BMW E46 Brake Caliper Seizing and Rear Brake Drag
Why does the E46 brake drag or overheat?
The most common cause is a seized brake caliper piston or seals. The slide pins can also seize. On the rear wheel, drag can be caused by the handbrake shoes coming loose when the mounting point on the backing plate has rusted.
Is cleaning the brake caliper enough or does the caliper need to be replaced?
Cleaning and new seals are enough if the piston is not corroded. Polish the piston surface and the seal groove clean and recondition the slide pins at the same time. If the piston has long-running corrosion, renew the piston or the whole caliper. Merely loosening it up helps only for a short time.
How is the brake caliper piston pushed in, and what size is the front caliper piston?
The piston is pushed straight in with even force; it is not turned. If it does not move with reasonable force, the seal is broken or the piston has corrosion. The front caliper piston (34116758113/4) has a diameter of 54 mm, and on the 330i 57 mm. Measure before ordering.