I bought a 92 Civic LX about a week ago. 3 days ago while I was driving the brakes slowly locked up on me. It got to the point where the car would'nt move, as if I was pressing ther brake and gas at the same time. Also the brake pedal got really stiff and wouldn't move. I let the car sit about 45 minutes, came back and everything was ok, wasn't locked up and I could pump the pedal. I took the car to my mechanic and he said he couldn't find anything wrong. Today the same thing happened. What can be wrong. The previous owner said he had the brakes done not too long ago.

 

Would suggest taking out and re-greasing the caliper pins.

 

I think you should look towards brake fluid contamination. I've seen it on a pilot once. Had to replace master and vacuum bleed system with fresh fluid.