my uncle and i were changing the pads on his 96 f150 yesterday and before i got there he had the passenger side caliper off and i think he pressed the brake and pushed the piston out too far and when i got there i put a big c-clamp on it and it was very stuck it wouldnt go back in at all it even bent the c-clamp (the biggest 12 inch clamp they have at home depot). by this time he called autozone to get a new one so i took the brake line off of it and had the caliper sitting on the ground and i finally got the piston to move back in by pounding on it with a hammer and when i did this there was fluid squirting out of the rubber boot around the piston so we just went ahead and got the new one and put it on just to be safe.

I'm wondering what would cause the seal inside on the piston to break and cause the caliper to hang up like that. ive done my breaks probably 20 times with all the vehicles ive had and ive never had a piston stick like that. its not an issue any more since we replaced the caliper but i just want to know so i dont accidently do it and have to buy a new caliper.

thanks

 

The piston must slide in perfectly straight. When you use a c clamp to push it in, you can easily get the clamp slightly off center pushing the piston in at an angle. That's what got hung up. As for the boot, yours is ten years old (assuming it's original). They get hot and move around, and pressing the piston back in was the ultimate thing that made it leak. FWIW, I use C clamps too, but I use an old pad so the clamp isn't directly on the piston.