My both front brakes lock up on my 1993 jeep wrangler i change almost every part

SOURCE: 1986 gmc sierra 1500 front rt brake locks up

check brake lines they may have gotten pinched very commonok new c/k trucks when you crank the torsion bars up to far you may have hit something and pinched the brake line check those before messing with the master cylinder those are a real pain

SOURCE: brake lock-up

I suspect that you have front disc and rear drum brakes.You did not say which of your brakes are locking up. I suggest that if your front brakes are locking {skid} that means your rear brakes are not engaging. If your rear brakes are locking {skid} then I suggest you have problems with park brake or brake fluid leaking onto the rear shoes.
More info would help me help you. I will check back soon.

SOURCE: front brakes stay locked up

You may want to replace your flexible feed lines to the calipers. Any little bit of **** in them will not let the brake fluid out of the caliper,

SOURCE: Brakes are still spongy after changing the pads, one caliper, and master cylinder. bled front brakes.

I just went to Brake Masters this morning and had them replace the Master Cylinder since I was experiencing the pedal very spongy and going to the floor. When they replaced the Master Cylinder and they gave me back the car, the brakes were still spongy and going to the floor. I addressed this to them and they took another look at it, but when I took it for a second time, the brakes were extremely spongy. It was almost like they gave me back my car in worst condition to when I brought it in. Can you help?

SOURCE: 1999 Nissan Quest. Driver side brake lock up. The

possible brake hose collapsing , interrior deterioration