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 truck 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 0.08 in. (2mm) for all 1992-95 Monteros. This is a Mitsubishi 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 through 6
Whenever brake pads are replaced, replace them in complete sets; that is, replace the pads on both front wheels even if only one side is worn.
There are several combinations of shims, spacers and clips in use on Mitsubishi 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. To remove the brake pads:
- Raise the vehicle and support it safely on jackstands.
- Remove the front wheels.
- Siphon a sufficient amount of brake fluid from the master cylinder reservoir to prevent the brake fluid from overflowing when installing new brake pads. This is necessary as the piston must be forced into the cylinder bore to provide clearance to install the caliper with the new pads.
- Unscrew and remove the lockpin without disturbing the grease coating. Place the pin in a clean spot where grease will not pick up dust. Lift up the caliper body by using the guide pin bolt as a fulcrum. Fasten the caliper in the raised position with wire.
- Remove the shims, brake pads and spring clips in order. Depending on the number of such components, either diagram their placement or lay them aside in order.
- Clean the surface of the piston with a clean, damp rag. Make sure there is room in the master cylinder reservoir for more fluid (fluid will be forced back into the reservoir in the next step). If necessary, remove some fluid with a clean squeeze ball syringe.
- Use a large C-clamp or similar tool to depress the caliper pistons back into the calipers. The pistons will need to be almost flush with the case to fit over the new, thicker pads.
- Install the brake pads with the shims, clips and fittings in the correct order. Vehicles with upper and lower spring clips for each pad should have these clips replaced with the pads.
Keep the brake surface of each pad free of grease, oil and fluids during the installation. A greasy fingerprint or similar light contact may be removed with a commercial brake cleaning spray.
- Remove the wire, lower the caliper into position, and screw in the lower lockpin. Make certain the rubber boot is correctly placed on the lockpin and is not pinched or deformed.
- Replace the wheels and lower the vehicle.
- Pump the brake pedal several times with the engine off. The first two or three pedal strokes may be longer than usual as the pistons return from their compressed position and drive the pads inward. After a reasonable feel has been achieved, check the master cylinder reservoir and top up the fluid as needed. Start the engine and pump the brake pedal again, checking for the proper feel and engagement point.
- Since the brake hoses and hydraulic system was not opened during the repair, it is usually not necessary to bleed the brake system after pad replacement. Use good judgement in determining pedal feel; bleeding may be necessary for other reasons.
Braking should be moderate for the first 10 miles (16 km) or so until the new pads seat correctly. The new pads will bed best if put through several moderate heating and cooling cycles. Avoid hard braking until the brakes have experienced several long, slow stops with time to cool in between. Taking the time to properly bed the brakes will yield quieter operation, more efficient stopping and contribute to extended brake life.