Brake Proportioning Valve

This procedure covers the removal and replacement of the brake proportioning valve on a 2023 Chevrolet Bolt EUV, including brake fluid system drainage, valve replacement, and complete system bleeding.

Warnings

Tools required

Parts

• Brake proportioning valve assembly × 1 — Use OEM GM part number
• Brake line sealing washers (if equipped) × 4 — Use OEM specification

Fluids

• ACDelco DOT 4 Brake Fluid — 1 qt

Preparation

1. Park vehicle on level surface and apply parking brake firmly
2. Place wheel chocks behind rear wheels
3. Turn off vehicle and remove key from proximity
4. Open hood and locate 12V battery in engine compartment
5. Disconnect 12V negative battery terminal and isolate cable away from battery
6. Wait at least 2 minutes for airbag system capacitors to discharge
7. Locate brake master cylinder and proportioning valve assembly
8. Clean area around master cylinder and proportioning valve with brake cleaner to prevent contamination
9. Place absorbent pads or drip pan under work area to catch brake fluid
10. Have all new parts, tools, and fresh brake fluid ready before beginning

Procedure

1. 1

   Remove brake fluid from master cylinder reservoir
   Use a turkey baster, syringe, or fluid evacuation pump to remove as much brake fluid as possible from the master cylinder reservoir. This minimizes fluid loss and spillage during line disconnection. Dispose of old fluid properly. Do not allow reservoir to completely empty during subsequent steps.
2. 2

   Identify and label brake lines
   Locate the brake proportioning valve (typically mounted on or near the master cylinder). Identify all brake lines connected to the valve. Use tape or labels to mark each line's position (front left, front right, rear, etc.) to ensure correct reconnection. Take photographs for reference.
3. 3

   Disconnect brake lines from proportioning valve
   Using a flare nut wrench (NOT a standard wrench, which can round fittings), carefully loosen and remove each brake line fitting from the proportioning valve. Work slowly to avoid stripping the soft brass fittings. Have a catch container ready as fluid will drain from the lines. Cap or plug open lines immediately to prevent contamination and further fluid loss.
   ⚠Use only flare nut wrenches on brake line fittings. Standard wrenches will round the soft fittings and require line replacement.
4. 4

   Remove proportioning valve mounting bolts
   Locate the mounting bolts securing the proportioning valve to its bracket or the master cylinder. Remove the mounting bolts and carefully extract the valve assembly. Note the orientation and any spacers or washers for reinstallation. Inspect the old valve for signs of leakage or damage.
   Torque spec

   Proportioning Valve Bolts15 Nm (11 lb-ft)
5. 5

   Inspect mounting surfaces and prepare new valve
   Clean the mounting surface thoroughly with brake cleaner. Inspect for corrosion or damage. Verify the new proportioning valve matches the old unit exactly. Check that all ports are clear and protective caps are removed. Install any required sealing washers on the new valve ports.
6. 6

   Install new proportioning valve
   Position the new proportioning valve in the correct orientation matching the original installation. Thread mounting bolts by hand first to ensure proper alignment. Once all bolts are hand-started, torque to specification in a cross pattern if multiple bolts are present.
   ⚠Ensure valve orientation matches original installation. Incorrect orientation may affect brake system performance.
   Torque spec

   Proportioning Valve Bolts15 Nm (11 lb-ft)
7. 7

   Reconnect brake lines
   Thread each brake line fitting into the new proportioning valve by hand, referring to your labels and photos. Ensure fittings thread smoothly without cross-threading. Once all lines are hand-tight, use the flare nut wrench to torque each fitting to specification. Do not overtighten as this can damage the valve body.
   ⚠Do not overtighten brake line fittings. Overtightening can crack the valve body or strip fittings.
   Torque spec

   Brake Line Fittings15 Nm (11 lb-ft)
8. 8

   Refill master cylinder reservoir
   Fill the master cylinder reservoir with fresh ACDelco DOT 4 brake fluid from a sealed container to the MAX line. Keep the reservoir topped off throughout the bleeding process. Never allow the reservoir to run dry or air will enter the system.
9. 9

   Bleed brake system - rear brakes
   Begin bleeding at the wheel furthest from the master cylinder (typically right rear). Attach clear tubing to the bleeder screw and submerge the other end in a container with fresh brake fluid. Have an assistant pump the brake pedal 3-5 times and hold pressure. Open the bleeder screw while pedal is held, allow fluid to flow until stream is bubble-free, then close bleeder before pedal is released. Repeat until no air bubbles appear. Move to left rear and repeat. Check reservoir level frequently.
   ⚠️Never allow the master cylinder reservoir to run empty during bleeding or you will introduce air into the ABS system, requiring dealer-level scan tool bleeding.
   Torque spec

   Bleeder Screw14 Nm (10 lb-ft)
10. 10

    Bleed brake system - front brakes
    Continue bleeding process at right front wheel, then left front wheel, using the same procedure as rear brakes. Ensure all air is purged and only clean, bubble-free fluid emerges. The brake pedal should become progressively firmer as air is removed from the system.
    Torque spec

    Bleeder Screw14 Nm (10 lb-ft)
11. 11

    Perform final system check and ABS bleed if necessary
    With all wheels bled, check brake pedal feel. Pedal should be firm and not sink to the floor. If pedal remains spongy, air may be trapped in the ABS modulator. This requires a scan tool with brake bleeding function to cycle the ABS valves. If you do not have this capability, seek professional service to complete the ABS bleeding procedure.
    ⚠A spongy pedal after conventional bleeding indicates air in the ABS system. Professional scan tool bleeding is required.
12. 12

    Inspect for leaks and reconnect battery
    Thoroughly inspect all brake line connections at the proportioning valve for any signs of leakage. Wipe the area clean and look for fresh fluid. Check master cylinder reservoir level and top off to MAX line. Clean any spilled brake fluid from painted surfaces immediately. Reconnect the 12V negative battery terminal.

Reassembly

1. Ensure all brake line fittings are torqued to specification with flare nut wrench
2. Verify master cylinder reservoir is filled to MAX line with fresh DOT 4 fluid
3. Double-check all connections for tightness and absence of leaks
4. Clean any brake fluid residue from components and painted surfaces

Verification

• Start vehicle and verify no brake warning lights are illuminated on dash
• With engine running, pump brake pedal several times - pedal should be firm and consistent
• Check for leaks at all proportioning valve connections while assistant applies firm pedal pressure
• Perform a controlled brake test in a safe area at low speed (under 10 mph) to verify proper brake function
• Test brake response at progressively higher speeds in a safe, traffic-free area
• Verify equal braking force from all wheels - vehicle should stop straight without pulling
• Confirm brake pedal height and travel distance are normal compared to pre-repair operation
• If any abnormality is detected (spongy pedal, pulling, warning lights), DO NOT drive and seek professional diagnosis immediately

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