i have a 89 na that after 5 minutes of normal driving the brakes feel like they are grabbing, after about 1 more minute all 4 wheels start to lock up. to the point that the brakes start to smoke. it seems like the rear wheels get hot first. i rebuilt the calipers in the back thinking it is a sticking piston but that hasnt worked.

 

Samething happed to my buds ride (85 gsl). It turned out to be a bad caliper, something with a faulty piston grabbing from too much pressure buildup in the fluid. Hope that helps.

 

could be alot of things. Blead it and check for leaks. Might be a leaky caliper causing one break to lock up but not all of them. If they are grabbing hard sounds like air in the system. Check the master blead check blead and you will find it.

 

It's a sticking caliper.

 

he said all 4 wheels are locking up? Am I mistaken? Are all 4 locking?

 

it is all four wheels but the rear wheels get hot first, then all wheels lock up. i think it is a sticking caliper as well but i cant find out which one

 

I would flush the fluid and make sure the brake booster check valve is on correctly or on at all. I don't know but that might have something to do with it. Speedbleeder.com, they're awesome.

 

Check pedal adjustment, brake booster, and e-brake mechanism (a little spring loaded cam on the rear calipers) for stickiness.

A sticking caliper isn't going to effect the other calipers. Since all wheels are effected, start with the MC side of the system (pedal, booster, MC). There are tests and setups for these in the haynes manual and the FSM.

 

I've had this happen to me before on my '89 323. I had just installed a brand new power booster and it was faulty. Ruined my brand new front brakes too.