Some rear disc brake pads are equipped with a metal tab which will come into contact with the disc after the friction surface material has worn near its usable minimum. The wear indicators make a constant, distinct metallic sound that should be easily heard. (The sound has been described as similar to either fingernails on a blackboard or a field full of crickets.) The key to recognizing that it is the wear indicators and not some other brake noise is that the sound is heard when the car is being driven WITHOUT the brakes applied. It may or may not be present under braking during normal driving.
The rear brake pads may be inspected without removal. With the rear end elevated and supported, remove the wheel(s). View the pads, inner and outer, through the cut-out in the center of the caliper. Remember to look at the thickness of the pad friction material (the part that actually presses on the disc) rather than the thickness of the backing plate which does not change with wear.
Remember that you are looking at the profile of the pad, not the whole thing. Brake pads can wear on a taper which may not be visible through the window. It is also not possible to check the contact surface for cracking or scoring from this position. This quick check can be helpful only as a reference; detailed inspection requires pad removal.
After the pads are removed, measure the thickness of the LINING portion (NOT the backing) of the pads. It must be at least 2mm. This is a factory minimum; please note that local inspection standards enforced by your state must be given precedence if they require a greater thickness.
REMOVAL & INSTALLATION
See Figures 1, 2 and 3
NOTE:Whenever brake pads are replaced, replace them in complete sets; that is, replace the pads on both rear wheels even if only one side is worn.
There are several combinations of shims, spacers and clips in use on these vehicles. When disassembling, work on one side at a time and pay attention to placement of these components. If you become confused during reassembly, refer to the other side for correct placement.
- Raise the vehicle and support it safely on stands.
- Remove the rear wheels. Disconnect the parking brake cable at the caliper by removing the cotter pin and then the clevis pin and washer.
- Unscrew and remove the lower caliper lock pin without removing its grease coating or allowing it to get dirty. Raise the caliper upward with the upper mounting pin serving as a hinge and use a piece of wire to tie or hold it in place.
- Release the clips and then remove the pads and shims.
- Use a tool MB990652 or an equivalent device to press the caliper piston back into the caliper. Make sure the two indentations in the caliper piston are aligned as shown. The pins on the backing plates for the pads must fit into these recesses when the pads are replaced.
- Fit the pad and shim together and then install them into the clips and in proper relationship with the caliper piston.
- Unwire the body of the caliper and lower it back to its normal position.
- Install the lock pin and torque it to 27 Nm or 20 ft. lbs.
- Reconnect the parking brake cable, using a new cotter pin.
- Replace the wheels and lower the vehicle.
- Make sure there is plenty of fluid in the reservoir. Pump the brake pedal repeatedly, checking the fluid level and keeping the reservoir adequately filled. Make sure the brakes actuate at the normal pedal position, indicating the fluid has pushed the pads directly against the disc before operating the vehicle.
- Since the hydraulic system was not opened, bleeding is usually not necessary after pad replacement.