What would cause the brakes not work right on a 1992 PF after replacing master cyl. all pads cal is part under passanger side frame where brake line runs to before rear end?

1. Air in the brake lines. This is the most common cause of brake problems after replacing the master cylinder. Air can get into the lines when you disconnect them to replace the master cylinder, or it can leak in through a damaged brake line. Air can cause the brakes to feel spongy or unresponsive, and they may not work at all if there is too much air in the lines.

2. Incorrectly installed brake pads. If the brake pads are not installed correctly, they will not be able to apply pressure to the rotors and the brakes will not work. Make sure that the pads are seated properly in the calipers and that the caliper pins are greased.

3. Damaged brake rotors. If the brake rotors are damaged, they can prevent the brake pads from making contact with them and the brakes will not work. Check the rotors for any damage, such as cracks, grooves, or warpage.

4. Leaking brake line. A leaking brake line can cause the brake fluid to leak out, which will reduce the pressure in the brake lines and cause the brakes to not work properly. Check the brake lines for any leaks and replace them if necessary.

5. Faulty master cylinder. If the master cylinder is faulty, it may not be able to generate enough pressure to push the brake fluid through the lines and to the calipers. This will cause the brakes to not work properly.