How to replace rear brake pads on 2002 buick rendevous

Those are special calipers. The piston cannot be just compressed back into the caliper - it needs to be turned as it is compressed or you can ruin the caliper.There is a kit you can rent from AutoZone or many independent auto parts stores that will perform both functions at the same time.
Block fron wheels and raise vehicle passenger side. Remove wheel. The caliper is on the top rear side of the assembly you're looking at.There are 2 long bolts you'll need to remove to take the caliper off the vehicle. Don't remove the brake line or open the bleeder screw ( either of these moves will add to your work!! ) Insert a large flat blade screwdriver in between the rotor and outboard brake pad and pry away from the vehicle slightly to release the pads from the rotor. Slide caliper upwards and towards the back of the vehicle to separate from rotor. The pads will come in a full set ( all 4 pads for both side of the rear ) . Look at your replacement pads and determine if they have a retainer clip holding them in place or a compression clip. Remove outboard pad first then inboard. Match old pads to replacement pads. Inspect rotor for grooves and irregular surfaces - if any grooves or irregularity present, remove rotor and take to an auto parts store for refinishing.Compress caliper piston with kit and allow 5 minutes for pressure to bleed back into the master cylinder.install rotor if removed and wipe surfaces with brake clean. Install inboard then outboard pad and place caliper on rotor, then mount to vehicle. Install wheel, repeat procedure for drivers side, then PUMP BRAKE PEDAL 5 TIMES BEFORE TRYING TO DRIVE VEHICLE to set pads on rotors.