[jeffs94]

Another cause could be rust forming behind the piston sorta locking the piston in place. VERY important to bleed the brake fluid at least every 2 years to keep moisture at a mininum.

 

[jeffs94]

You probably could but usually the rust is on the caliper which requires a light honing. If its too deep, then usually a new or rebuilt caliper is required to correctly remedy the problem and is much faster in getting the car back on the road.