Drum Brake System: Diagnosis Chevrolet Sonic I

Brake Drum Surface and Wear Inspection

Special Tools

CH-8001 Dial Indicator Set

For equivalent regional tools, refer to Special Tools .

1. With the brake drum removed, clean the brake shoe lining contact surface of the brake drum with denatured alcohol or an equivalent approved brake cleaner.
2. Inspect the braking surface of the brake drum for the following braking surface conditions: Heavy rust and/or pitting Light surface rust can be removed with an abrasive disc; heavy surface rust and/or pitting must be removed by refinishing the drum. Cracks and/or heat spots Excessive blueing discoloration Missing balance weights
3. If the braking surface of the brake drum exhibits one or more of the braking surface conditions listed, the drum requires refinishing or replacement.
4. Using a brake drum micrometer calibrated in thousandths-of-an-inch, measure and record any grooves present on the drum braking surface. Ensure that the measurements are only taken within the brake shoe lining contact area.
5. Compare the groove, or scoring depth recorded to the following specification: Specification Brake drum maximum allowable scoring: 0.50 mm (0.020 in)
6. If the brake drum scoring depth exceeds the specification, or if an excessive amount of scoring is present, the drum requires refinishing or replacement.
7. Mount the brake drum on a brake lathe.
8. Mount a dial indicator, CH-8001 indicator (1), or equivalent, and position the indicator button so it contacts the braking surface of the brake drum (2) at a 90 degree angle, approximately 19 mm (0.75 in) from the outer edge of the drum.
9. Measure and record the radial runout of the brake drum. Rotate the drum until the lowest reading is displayed on the indicator dial, then zero the dial. Rotate the drum until the highest reading is displayed on the dial.
10. Compare the radial runout of the brake drum to the following specification: Specification Brake drum maximum allowable radial runout: 0.03 mm (0.001 in)
11. If the brake drum radial runout exceeds the specification, the drum requires refinishing or replacement.

Drum Brake Hardware Inspection

1. Visually inspect the drum brake upper return spring (1) for the following conditions: Excessive corrosion Excessive stretching Broken Missing
2. If any of the conditions listed were found, the drum brake upper return spring requires replacement.
3. Visually inspect the park brake apply lever (2) for the following conditions: Bent Broken Missing
4. If any of the conditions listed were found, the park brake shoes require replacement.
5. Visually inspect the drum brake shoe hold down springs and cups (3) and pins for the following conditions: Excessive corrosion Broken Missing Bent pins
6. If any of the conditions listed were found, the hold down springs, cups, and pins require replacement.
7. Visually inspect the drum brake lower return spring (4) for the following conditions: Excessive corrosion Excessive stretching Broken Missing
8. If any of the conditions listed were found, the drum brake lower spring requires replacement.

Drum Brake Adjusting Hardware Inspection

1. Visually inspect the adjuster actuator spring (1) for the following conditions: Excessive stretching Excessive bending Excessive corrosion Broken Missing
2. If any of the conditions listed were found, the adjuster actuator spring requires replacement.
3. Visually inspect the adjuster actuator lever (2) for the following conditions: Bent Broken The lever engagement surface excessively worn Excessively bent or broken spring attachment tab Missing
4. If any of the conditions listed were found, the adjuster actuator lever requires replacement.
5. Visually inspect the adjuster assembly (3) for the following conditions: Bent Broken Seized adjuster wheel threads Excessively worn, damaged, or missing teeth
6. If any of the conditions listed were found, the adjuster assembly requires replacement.