Brake Proportioning Valve

This procedure covers the removal and replacement of the brake proportioning valve on the 2025 Rivian EDV 500, which controls hydraulic pressure distribution between front and rear brakes in this dual-motor electric delivery vehicle.

Warnings

Tools required

Parts

• Brake proportioning valve assembly × 1 — Use OEM Rivian specification
• Brake line sealing washers × 4 — Use OEM specification
• Brake line protective caps × 4 — Generic brake line caps

Fluids

• DOT 4 Brake Fluid — 2 qt

Preparation

1. Park vehicle on level ground and engage parking brake firmly
2. Place wheel chocks at front wheels
3. Open driver's door and keep it open throughout the procedure to prevent electronic lock-out
4. Put on nitrile gloves and safety glasses
5. Ensure adequate ventilation in work area for brake fluid vapors
6. Gather all tools, replacement parts, and fresh DOT 4 brake fluid
7. Photograph brake line routing and valve orientation before disassembly
8. Have fire extinguisher rated for electrical fires nearby as a precaution

Procedure

1. 1

   Disable vehicle power systems
   Access the vehicle power menu through the center display screen. Select 'Service Mode' and disable the vehicle power systems. Wait 5 minutes for capacitors to discharge. Verify the instrument cluster is completely dark. Do NOT disconnect the 12V battery as this will lock electronic systems.
2. 2

   Access cargo area and remove trim panels
   Enter the cargo area from the rear doors. Locate the left side interior trim panel near the rear wheelwell. Use trim removal tools to carefully release the clips securing the lower trim panel. Remove the panel to expose the frame rail area where the proportioning valve is mounted. Set trim panels aside safely to avoid damage.
3. 3

   Locate and inspect the brake proportioning valve
   The proportioning valve is mounted on the left frame rail, approximately 18 inches forward of the rear axle centerline. It has four brake lines connected: two from the master cylinder (front and rear circuits) and two outputs to the wheel circuits. Visually inspect the valve and lines for existing leaks, corrosion, or damage. Take detailed photos of the line routing and orientation.
4. 4

   Prepare for brake fluid loss
   Position a large brake fluid catch pan beneath the proportioning valve area. Place absorbent shop towels around the valve to catch any dripping fluid. Have additional rags ready. Note that approximately 1-2 quarts of fluid may drain from the lines when disconnected.
5. 5

   Disconnect brake line 1 (master cylinder input - front circuit)
   Using the appropriate size flare nut wrench, carefully loosen the front circuit brake line fitting at the proportioning valve inlet. Turn counterclockwise slowly. Once loose, quickly thread on a protective cap to minimize fluid loss. Be prepared for fluid to drain. Secure the line away from the work area with mechanic's wire to prevent contamination.
   ⚠Use only flare nut wrenches on brake line fittings. Standard wrenches will round off the soft brass fittings, making removal impossible without cutting lines.
6. 6

   Disconnect remaining three brake lines
   Working methodically, disconnect the remaining three brake lines in this order: rear circuit input from master cylinder, front circuit output to wheels, rear circuit output to wheels. Cap each line immediately after disconnection. Label each line with tape or wire tags if not already clearly identifiable to ensure correct reconnection.
7. 7

   Remove proportioning valve mounting hardware
   Locate the two mounting bolts securing the proportioning valve to the frame bracket. Using a socket wrench, remove both mounting bolts while supporting the valve body with your other hand. The valve may have accumulated road grime; brake cleaner may be needed to access fasteners. Carefully remove the valve assembly from the vehicle.
8. 8

   Inspect brake lines and fittings
   With the valve removed, closely inspect all four brake line ends for damage, corrosion, or deformation. Check the threads inside each fitting for cross-threading or damage. Clean the exterior of the line ends with brake cleaner and a clean rag. Replace any damaged lines before proceeding. Inspect the frame mounting location for rust or damage.
9. 9

   Prepare new proportioning valve
   Unpack the new proportioning valve. Verify it matches the original valve exactly in port configuration and mounting pattern. Install new sealing washers on all four ports of the new valve. Do not reuse old washers as they will leak. Apply a small amount of clean DOT 4 brake fluid to the threads of each port to aid installation and prevent galling.
10. 10

    Install new proportioning valve
    Position the new proportioning valve into the frame mounting bracket, ensuring correct orientation matches your reference photos. Install both mounting bolts finger-tight. Torque mounting bolts evenly to manufacturer specifications if available; otherwise, torque to 18-22 ft-lbs. Do not overtighten as this can crack the valve body.
11. 11

    Reconnect brake lines to new valve
    Remove protective caps from brake lines. Working carefully, thread each brake line into its correct port on the new valve. Start each fitting by hand to ensure proper threading and avoid cross-threading. Once hand-tight, use the flare nut wrench to snug each fitting. Tighten fittings to 12-15 ft-lbs if using a torque wrench, or approximately 1/4 turn past snug by hand. Do not overtighten.
    ⚠Cross-threading brake line fittings will cause dangerous leaks. If a fitting does not thread easily by hand, stop and investigate. Never force fittings.
12. 12

    Verify all connections
    Visually inspect all four brake line connections at the proportioning valve. Each should be properly seated with no visible gaps. Verify all sealing washers are in place. Check that no brake lines are kinked, stretched, or touching hot components or sharp edges. Compare line routing to your reference photos.
13. 13

    Bleed the brake system
    Using a pressure bleeder connected to the brake fluid reservoir, bleed the entire brake system starting with the wheel farthest from the master cylinder (typically right rear), then left rear, right front, and left front. At each wheel, open the bleeder valve and allow fluid to flow until no air bubbles are visible and fluid runs clear. Close bleeder before releasing pressure. Repeat the full sequence twice to ensure complete air removal. Maintain reservoir level above MIN at all times during bleeding.
    ⚠️Air in the brake system will cause brake failure. Bleeding must be thorough and complete. If you are unsure about proper bleeding technique, stop and seek professional service.
14. 14

    Test brake pedal feel
    With the vehicle still off and in park, firmly press the brake pedal multiple times. The pedal should feel firm and not sink to the floor. If the pedal feels spongy or sinks, air remains in the system and additional bleeding is required. Continue bleeding until pedal feel is firm and consistent.
15. 15

    Inspect for leaks
    With the vehicle still in Service Mode, carefully inspect all four brake line connections at the proportioning valve for any signs of fluid seepage. Look for wet spots, drips, or fluid accumulation. Have an assistant press the brake pedal firmly while you observe connections under pressure. Any leak, no matter how small, must be corrected before proceeding.

Reassembly

1. Reinstall the cargo area interior trim panels, ensuring all clips are properly seated
2. Clean any brake fluid residue from the frame and surrounding areas with water and brake cleaner
3. Fill the brake fluid reservoir to the MAX line with fresh DOT 4 brake fluid
4. Exit Service Mode through the center display to restore normal vehicle operation
5. Close all doors and verify the vehicle systems power up normally

Verification

• Before moving the vehicle, perform a stationary brake test: Start the vehicle and press the brake pedal firmly. It should feel solid with no sponginess or excessive travel
• Check the instrument cluster for any brake system warning lights. If any brake warnings are illuminated, do NOT drive the vehicle
• Perform a low-speed brake test in a safe area: Drive the vehicle forward at 5 mph and apply brakes gently. The vehicle should stop smoothly with no pulling to either side
• Gradually increase test speed to 15 mph, then 25 mph, testing braking performance at each increment in a safe area free of traffic
• Return to the work area and re-inspect all brake line connections at the proportioning valve for any signs of leakage
• Check brake fluid level in reservoir - it should remain at MAX with no significant drop
• Test regenerative braking function (if equipped) integrates properly with hydraulic brakes
• If any abnormalities are detected (pulling, noise, vibration, warning lights, leaks, or soft pedal), do NOT drive the vehicle and seek immediate professional service
• Consider having a professional brake system inspection performed as a final verification given the safety-critical nature of this repair

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