Im bleeding the breaks on a 91 chevy c1500 the front calipers are locking down and not releaseing

First thing to check is the slide pins on the calibers. Make sure they are clean and free of any rust. If not, replace them. If they are not rusty then clean & lubricate them with a very small amount of grease. Your brake system on this vehicle is 20 years old. Have you ever changed the brake fluid? If you are like most people the answer is no. I recommend you flush the entire brake system and install fresh DOT3 fluid. Look closely at the flexible brake hoses that connect to the caliber. They may be collapsing and I recommend you replace them on a 20 year old vehicle. I would also recommend you replace the calibers on the front. With new calibers, brake lines, and fresh fluid you should have great brakes. If you still have the problem replace the master cylinder.