Brake drag is caused by the brake pads or shoes not releasing completely when the brake pedal is released. If it involves only one of the front brake units, the vehicle will pull to the side with the dragging unit. Dragging brakes must be repaired immediately because it will result in overheated parts and possible damage to the braking system. There are different causes for brake drag.
Master Cylinder: Brake drag can be caused by an incorrect brake pedal adjustment. This pedal adjustment is crucial and if adjusted too tightly the vent port of the master cylinder can become blocked. The building pressure in the system results in brake drag and possible brake lockup. A slight gap should be present between the push rod and the master cylinder. A worn or corroded master cylinder bore causes excess pedal effort resulting in dragging brakes.
Brake Lines and Hoses: There may be pressure trapped in the brake line or hose after the pedal has been released. This happens when the line is pinched or kinked. During brake application pressure is high enough to bypass the kink, but when the brake pedal is released, the spring pressure of the master cylinder is not sufficient for the pressure to bypass the kink. This leaves the brake unit still applied resulting in brake drag. Brake hoses twist while replacing the caliper after a brake job. This results in brake drag at that unit. Fluid pressure can bypass the twist during application, but not return to the master cylinder after release.
Return Springs: Weak or broken return springs will result in brake drag. This happens with drum brake systems as the springs wear or become rusty.