Rebuild or replace the caliper. Remove the caliper, remove one pad, carefully press the brake pedal to pop the piston out. Cover the caliper with a shop rag first and DON'T stomp the pedal, just carefully press it until the piston is released. Clamp the brake line off carefully. Loosen the brake line fitting and remove it. Remove the pad and the piston. Clean the piston thoroughly, checking for damage such as nicks and scratches. Buy a rebuild kit at any parts store. Buy a bottle of brake fluid. A brake hone is a great idea, but not necessary. Remove the old dust boot and seal. Use a very fine sandpaper to clean the piston bore. Thoroughly flush the piston bore with brake fluid or brake cleaner. Moisten the new seal and install in groove. Place the new dust boot over the piston and press the piston into the bore by hand after lubricating with brake fluid. Make sure the piston bottoms out in the bore. Reinstall the pads and brake line. Reattach the caliper and tighten the brake line.

That should fix your problem.

Answered by rivermikerat (expert)
5,494 answers provided