How to Replace,

BRAKE PADS, LININGS & FLUID

This workshop procedure guide contains: Step-by-step instructions on how to replace brake pads, linings and fluid.

Personal safety: Whenever you perform a task you must use personal protective clothing and equipment that is appropriate for the task. Among other items, this may include: • Work clothing, such as overalls 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.

TIPS FOR REPLACING BRAKE PADS 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.

Replacing Brake Pads 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 disc.

Inspect the brake lines to see if there is any sign 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 disc.

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 out brake pads from the caliper by pulling them from their guide locations.

It is good practice to lightly skim the discs when new pads are to be installed.

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 disc...

...and align the mounting or locating pins.

Refer to the 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.

TIPS FOR REPLACING BRAKE LININGS Objective: Remove and replace drum brake linings.

Safety check: •

Never use any petroleum or mineral based products, such as gasoline, kerosene etc, to clean a braking system or its components. Doing so can result in a failure of the braking system and its components. This may result in serious damage to the vehicle.

Points to note: • • • •

Linings are designed to withstand extreme heat generated during braking. The linings must be able to withstand these temperatures and still maintain their braking efficiency. Oil or grease contaminants on the lining can have an adverse effect on the co-efficient of friction of the linings. If you need to bleed your brakes, you may need to replace your brake fluid. If you are bleeding brakes on an older vehicle, or you don’t know the vehicle’s service history, it is good practice not to fully depress the brake pedal during bleeding.

Replacing Brake Linings

1. Prepare the vehicle

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 be below the fill mark. This allows for a fluid expansion when you retract the wheel cylinder pistons for the new linings.

Raise the vehicle using the correct procedure to a comfortable working height and remove the wheel assembly.

2. Remove and inspect the brake drum

Remove the brake drum taking care to remove any locating screws and back off any manual adjusters.

Check for any signs of fluid leaks or grease leakage from a hub or axle shaft seal.

Check the brake drum for any cracks or other damage.

3. Inspect the brake lines

Inspect the brake lines to see if there are any signs of leakage or deterioration of flexible and/or steel hoses.

4. Remove the brake shoes and linings

Install a brake cylinder clamp onto the wheel cylinder. This will prevent the piston coming out when you release the brake shoes.

Check the manual for the correct service tools required to release the springs and clips.

Using the correct tool, release the retaining clips and disconnect the return springs.

Remove the worn brake shoes and their linings from the backing plate.

5. Check retaining clips and return springs

Check the condition of the return springs making sure they have no spread coils that will reduce their efficiency.

Check that the retaining clips are not damaged and will keep the brake shoes in position.

6. Install the new brake shoes

Compare the new brake shoes and their linings to the original ones to make sure they are the correct replacements.

Referring to the manual, install the brake shoes onto the backing plate.

Install the return springs and retaining clips in accordance with the manufacturers’ specification and direction.

7. Refit the brake drum

As the return spring tension takes effect, the wheel cylinder piston should move back into the cylinder. If it doesn’t you may have to manually retract the piston.

Now refit the brake drum. Prepare the cylinder for bleeding using a clear bleeder hose and a jar with a small amount of brake fluid in the base.

Open the bleeder screw and have someone to assist you by slowly pushing the brake pedal down and observe the air bubbles coming out.

Close the bleeder screw off, and have the assistant slowly release the pedal. Repeat procedure as necessary to remove all air.

Manually adjust the brakes if necessary to ensure that the drum rotates without binding.

Refit the wheel and tyre assembly using the correct procedure. Repeat this process for each of the other drum brake assemblies.

8. Bleed system if required and test

If at the completion of the replacement process the brake pedal feels “spongy”, you should bleed the system of air from all of the brake assemblies.

Using the correct procedure to do this, and at the completion of the job, you should recheck the system to ensure that a firm pedal is achieved...

...and that the wheels cannot be rotated when the brake pedal is applied.

TIPS FOR REPLACING BRAKE FLUID Objective: Test and replace brake fluid.

Safety check: • • • • •

Never use any petroleum or mineral based products, such as gasoline, kerosene etc, to clean a braking system or its components. They are not compatible and will result in a failure of the braking system and its components. This may result in injury to the passengers or damage to the vehicle. If brake fluid splashes into your eyes, rinse it out with tap water immediately. Do not swallow brake fluid. It is toxic. Make sure that when you are bleeding the brakes, you do not empty the brake fluid reservoir or you will cause internal damage to the master cylinder. 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: • • • • • •

Brake fluid can damage the paintwork by softening the base paint. Brake fluid has a hygroscopic nature; it will absorb moisture rapidly. As moisture is absorbed, the boiling point is lowered. This can cause the phenomenon known as ‘brake fade’. Always replace the reservoir cover or lid as soon as possible. Do not use brake fluid that has been left in an open container. Brake fluid types are identified by their D.O.T. number. The higher the D.O.T. number, the higher its boiling point.

• Most vehicles use either D.O.T. 3 or D.O.T. 4 fluid. These fluids are both glycol-based but differ in specifications. The reservoir cover or cap will usually state the type of fluid to be used. • A D.O.T. 5 is synthetic fluid and normally referred to as ‘silicone’ brake fluid; it’s usually colored purple for easy identification and it’s not recommended for vehicles fitted with ABS. • Do not mix D.O.T. 5 brake fluid with a D.O.T. 3 or 4 glycol-based fluids. They are incompatible. • The majority of today’s braking systems use a combination of dissimilar metals. Manufacturers use aluminium in pistons and housings, steel in some wheel cylinders and brake lines. • When moisture mixes with brake fluid a galvanic action can occur. Galvanic action is similar to the operation of a battery. The more moisture in brake fluid, the higher the galvanic reading and the greater the corrosion it causes. • If you need to bleed your brakes, you may need to replace your brake fluid. • When bleeding the brakes, it will be necessary to top up the brake fluid after bleeding each brake station. • Most manufacturers recommend that brake fluid be changed at least every two years. Consult your owner’s manual for the specified intervals for the model you are working on and the type of replacement brake fluid recommended. • There are a number of different brake bleeding methods. Some repair shops will use a ‘pressure bleeder’ while others may have a ‘vacuum brake bleeder’. Manual bleeding is discussed in this procedure. • Manufacturers recommend that when bleeding brakes; push the brake pedal to the floor. If you are changing brake fluid on an older vehicle, or if you are uncertain of the vehicle’s service history, it is wise to depress the pedal through its normal range of movement. This will prevent the components in the master cylinder from coming into contact with contaminants. • Brake assemblies, either disc or drum, are often referred to as braking stations.

Replacing Brake Fluid 1. Check for galvanic reaction

Remove the brake fluid reservoir cap...

...and set the multimeter to read voltage on the lowest voltage range of the meter.

Place one of the multimeter probes into the brake fluid...

...and the other against the body of the master cylinder.

The voltage should be no greater than 0.3 volts.

If the voltage is higher, this indicates a galvanic reaction, and means that there is an unacceptable level of moisture in the brake fluid.

2. Remove the excess brake fluid

Use an old hydrometer or similar device...

...to suck out the contaminated fluid from the master cylinder reservoir.

Place the discarded brake fluid into a container that can be disposed of in an environmentally friendly manner.

3. Top up with new fluid

Top up the master cylinder reservoir with clean fluid...

...until it reaches the “FULL” line.

Close the brake fluid container as quickly as possible to prevent contamination and evaporation of the fluid.

4. Manually bleed the brake system

Open the bleeder screw that is the furthest from the master cylinder and ask an assistant to slowly push the brake pedal down.

With a clear bleeder hose inserted into a jar, you can observe the air bubbles coming out.

Close the bleeder screw off...

...and have the assistant slowly release the pedal.

Continue this process until there are no more air bubbles coming out of the brake station and the new brake fluid is present.

Close off the bleeder screw and tighten it to the manufacturers specifications.

Repeat this procedure for each of the other brake stations, starting from the farthest and moving closer to the master cylinder.

5. Inspect and test

Inspect each of the brake stations to ensure that there are no leaks and the bleeder screws are closed correctly.

A simple way of doing this is to ask the assistant in the vehicle to place their foot on the brake pedal, as if they were applying the brakes when driving the vehicle normally.

Now you can check all the bleed points and hose connections for leaks while the assistant is maintaining the pressure on the system...

...and thus any fluid that could be leaking as a result of a loose joint in the components.

After you are satisfied that it is all correct, lower the vehicle.

Carry out a final check for any leaks around the master cylinder or brake stations.

Replace the master cylinder cover and check to see that it is fully seated.

Dilute any brake fluid that may have been spilt with fresh clean water.

Check the brake system pedal pressure, fluid levels, and visual signs of leaks.

When you are satisfied, the vehicle should be road tested to ensure the integrity of the braking system.

Disclaimer:

The material contained in our brochure is provided for general information purposes and does not constitute professional advice. Subject to all applicable law MIDAS will not be held responsible for loss or damage, which may arise from reliance of the information contained in this brochure.

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