution. I have been told that the problem could be in the master cylinder and/or the proportioning valve. I'm I correct in thinking that the proportioning valve is built into the front end of the 97 master? The master has a 10mm bolt on the lower front section and when loosened it tends to release the lock on the caliper - does this mean that the problem is in the master itself?

Any help with this would be greatly appreciated. Thanks in advance.

 

The rubber lines going to the caliper can callapse internally and cause this, it makes the act like a check valve. Flow into the caliper but no flow out. If it was the master I would think it would be doing it to both front brakes and not just on.