Dorman braking

When the parking brake became a motor

A cable-operated handbrake failed in ways anyone could diagnose. Its replacement is a small geared motor bolted to the rear caliper, driving the piston through a screw mechanism, commanded over the vehicle network. It fails through water ingress and corroded connectors far more often than through wear.

Because the motor is sold by most manufacturers only as part of a complete caliper assembly, a failed component worth a fraction of the repair sets the price of the whole job. Dorman supplying the actuator separately is the same pattern as the rest of its catalogue applied to braking.

One warning that applies regardless of brand: an electric parking brake must be put into service mode with a scan tool before the caliper is opened, and calibrated afterwards. Retracting the piston by hand against the screw mechanism damages it.

There is a second failure worth naming. The rear calipers on electric parking brake systems seize far more readily than front calipers do, because the screw mechanism inside holds the pads lightly against the disc when parked and road salt reaches a joint that never fully releases. Replacing pads without freeing and lubricating the guide pins simply repeats the fault.