Alrighty here is a quick lesson on brakes follow these instructions

1. open bleeder screw if the wheel spins free now you have a bad hose. If not you have a stick caliper.

If it is a caliper get a air compressor, remove your brake pads, place a rag between the piston and the out side, make sure your bleeder is closed then take the air gun(one with a rubber tip) place it in the hole where the banjo bolt was spray. But make sure your fingers are out of the way cause that piston will and I repeat will break your fingers. (also make sure the caliper is facing down that way the piston doesnt take off like a rocket. next remove the dust boot, then the seal clean using a old tooth brush then clean the surface of the piston. next lube the piston put the dust boot around the piston place also place the seal back in , push the piston in. If it does not want to do in do not force it in with a hammer you will wreck the square cut seal. just work it backin forth ot will go. then your just rebuilt to caliper.

2. if it is a line just replace it, cant really expalin that.

 

i find it works better if you actually put the piston against a peice of wood or something, ive had the psiton come out and hit the ground and bounce, not fun chasing those things around the garage.

 

I agree.. a lot of times what is thought to be a sticking caliper is a kinked hose[from someone hanging caliper by it, etc..]
You won't see the kink, but it keeps the caliper from retracting..