Hi all. My brakes on my GQ keep locking up after a while of driving. Ive bled the brakes. But you drive for about 10- 15 mins then they start compressing in slowly til the car stops. Dont know if after a while it builds up pressure or something but i dont know. I had to get out and crack the nipples to let fluid out. They are disc brakes on the back, anyone know what it could be?