Sticking brake caliper

Q I have a problem with my 2006 Kia Picanto 1.1. The offside front brake caliper does not release fully, causing binding and excessive heat after a short run. I have renewed the offside front caliper and hose. It takes considerable force to push caliper piston inwards unless the bleed nipple is open. The vehicle is equipped with ABS and the ABS light extinguishes as normal. When pumping the pedal to bleed the system, the fluid output seems low – it takes several pumps to bleed or reset the brake pads. The brake pedal is hard to push with offside front bleed nipple open.

John Moore A There are two possible causes of a sticking brake caliper: mechanical or hydraulic. To resolve which of the systems is causing your brake to stick, you will need to jack up the vehicle and remove the road wheel. While the brake is sticking, release the bleed nipple on the caliper. If the brake frees off it indicates that the problem is hydraulic and the release of fluid allows a release of pressure.

As you have already replaced the hose, you may possibly have a problem with the ABS unit. However, first, I would check the line from the pump to the offside front caliper. Trace the pipe back to the ABS unit and loosen the pipe into the unit, then reasses the effort required to push down the brake pedal. You will, of course, need to protect the area with an old cloth to catch the escaping fluid.

On the other hand, if the brake does not free off when releasing the pressure, then the problem may be either sticking brake pads or caliper slides. This can be quite easily rectified by stripping down, cleaning and lubricating them with brake grease before reassembly.