Sticking Brake Caliper
Water contamination will result in a pitted, rusty caliper piston and bore. Caliper pistons can be made of phenolic resin or chromed steel. In time a steel piston will wear the protective chrome and nickel plating off leaving the steel piston exposed. The piston bore will become rusted and pitted from fluid contamination and dirt resulting in a sticking brake caliper.
Each caliper unit contains a dust boot to protect it from road debris and water as the vehicle travels through puddles and dirt surfaces. Inspect these boots for wear each time the pads are replaced. Overhaul kits typically contain a new boot and seal.
Square cut piston seals and other rubber components are sensitive to water, oil and brake fluid contamination. Always lubricate the piston seal with brake fluid or brake assembly fluid when rebuilding a brake caliper.
A low drag brake caliper has a groove that's cut at a larger angle than a standard. A standard caliper is cut at around a 15° angle where a low drag system is cut at a 30° angle. This allows the seal to pull the piston further into the cylinder, providing less drag on the front brake calipers for greater fuel efficiency. These systems have become popular in many late model vehicles.