The need to rebuild the rear calipers on a 1985 Oldsmobile Toronado is generally caused by brake fluid leaking from the caliper. Both calipers should be rebuilt at the same time. Before beginning work on the vehicle you should make sure that a rear brake caliper rebuild kit is available. Otherwise, you will need to replace the calipers with new or rebuilt calipers. When working on brake components on the vehicle or on your workbench, use one assembled component as an example when working on the other component.
Tools Used: Brake cleaner, Open-ended wrench, Socket wrench, Pliers, Awl, Brake fluid, Special tool (General Motors J-23072 or equivalent), Small drift, Hammer
Rebuild the Rear Caliper
Place the rear caliper on a workbench and clean it with brake cleaner. Take the parking brake cable bracket off of the caliper using a socket wrench. Remove the retainer at the piston end with a flat-bladed screwdriver. Pull out on the piston while ratcheting the parking brake lever with your other hand. The piston will gradually come out of the caliper. Pull out the piston and the return spring. Remove the piston dust boot and piston seal from the piston bore using a flat-bladed screwdriver. Remove the parking brake lever and seal after taking off the retaining nut using a socket wrench. Pry the nylon anti-friction washer from the end of the actuator screw with a flat-bladed screwdriver. Use the butt of the screwdriver to gently remove the actuator screw. Take the thrust washer off of the actuator screw with your hand, and then use an awl --- or other pointed tool --- to take off the O-ring.
Take the two-way check valve out of the piston using a flat-bladed screwdriver. Press the new two-way check valve into the piston using your thumb. Put the new thrust washer and O-ring --- after lubricating it with brake fluid --- on the actuator screw and reinstall it in the caliper. Coat the piston seal, caliper bore and actuator screw threads with brake fluid. Place the piston seal in the bore, being careful not to twist it. Install the parking brake lever temporarily on the caliper. Insert the piston squarely in the bore and turn it with your hand to start it on the actuator screw thread. Take the parking brake lever off of the caliper.
Press the piston slowly into the bore by carefully using the special General Motors tool or an equivalent. Leave the tool in place. Slip the new nylon anti-friction washer and parking brake lever seal on the end of the actuator screw. Reinstall the parking brake lever and nut. Tighten the nut while holding the lever tightly against the lever stop. Place the new dust boot over the end of the piston and carefully tap the outer edge of the boot into the groove using a small drift and hammer. Push the inner part of the dust boot onto the piston. Install a new pad dampening spring on the piston with your thumbs making sure the ends are at the top of the caliper.
Remove the old bushings from the ears of the caliper and press in new ones using your thumb. Put a new copper sealing washer on the banjo bolt, put the bolt in the banjo fitting and put another new washer on it. Install the banjo fitting on the caliper and torque the nut to 30 foot-pounds. Reinstall the parking brake cable bracket and tighten the nut.
Tips & Warnings
Do not reuse brake fluid that has been in the vehicle or brake fluid from a container that has been open.
Do not use compressed air to clean the brake caliper. The dust from the brake pads may contain asbestos.
Use only brake cleaner, never a petroleum-based solvent, to clean brake parts.
Wear a filter mask when working on the brakes.
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