Before beginning replacement of the rear brake caliper inspect the brake master cylinder reservoir for its fluid level. Drain fluid from the reservoir if its level exceeds the midway point between maximum and minimum marks. Lift your vehicle safely. Take the tire and wheel system out to work on the brakes. Press the caliper pistons back with a c-clamp placed over the top of the housing while squeezing the clamped end against the back of the outboard pads. Tighten the c-clamp until the pistons fully move towards the rear. Use compressed air to clean the brake hose and protect fluid from leaking out when you install a rubber seal. Untighten and remove the brake hose to caliper bolt while abandoning the two copper brake hose gaskets. First remove the brake caliper guide pin bolts before taking the brake caliper off the vehicle. Inspect the caliper assembly. Install
Brake Pads by putting a c-clamp to hold brake pistons in position at the bottom of the caliper bores while protecting them with old pads, metal plate, or wood. Hold up the inner side of the caliper boot with a small flat tool to let air escape below the piston level. Position the brake caliper on its mounting bracket and apply brake cleaner to threads of guide pin bolts before installing threadlocker gm p/n 12345493 onto the bolts for installation. Secure the guide pin bolts into their positions at 34 n.m (25 lb ft) for the 15 series and 72 n.m (53 lb ft) for the 25/35 series. Insert 2 new copper brake hose gaskets into the brake fitting and then connect the brake hose by tightening its bolt to 40 n.m (30 lb ft). Squeeze the brake to remove air from the lines then attach the tire assembly with wheel. Drop the vehicle below ground level and refill the master brake reservoir through its top opening.