My son has been having an intermittent issue for the last several months with the right rear brakes locking up. At first, he thought it was the proportioning valve and we replaced it (see THIS THREAD
This seemed to fix the problem, but a few days ago it started doing it again. At that time we replaced the proportioning valve, the two rear wheel cylinders and the two rubber brake hoses. We also blead the fronts AND the rears. We did NOT replace the brake hardware or the drums.
The symptoms are:
1. On light braking the rear end "tucks" (lowers), but both rear brakes seem to work. (No "pulling" from the front or the rear. Stays nice and true)
2. On medium braking the right rear locks up but the left rear is still spinning. Interesting enough; even though the right rear is locked up, there's still no "pulling" from the front or the rear of the car!
3. On hard braking both rears lock up. Again, no "pulling" to the left or the right. The fronts lock up too, but you really have to brake hard.
When we replaced the rear brakes, we also replaced the front calipers, both rubber brake hoses and the pads. The only major parts that HAVEN'T been replaced is what's mentioned above (the rear brake hardware and the drums), the master cylinder, the hard lines and the parking brake hardware.
We're really at a loss here, so if anyone has seen this before, or has any ideas on what it could be, we'd love to hear from you.