Brake Caliper Rebuild - Rear

Complete rebuild of rear brake caliper including disassembly, cleaning, replacement of seals and hardware, reassembly, and bleeding on a 2023 Chevrolet Bolt EUV electric vehicle.

Warnings

Tools required

Parts

• Rear brake caliper rebuild kit (seals, boots, dust covers) × 1 — Use OEM specification
• Brake caliper slide pin hardware kit × 1 — Use OEM specification
• Copper crush washers for brake line × 2 — Use OEM specification

Fluids

• ACDelco DOT 4 Brake Fluid — 1 qt

Preparation

1. Park vehicle on level surface and engage parking brake
2. Disconnect 12V battery negative terminal to disable regenerative braking system
3. Using turkey baster or transfer pump, remove approximately half of brake fluid from master cylinder reservoir to prevent overflow during piston compression
4. Loosen rear wheel lug nuts while vehicle is on ground
5. Raise rear of vehicle and support securely with jack stands rated for vehicle weight
6. Remove rear wheel completely
7. Clean caliper exterior with brake parts cleaner to prevent contamination during disassembly

Procedure

1. 1

   Remove brake caliper from bracket
   Remove the caliper slide pin bolts from the rear of the caliper. Support the caliper with wire or bungee cord. Do not allow it to hang by the brake hose as this can damage the hose internally.
   Torque spec

   Caliper Slide Pin Bolts35 Nm (26 lb-ft)
2. 2

   Disconnect brake line from caliper
   Place drain pan under caliper. Using appropriate line wrench, loosen and remove the brake line fitting from the caliper. Immediately plug or cap the brake line to prevent fluid loss and contamination. Remove and discard copper crush washers. Fully remove caliper from vehicle and take to clean workbench.
   ⚠Use only a proper line wrench (flare nut wrench) to prevent rounding off the brake line fitting. A standard wrench will damage the fitting.
   Torque spec

   Line Fittings20 Nm (15 lb-ft)
3. 3

   Disassemble caliper and remove piston
   Remove caliper bleeder screw dust cap. In a controlled manner, use compressed air applied to the brake line port to carefully push the piston out of the caliper bore. Keep fingers clear of piston path. If compressed air is unavailable, use a brake caliper piston tool to rotate and extract the piston. Remove and discard piston seal and dust boot.
   ⚠️The piston can eject forcefully when using compressed air. Keep hands and face clear. Apply air pressure gradually and control piston movement with a rag.
   Torque spec

   Bleeder Screw10 Nm (7 lb-ft)
4. 4

   Clean and inspect caliper components
   Use pick to carefully remove the piston seal from the caliper bore groove. Remove dust boot retaining ring if equipped. Thoroughly clean the caliper bore, seal grooves, and all passages with brake parts cleaner and lint-free cloths. Inspect bore for scoring, pitting, or corrosion. Inspect piston for damage or excessive wear. Any significant damage requires caliper replacement, not rebuild.
   ⚠Do not use abrasive materials on caliper bore or piston surfaces. Even minor scratches can cause seal failure. If bore or piston shows damage, replace entire caliper.
5. 5

   Install new piston seal
   Lubricate the new piston seal from rebuild kit with clean DOT 4 brake fluid. Carefully install seal into the caliper bore groove, ensuring it seats completely and evenly around entire circumference. Verify seal is not twisted or pinched.
   ⚠Use only clean brake fluid or assembly lubricant from rebuild kit. Never use petroleum-based lubricants as they will destroy rubber seals.
6. 6

   Install piston and dust boot
   Lubricate new piston with clean DOT 4 brake fluid. Carefully install piston into caliper bore, ensuring it enters straight and does not damage seal. Push piston fully into bore or rotate while applying pressure if parking brake mechanism requires. Install new dust boot over piston and seat retaining ring or boot lip into caliper groove completely.
   ⚠Ensure piston enters bore perfectly straight. Cocking the piston can cut or dislodge the seal, causing immediate brake failure.
7. 7

   Service caliper slide pins
   Remove slide pins from caliper bracket if not already removed. Clean pins and bores thoroughly with brake parts cleaner. Inspect pins and rubber boots for wear, cracking, or damage. Replace if necessary. Apply thin coat of high-temperature silicone brake grease to slide pins and reinstall into bracket with new boots from hardware kit.
   ⚠Use only silicone brake grease on slide pins. Other lubricants can damage rubber components or contaminate brake pads.
8. 8

   Reconnect brake line to caliper
   Install new copper crush washers on both sides of brake line fitting. Position caliper and thread brake line fitting into caliper port by hand to prevent cross-threading. Using line wrench and torque wrench, tighten fitting to specification.
   ⚠New copper crush washers are mandatory. Reusing old washers will cause brake fluid leaks and potential brake failure.
   Torque spec

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

   Reinstall caliper to bracket
   Position caliper over brake rotor and align with slide pins on bracket. Apply medium-strength thread locker to caliper slide pin bolts. Install and torque slide pin bolts to specification using silicone brake grease on threads.
   ⚠️Proper torque on caliper mounting hardware is critical for brake function and safety. Use calibrated torque wrench.
   Torque spec

   Caliper Slide Pin Bolts35 Nm (26 lb-ft)
10. 10

    Bleed brake caliper
    Fill master cylinder reservoir to MAX line with fresh DOT 4 brake fluid. Attach bleeder hose to bleeder screw with clear tubing into clean container. Have assistant pump brake pedal 3-4 times and hold pressure, or use vacuum bleeder. Open bleeder screw 1/4 to 1/2 turn and allow fluid/air to evacuate. Close bleeder screw before pedal reaches floor. Repeat until fluid flows clear without air bubbles. Torque bleeder screw to specification.
    ⚠️Air in brake lines causes spongy pedal and reduced braking ability. Bleeding must be thorough and complete.
    Torque spec

    Bleeder Screw10 Nm (7 lb-ft)
11. 11

    Reinstall wheel and verify torque
    Clean wheel mounting surface and hub face. Install wheel and hand-tighten all lug nuts in star pattern. Lower vehicle until tire just contacts ground. Torque lug nuts to specification in star pattern. Fully lower vehicle and verify final torque.
    Torque spec

    Wheel Lug Nuts136 Nm (100 lb-ft)

Reassembly

1. Repeat entire procedure for opposite rear caliper to ensure balanced braking performance
2. Fill master cylinder reservoir to MAX line with fresh DOT 4 brake fluid
3. Pump brake pedal slowly until firm pedal feel returns (may require 20-30 pumps)
4. Reconnect 12V battery negative terminal
5. Check master cylinder fluid level again after pumping brakes

Verification

• With engine off (vehicle in READY mode for EV), pump brake pedal repeatedly - pedal should become firm and not sink to floor
• Start vehicle and verify brake pedal remains firm with no unusual softness or travel increase
• Inspect all brake line connections and caliper for any signs of fluid leakage
• Check master cylinder reservoir level - should be at MAX line
• Perform low-speed brake test in safe area - brakes should engage smoothly without pulling to either side
• Perform multiple brake applications from 15-20 mph to verify proper function and pedal feel
• After test drive, recheck all torque specifications on caliper bolts and wheel lug nuts
• Inspect for any fluid leaks around caliper and brake line connections after test drive
• Check brake fluid level in master cylinder reservoir one final time

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