This procedure replaces the brake proportioning valve, which regulates hydraulic pressure distribution between front and rear brakes on 2015-2020 Ford F-150 3.5L EcoBoost RWD models.

Warnings

Tools required

Parts

• Brake proportioning valve assembly × 1 — Use OEM Ford specification BC3Z-2B091-A or equivalent
• Brake line sealing washers × 4 — Use OEM specification

Fluids

• Motorcraft DOT 4 LV Brake Fluid — 1 qt

Preparation

1. Park vehicle on level ground and apply parking brake firmly
2. Place wheel chocks behind rear wheels
3. Verify you have the correct replacement proportioning valve for your specific F-150 model year and brake configuration
4. Open a fresh, sealed container of Motorcraft DOT 4 LV brake fluid
5. Locate the proportioning valve on the driver side frame rail, approximately below the driver's door area
6. Clean the work area around the valve with brake parts cleaner to prevent contamination

Procedure

1. 1

   Prepare brake fluid reservoir
   Open the hood and locate the brake fluid reservoir on the driver side firewall. Using a turkey baster or fluid extraction tool, remove as much old brake fluid as possible from the reservoir to minimize spillage when disconnecting brake lines. Wipe the reservoir cap and surrounding area clean before proceeding.
   ⚠Do not allow brake fluid reservoir to run completely empty during this procedure or air will enter the ABS hydraulic control unit, requiring dealer-level scan tool bleeding procedures.
2. 2

   Access the proportioning valve
   Raise the driver side of the vehicle using a floor jack at the front jacking point. Secure with jack stands under the frame rail. The proportioning valve is mounted to the driver side frame rail with two mounting bolts. On some models, you may need to remove a plastic splash shield or wire harness clips for better access.
3. 3

   Label and disconnect brake lines
   The proportioning valve has four brake line connections: two inlet lines from the master cylinder and two outlet lines to the wheels. Take a photo or clearly label each line position (front inlet, rear inlet, front outlet, rear outlet) using masking tape and marker. Position the drain pan under the valve. Using the appropriate size flare nut wrench, carefully loosen each brake line fitting. Turn fittings counterclockwise while holding the valve body steady to prevent twisting.
   ⚠️Use only a flare nut wrench on brake line fittings. Standard wrenches will round off the soft brass fittings and cause leaks.
   ⚠Brake fluid will drain from the lines. Keep drain pan positioned and have rags ready to catch fluid.
4. 4

   Remove proportioning valve mounting bolts
   Once all four brake lines are disconnected and moved aside, remove the two mounting bolts securing the proportioning valve to the frame rail bracket. The valve assembly can now be removed. Allow any remaining brake fluid to drain into the pan.
   ℹ️Note the orientation of the valve for proper installation of the replacement unit.
   Torque spec

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

   Inspect brake lines and clean mounting area
   Inspect all four brake line ends for damage, cracks, or excessive corrosion. Check that the flare seats are clean and undamaged. Wire brush the mounting bracket on the frame rail to remove any rust or debris. Wipe clean with brake parts cleaner.
6. 6

   Install new proportioning valve
   Position the new proportioning valve onto the frame rail mounting bracket in the same orientation as the original. Install the two mounting bolts finger-tight first to ensure proper alignment. Once confirmed, torque the mounting bolts to specification in an alternating pattern.
   ⚠Verify the valve orientation matches the original installation. Incorrect orientation will result in improper brake pressure distribution.
   Torque spec

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

   Connect brake lines to valve
   Install new sealing washers on each brake line fitting. Thread each brake line into its correct port on the proportioning valve hand-tight first, ensuring threads engage smoothly without cross-threading. Verify each line is connected to the correct port using your labels or photo. Once all four lines are hand-tight, use the flare nut wrench to tighten each fitting to specification. Follow the sequence if specified in your service manual, typically tightening outlet lines first, then inlet lines.
   ⚠️Cross-threaded or improperly torqued brake line fittings will leak and cause brake failure. Ensure fittings thread smoothly by hand before using wrench.
   Torque spec

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

   Refill brake fluid reservoir
   Lower the vehicle from jack stands. Go to the brake fluid reservoir under the hood and fill it to the MAX line with fresh Motorcraft DOT 4 LV brake fluid. Keep the reservoir topped off throughout the bleeding process.
9. 9

   Bleed brake system
   Bleed the brake system in the correct sequence: right rear, left rear, right front, left front. At each wheel, attach clear plastic tubing to the bleeder screw with the other end submerged in a container of clean brake fluid. Have an assistant pump the brake pedal 3-4 times and hold pressure. Open the bleeder screw 1/2 turn, allow fluid and air to escape, then close the bleeder before the pedal reaches the floor. Repeat until no air bubbles appear in the tubing. Torque each bleeder screw to specification after bleeding that wheel. Check and refill the reservoir frequently to prevent it from running dry.
   ⚠️Never allow the brake fluid reservoir to run empty during bleeding or air will enter the ABS system, requiring professional scan tool bleeding.
   ⚠If the brake pedal remains soft or spongy after bleeding all four wheels, the ABS hydraulic control unit may contain air and require dealer-level scan tool bleeding procedures.
   Torque spec

   Bleeder Screw16 Nm (12 lb-ft)
10. 10

    Inspect for leaks
    With the engine off, pump the brake pedal firmly 10-15 times to build pressure in the system. While holding firm pedal pressure, inspect all four brake line connections at the proportioning valve for any signs of brake fluid leakage. Wipe connections dry with a clean rag and observe for 30 seconds. No leakage should be present.
    ⚠️Any brake fluid leakage indicates a faulty connection or damaged component. DO NOT drive the vehicle until all leaks are corrected.

Reassembly

1. Reinstall any splash shields or wire harness clips that were removed for access
2. Final check: Ensure all brake line fittings are torqued to specification and show no signs of leakage
3. Ensure brake fluid reservoir is filled to MAX line with Motorcraft DOT 4 LV fluid
4. Dispose of old brake fluid properly at a recycling center or auto parts store

Verification

• With engine off, pump brake pedal firmly 5-10 times. Pedal should become firm and hold steady pressure without sinking
• Start the engine. Brake pedal may drop slightly as the brake booster engages, then should remain firm
• Perform a low-speed brake test in a safe area (empty parking lot). Vehicle should brake smoothly without pulling to one side
• Perform a firmer brake test from 25-30 mph. Braking should be smooth and controlled with no pulsation or pulling
• Re-inspect all brake line connections at the proportioning valve after test drive for any signs of leakage
• Check brake fluid reservoir level and top off if needed. Level should remain stable after bleeding is complete
• If brake pedal feels soft, spongy, or sinks under steady pressure, or if brake warning light illuminates, DO NOT drive the vehicle. Have it towed to a professional technician for diagnosis

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