I decided I needed a daily so I found a 92 civic sedan LX 5spd for $100. Story on it is it sat behind a used car lot for several years before someone bought it. It didn't run at all when I got it, someone had put a ton of new parts on it and gave up on it. I just put valves and piston rings in it. Got it running and driving good. I did all of this at the shop I work at. I went to drive it home, got halfway there and the brakes locked up. All 4. So I sat for a few minutes waiting on Sombody to bring me some tools. By the time they got there the brakes had free'd up and I was able to drive it almost back to the shop before they locked up again. I can drive it for 10-20 minutes just fine, then the brakes lock up. If i let it sit for 15 minutes they're fine. When the brakes are locked up the brake pedal is really stiff and hard to push. I got it on the rack and found that it has new calipers, pads, and hoses on the front. New wheel cylinders, and drums on the back. Couldn't really tell how new the shoes were but they looked pretty good. I found one other thread similar to this, dude said he replaced MC and brake booster. I figure it has to be somthing that has to do with all 4 brakes, so it has to be the booster, MC, or Proportioning valve. I'm about to order a MC and Booster. Just wanted to know if anyone had any insight as to why it's causing the brakes to lock up? I replace boosters all the time at work, but usually they just cause a stiff brake pedal, I don't see why they should make the brakes stick. Really hoping someone can point me in the right direction

 

Adjust the brake light switch and/or the stop nut on the pedal side of the booster so that the pedal returns higher. If the master cylinder piston doesn't come all the way back, pressure will build up and make the brakes drag.

 

Check the clearance between the booster push-rod and master cylinder piston. Adjust if its too tight, about 1 mm. . I Forgot the exact specs, kindly do a little search.

 

I don't think all of your brakes are locking up, you might want to inspect your brakes more closely to see what the deal is.

 

I have had exactly what the OP described happen to my car. The brakes don't "lock up" abruptly but they drag more and more until the car cannot move.

This happens because, for whatever reason, the master cylinder piston isn't able to return to the fully back position when no one is stepping on the pedal.

 

It's either the brake booster isn't adjusted right inside the car and there isn't any free play or the brake booster and master cylinder aren't a matched set and the pin on the brake booster is too long.

 

Yes!! This is exactly what happen to me. The break pedal stopper, the little rubber piece on the break pedal that touches the break light switch, broke off. I installed a new rubber stopper and it was a little thicker so the break pedal was not fully releasing. Thank you for this info!!!