Brake Proportioning Valve

Replace the brake proportioning valve on a 2008 Dodge Viper, which regulates hydraulic pressure between front and rear brake circuits for proper brake balance.

Warnings

Tools required

Parts

• Brake proportioning valve assembly × 1 — Use OEM specification
• Brake line sealing washers/crush washers (if applicable) × 4 — Use OEM specification

Fluids

• DOT 4 brake fluid — 1 qt

Preparation

1. Park vehicle on level, solid ground and apply parking brake firmly
2. Place wheel chocks behind front wheels
3. Ensure engine is cool to the touch before beginning work
4. Open the hood and locate the brake fluid reservoir on the master cylinder
5. Use a turkey baster or fluid extractor to remove brake fluid from the reservoir to prevent overflow during the procedure (dispose of old fluid properly)
6. Gather all tools, parts, and a full bottle of fresh DOT 4 brake fluid before beginning

Procedure

1. 1

   Raise and support the vehicle
   Raise the rear of the vehicle using a jack at an approved lift point. Support securely on jack stands rated for the vehicle weight. The proportioning valve is typically mounted on the frame rail or rear axle area. Ensure you have adequate clearance to work underneath the vehicle safely. Never work under a vehicle supported only by a jack.
2. 2

   Locate the brake proportioning valve
   Locate the proportioning valve assembly per factory service documentation for this specific vehicle. The mounting location (frame rail near rear axle vs. near the master cylinder) and the exact number/routing of brake lines must be confirmed against the FSM before proceeding. Visually inspect the valve and all connected brake lines for damage, corrosion, or leaks. damage, corrosion, or leaks.
3. 3

   Clean the work area and connections
   Use a wire brush and brake cleaner to thoroughly clean around all brake line connections at the proportioning valve. Remove any dirt, rust, or debris that could contaminate the brake system when lines are disconnected. This step is critical to prevent introducing contaminants into the hydraulic system.
4. 4

   Label and disconnect the brake lines
   Before disconnecting any lines, use masking tape or a marker to label each brake line connection (inlet, left rear outlet, right rear outlet, front circuit outlet) to ensure correct reinstallation. Position a drain pan under the valve to catch brake fluid. Using a flare nut wrench to prevent rounding the fittings, carefully loosen and disconnect the 4 brake lines from the proportioning valve. Immediately plug or cap each brake line end and valve port with brake line plugs to minimize fluid loss and prevent contamination. Expect some brake fluid spillage. Note: Brake line flare nut fitting size to be verified against factory service documentation
5. 5

   Remove the proportioning valve mounting fasteners
   Locate the mounting bracket or fasteners securing the proportioning valve to the frame rail. Remove the mounting fasteners (count and type per factory service documentation) and carefully remove the old proportioning valve from the vehicle. Inspect the mounting location for corrosion or damage.
6. 6

   Prepare and install the new proportioning valve
   Remove the new proportioning valve from its packaging and inspect it for damage. If the valve includes port plugs, remove them. If your application uses crush washers or sealing washers at the brake line connections, install new washers on each port of the new valve. Position the new proportioning valve in the mounting location, aligning it with the mounting holes. Install and hand-tighten the mounting fasteners, but do not fully tighten yet to allow slight adjustment for brake line alignment.
7. 7

   Reconnect the brake lines
   Remove the plugs from the brake lines and the new valve ports. Carefully thread each brake line into its corresponding port on the new proportioning valve, following your labels from step 4. Start each fitting by hand to ensure proper thread engagement and prevent cross-threading. Once all four lines are hand-started, use a flare nut wrench to tighten each connection securely. Tighten in a crisscross pattern to ensure even seating. Do not overtighten, as this can damage the flare fittings or crack the valve body. Note: Brake line fitting torque per factory service documentation
8. 8

   Secure the valve mounting
   With all brake lines connected and properly aligned, fully tighten the proportioning valve mounting fasteners to secure the valve to the frame rail. Verify that no brake lines are kinked, twisted, or under tension. Note: Mounting bolt torque per factory service documentation
9. 9

   Refill the brake fluid reservoir
   Lower the vehicle or maintain it on jack stands as preferred for the bleeding process. Go to the brake fluid reservoir at the master cylinder and fill it to the MAX line with fresh brake fluid of the grade specified on the reservoir cap / in the factory service manual (verify DOT 3 vs DOT 4) from a sealed container. Keep the reservoir filled throughout the bleeding process to prevent introducing air into the master cylinder.
10. 10

    Bleed the brake system completely
    The entire brake system must now be bled to remove all air introduced during valve replacement. Bleed the brakes in the sequence specified by the factory service manual for this vehicle. NOTE: This vehicle is ABS-equipped; a scan-tool-assisted ABS bleed procedure may be required to fully purge air from the ABS/EBD hydraulic unit. Verify the correct wheel sequence and whether a scan tool bleed is needed before proceeding. At each wheel, attach a clear hose to the bleeder screw, submerge the other end in a container of clean brake fluid, and have an assistant pump the brake pedal 3-4 times and hold pressure. Open the bleeder screw to release fluid and air, then close it before the pedal reaches the floor. Repeat until no air bubbles appear in the discharged fluid. Alternatively, use a pressure bleeder following the manufacturer's instructions. Check and refill the master cylinder reservoir frequently during bleeding.
11. 11

    Inspect for leaks
    With the system bled and the reservoir filled to the proper level, carefully inspect all four connections at the new proportioning valve for any signs of brake fluid leakage. Wipe the connections dry with a clean shop towel, then have an assistant apply firm, steady pressure to the brake pedal while you observe each connection. Any leakage requires immediate correction by retightening the fitting or replacing damaged components.
12. 12

    Test brake pedal feel and function
    With the vehicle still safely supported and not in gear, pump the brake pedal multiple times. The pedal should feel firm and consistent, with no sponginess or excessive travel. If the pedal feels soft or goes to the floor, air remains in the system and further bleeding is required. Do not proceed until pedal feel is firm and normal.

Reassembly

1. Lower the vehicle from jack stands once all testing is complete
2. Perform a final visual inspection of the proportioning valve installation and all brake line connections
3. Top off the brake fluid reservoir to the MAX line with fresh DOT 4 fluid
4. Clean any brake fluid residue from the chassis and components with water

Verification

• Before driving, start the vehicle and pump the brake pedal multiple times with the engine running to verify power brake assist is functioning and pedal feel remains firm
• Perform initial test stops at very low speed (under 10 mph) in a safe, traffic-free area to verify brake function
• Gradually increase speed and test brake response, checking for proper operation, unusual noises, or pulling to one side
• After initial test drive, re-inspect all brake line connections at the proportioning valve for any signs of leakage
• Monitor brake pedal feel and brake fluid level over the next several days of driving
• If any abnormality is detected (soft pedal, pulling, noise, warning lights), immediately stop driving and have the system inspected by a professional

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