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Thread: Servicing Drum Brakes

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    Vendor MotorCulture's Avatar
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    Jun 2009
    Sydney, Australia
    Mazda 3 SP23

    Servicing Drum Brakes

    Brakes are a critical safety system of a vehicle. The brake system should not be interfered with by anybody who does not have the appropriate skills and experience. Drum brake shoes should be replaced by a qualified mechanic.

    These are general instructions, for the assistance of experienced technicians. For more detailed instructions pertaining to a specific vehicle, consult the manufacturer’s service manual.

    Approved safety equipment should be used at all times. Use the correct tools for each task. Before starting work, ensure these instructions have been read and understood completely.

    Removing Brake Shoes

    1. Locate the master cylinder of your vehicle in order to drain brake fluid from it. Remove about half the brake fluid from the master cylinder and put it into a sealed container. Dispose of it properly. Never reuse old brake fluid. Important: Brake fluid is corrosive so do not get it on your vehicles paint. If you do, wash it off (brake fluid is water soluble) with plenty of water.

    2.Raise the vehicle off the ground and remove the wheels. If a vehicle hoist is not available, ensure the wheels are chocked and the vehicle is supported by chassis stands on level ground. Do not work under a car supported only by a jack.

    3.Remove the cars wheels by first loosening the wheel nuts whilst the car is still firmly on the ground. If you attempt to crack the nuts when the car is in the air, it may be harder to do so as the tyres have no resistance and will spin freely.

    4.To remove the brake drum from the hub, locate the round clip on the wheel studs. Remove using wire cutters or pliers. These are not reused and are there to keep the brake drum from falling off during the manufacturing process. The drum should now come off easily. If the brake shoes are dragging on the drum lining unwind the adjustment screw to ease the resistance from the brake shoes. If the brake drum cannot be removed with minimal force it may be rusted, use some rust release/penetrant spray and lightly tap the drum mount surface with a hammer.

    5.Examine the springs and components of the braking system. Take a picture for later reference in case you cannot remember how things go back together. Also examine the drum for uneven surface wear and cracks.

    6.Drums should be machined if they are to be re-used. There is a minimum thickness for each vehicle. If a drum is under minimum thickness (or will be under minimum thickness after machining replace the pair of drums.) Your local Auto part or Mechanic shop will are usually able to offer this service.

    7.Clean the newly machined drum / new drum with Bendix Brake/Parts Cleaner & Degreaser. If the drum was removed from the vehicle, re-fit the rotor following the manufacturer’s instructions.

    Bendix Brake/Parts Cleaner & Degreaser. Click Here for more information

    8.Inspect the brake system for wet patches which may indicate a brake fluid leak. Clean the brake system with Bendix Brake/Parts Cleaner & Degreaser. Do not use compressed air, dry brushing, oil-based or petroleum-based solvents. Many brake parts contain fibres that, if inhaled, can cause serious injury.

    9.If your vehicle uses your drum brakes as a parking brake remove the brake cable.

    10.Remove the springs using brake spring pliers or spring removal tool, the springs will be under pressure and can be dangerous so do not attempt this step without the appropriate tools. The springs hold the brake shoes against the drum lining. The return springs must be taken off first, then locate and remove the hold down springs that are directly on the brake shoes.

    11.Depending on the make and model of your vehicle there may be other components holding the brake shoes onto the hub. Remove the adjustment screw and spring as well as any other remaining springs with care. You can then remove the brake shoes as a pair. Allow the shoes to collapse together to make removal of the adjuster spring easy. Some brake setups have a small and large shoe design, take note of which way they go for when installing the new shoes.

    Installing new Brake Shoes
    1.Compare the old shoes to the new shoes to make sure that they replacement shoes share the same design and mounting pattern as the shoes that where installed on the vehicle.

    Note: The brake shoes pictured above are not Bendix Brake Shoes and are used as an example only.

    2.Align the Brake Shoes against the backing plate making sure everything aligns properly. If everything aligns properly then you may re-install the adjustment spring and screw.

    3.Re-install all the springs using the picture as a reference took earlier in the appropriate order. Reattach the parking brake cable and the return springs.

    4.Compare your setup to the pictures to ensure everything is connected properly.

    5.Place your freshly machined or replacement drums onto the hubs making sure that the drums spin freely. Use the adjustment screw to ease off or apply more force to the drum linings.

    6.Flush and replace the brake fluid, unless service records show that it has been replaced within the last 12 months. Brake fluid should be flushed and replaced at least once every two years, as it absorbs water from the atmosphere which reduces its performance. Refer to the vehicle manufacturer’s recommendation for the correct specification of brake fluid.

    To avoid contamination of the brake fluid, clean the master cylinder reservoir with Bendix Brake/Parts Cleaner & Degreaser before opening. Always use fresh brake fluid such as Bendix High Performance Brake Fluid DOT3 & DOT4 from a sealed container. Add new brake fluid to the reservoir as required. Flush new brake fluid through the entire brake system, starting at the wheel furthest from the master cylinder. Collect the used brake fluid in a suitable container. Refer to local regulations for disposal of used brake fluid.

    Bendix High Performance Brake Fluid DOT3 & DOT4. Click Here for more information

    7.Bleed the brakes following the manufacturer’s recommended procedure, paying attention to the appropriate bleeding order.

    8.Apply the brakes several times to set the brake pads and pistons in position. Top up the brake fluid reservoir if necessary. If the brake pedal does not feel firm under foot, repeat step 7. Wipe drums down again with Bendix Brake/Parts Cleaner & Degreaser.

    9.Fit the wheels, lower the vehicle to the ground and tighten the wheel nuts to the manufacturer’s recommended torque.

    10.Lower vehicle and road test. Do not severely apply brakes immediately after installation of new brake linings or permanent damage may occur to linings and/or brake drums may become scored. Brakes must be used moderately during first several hundred miles of operation to ensure proper burnishing.

    11.The brake system should be inspected by a qualified mechanic at least once per year, or more often if the vehicle travels long distances or is subject to heavy duty conditions.

    Bendix offers brake pads to suit all driving styles and conditions. To check out the full range of brake pads Bendix has to offer please Click Here.

    Last edited by MotorCulture; 22-02-13 at 01:36 AM.
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