Replacing brake pads

Part 1. Preparation and safety

Objective

• Replace brake pads and refit according to the manufacturer's recommended procedure.

Personal safety

Whenever you perform a task in the workshop you must use personal protective clothing and equipment that is appropriate for the task and which conforms to your local safety regulations and policies. Among other items, this may include:

• Work clothing - such as coveralls and steel-capped footwear
• Eye protection - such as safety glasses and face masks
• Ear protection - such as earmuffs and earplugs
• Hand protection - such as rubber gloves and barrier cream
• Respiratory equipment - such as face masks and valved respirators

If you are not certain what is appropriate or required, ask your supervisor.

Safety check

• Make sure that you understand and observe all legislative and personal safety procedures when carrying out the following tasks. If you are unsure of what these are, ask your supervisor.

Points to note

• Before you raise the vehicle, you will need to remove some of the brake fluid from the master cylinder. Using a siphon, remove enough fluid to cause the reservoir level to drop well below the fill mark. This allows the fluid in the lines to return to the reservoir without overflowing when you retract the caliper pistons for the new pads.

• During inspection, the flexible brake hose will need to be supported because it is still attached to the caliper. The easiest way to do this is by fastening a length of wire around the caliper and attaching it to a suspension component.
• Do not let the caliper hang unsupported because you may damage the flexible brake hose.

Part 2: Step-by-step instruction

1. Remove brake fluid
   Before you raise the vehicle, you will need to remove some of the brake fluid from the master cylinder to allow for fluid return into the master cylinder reservoir when you install the new brake pads. Using a siphon, remove enough fluid so that the reservoir level is well below the fill mark.
2. Raise the vehicle and remove wheel assembly
   Raise the vehicle to a comfortable working height. Remove the wheel assembly.
3. Inspect the brake assembly
   Check for any signs of fluid leaks or grease leakage from the hub seal. Check for any signs of a cracked or damaged rotor. Inspect the brake lines to see if there are any signs of leakage or deterioration of the flexible hoses.
4. Remove the brake pads
   Loosen and remove the caliper location pins or bolts. Lift and rotate the caliper away from the rotor. Ensure that the caliper is not hanging unsupported. Secure and support the caliper by fastening a length of wire around it and attaching it to a suspension component. Remove the worn brake pads from the caliper by pulling them from their guide locations. It is good practice to lightly skim the rotors when new pads are to be installed, so arrange with your supervisor to have the rotor machined. Carry out a run out test with a dial gauge in addition to measuring rotor thickness with an outside micrometer. This will determine the amount of material to be skimmed. Mount the dial gauge fixture to a fixed point in relation to the rotor, so that when the rotor is turned it shows how much run out variation there is in the disc. Check the amount of run-out against the manufacturers specifications and report any excessive tolerances in your findings to your supervisor .
5. Check the slide or locating pins
   Check the locator pins, sleeves, and insulators for any signs of wear or binding. With the sliding caliper type, ensure the caliper can slide freely on the runners.
6. Retract the piston
   To fit new pads, you will need to retract the caliper piston back into its housing. One of the most common methods is to fit a block of wood and a ‘C’ or ‘G’ clamp over the piston. Tighten the clamp to retract the piston back into the housing. As the piston moves back, it will displace brake fluid back into the master cylinder reservoir. Remove the block of wood and clamp after the piston has been retracted.
7. Install the new brake pads
   Compare the new brake pads to the originals to confirm that they are the correct pads to install. The backing plates should be exactly the same shape. Install the new pads into the caliper. Slide the caliper assembly onto the rotor, and align the mounting or locating pins. Refer to the shop manual for the correct procedure and specifications for installing the pins or bolts. Install the pins or bolts and secure them in place. Torque the bolts or retainers to the correct specification.
8. Check/remove brake system air and refit wheels
   Using the correct procedure bleed the brakes and refit the wheel assemblies.