Wheel Cylinder

This procedure covers the removal and replacement of the rear wheel cylinder on a 2023 Chevrolet Bolt EUV, including brake system bleeding.

Warnings

Tools required

Parts

• Rear wheel cylinder assembly × 1 — Use OEM specification
• Brake shoe return springs (if damaged) × 1 — Use OEM specification
• Brake hardware kit (recommended) × 1 — Use OEM specification

Fluids

• ACDelco DOT 4 Brake Fluid — 0.5 qt

Preparation

1. Park vehicle on level surface and place wheel chocks at front wheels
2. Ensure vehicle is in Park mode and powered off completely
3. Release parking brake to allow rear brake drum removal
4. Loosen rear wheel lug nuts while vehicle is on ground
5. Raise rear of vehicle with floor jack and support securely on jack stands
6. Remove rear wheel completely
7. Clean brake drum and backing plate area with brake cleaner to prevent contamination

Procedure

1. 1

   Remove brake drum
   Remove the brake drum from the hub. If drum is stuck, thread two M8 bolts into the threaded holes on the drum face and tighten alternately to push drum off hub. Do not strike drum with hammer as this may damage bearings.
2. 2

   Document brake shoe assembly
   Before disassembling, take photos of brake shoe spring positions and hardware orientation for reference during reassembly. Note the position of upper and lower return springs, hold-down springs, and adjuster mechanism.
3. 3

   Remove brake shoes
   Using brake spring pliers, remove the upper and lower return springs from the brake shoes. Remove the hold-down springs and pins. Disconnect the parking brake cable from the lever. Remove both brake shoes and adjuster assembly as a unit. Set aside carefully to preserve spring positions.
   ⚠Brake springs are under tension and can cause injury if released suddenly. Control springs during removal.
4. 4

   Disconnect brake line from wheel cylinder
   Place a catch pan under the wheel cylinder. Using a line wrench, carefully loosen and disconnect the brake line fitting from the rear of the wheel cylinder. Immediately cap or plug the brake line to minimize fluid loss and prevent contamination. Allow residual fluid to drain into catch pan.
   ⚠Use a line wrench, not a standard wrench, to prevent rounding of the soft brass fitting.
5. 5

   Remove wheel cylinder mounting bolts
   Remove the two bolts securing the wheel cylinder to the brake backing plate. The wheel cylinder will now be free to remove. Inspect the backing plate mounting surface for corrosion or damage.
   Torque spec

   Mounting Bolts27 Nm (20 lb-ft)
6. 6

   Remove wheel cylinder
   Pull the wheel cylinder away from the backing plate and remove it completely. Inspect the backing plate bore for rust, corrosion, or damage. Clean the mounting surface with a wire brush and brake cleaner if necessary.
7. 7

   Install new wheel cylinder
   Position the new wheel cylinder onto the backing plate, aligning the mounting holes. Ensure the cylinder is fully seated against the backing plate. Install the mounting bolts finger-tight initially, then torque to specification.
   Torque spec

   Mounting Bolts27 Nm (20 lb-ft)
8. 8

   Reconnect brake line
   Remove the cap from the brake line. Thread the brake line fitting into the wheel cylinder by hand to ensure proper thread engagement. Using a line wrench, tighten the fitting to specification. Do not overtighten as this can strip the threads or damage the fitting.
   Torque spec

   Line Fittings20 Nm (15 lb-ft)
9. 9

   Reinstall brake shoes and hardware
   Referring to your photos, reinstall the brake shoe assembly with all springs and hardware in their original positions. Ensure the adjuster mechanism is properly positioned between the shoes and that the parking brake cable is reconnected to the lever. Verify all return springs and hold-down springs are correctly installed.
10. 10

    Install brake drum and wheel
    Clean the hub surface and inside of brake drum. Install the brake drum onto the hub, ensuring it seats completely. Install the wheel and thread lug nuts by hand. Lower vehicle slightly so tire contacts ground but vehicle weight is still on jack stands. Torque lug nuts to specification in a star pattern.
    Torque spec

    Wheel Lug Nuts190 Nm (140 lb-ft)
11. 11

    Bleed brake system
    With vehicle still supported on jack stands, bleed the brake system starting with the wheel cylinder just replaced. Attach clear tubing to the bleeder screw and submerge the other end in a container with clean DOT 4 brake fluid. Have an assistant pump the brake pedal 3-4 times and hold pressure. Open the bleeder screw briefly to release fluid and air, then close before pedal reaches floor. Repeat until fluid runs clear with no air bubbles. Tighten bleeder screw to specification. Check master cylinder level frequently and top off as needed.
    ⚠Never let the brake master cylinder run dry during bleeding or air will enter the system requiring complete system bleed.
    Torque spec

    Bleeder Screw10 Nm (7 lb-ft)
12. 12

    Complete brake bleeding sequence
    Bleed remaining wheels in this sequence: opposite rear wheel, right front, left front. This ensures complete air removal from the system. Top off brake fluid reservoir to MAX line with fresh ACDelco DOT 4 brake fluid when complete.

Reassembly

1. Lower vehicle completely from jack stands and remove jack
2. Perform final torque check on wheel lug nuts with vehicle on ground
3. Pump brake pedal several times until firm pedal is achieved before attempting to move vehicle
4. Check brake fluid level in master cylinder reservoir and top off if needed

Verification

• Verify brake pedal is firm and does not sink to floor when steady pressure is applied
• Check for any brake fluid leaks at wheel cylinder and brake line connection
• Test drive vehicle in safe area at low speed to verify proper brake operation
• Verify parking brake functions correctly and holds vehicle on incline
• Check that brake warning light is not illuminated on instrument cluster
• Recheck brake fluid level after test drive and top off if necessary
• Inspect wheel cylinder area again after test drive for any signs of leakage

Related trouble codes on this vehicle

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