Replace the brake proportioning valve, which controls hydraulic pressure distribution between front and rear brakes to prevent rear wheel lockup during braking.

Warnings

Tools required

Parts

• Brake proportioning valve assembly × 1 — Use OEM Toyota part number
• Brake line copper washers/gaskets (if equipped) × 1 — Typically included with valve

Fluids

• DOT 3 Brake Fluid — 1 qt

Preparation

1. Park vehicle on level, solid ground and set parking brake firmly
2. Place wheel chocks behind rear wheels
3. Open brake fluid reservoir and use turkey baster to remove old fluid to minimum level (prevents overflow during work)
4. Locate the proportioning valve assembly - typically mounted on or near the master cylinder in the engine bay
5. Spray brake line fittings at proportioning valve with penetrating oil and allow 15-30 minutes to soak
6. Prepare brake line plugs/caps and have ready to immediately seal open lines
7. Lay out clean rags and brake fluid catch pan under work area
8. Have fresh DOT 3 brake fluid ready - do not reuse old fluid

Procedure

1. 1

   Mark and photograph brake line connections
   Before disconnecting anything, take clear photographs of all brake line connections to the proportioning valve from multiple angles. Use a marker or tape to label each brake line with its position (front left, front right, rear, etc.). The valve typically has 4-5 ports depending on configuration. Accurate reinstallation is critical for proper brake function.
2. 2

   Disconnect brake lines from proportioning valve
   Using a flare nut wrench (NOT an open-end wrench), carefully loosen each brake line fitting at the proportioning valve. Work slowly to avoid rounding the soft brass fittings. Have a catch pan positioned underneath as brake fluid will drain. Once loosened, unthread fittings by hand and immediately plug each open brake line with brake line caps to prevent fluid loss and contamination. Also plug the ports on the old proportioning valve to minimize spillage.
   ⚠Flare nut wrenches are essential - standard open-end wrenches will round off brake line fittings. If a fitting begins to round, stop immediately and use a 6-point flare nut wrench.
3. 3

   Remove proportioning valve mounting hardware
   Remove the mounting bolts securing the proportioning valve to its bracket or master cylinder. The valve may be held by 1-3 bolts depending on design. Keep track of any spacers, washers, or rubber isolators. Carefully remove the old proportioning valve assembly, being careful not to spill remaining brake fluid.
   ⚠Support the valve as you remove the final mounting bolt to prevent it from dropping and damaging brake lines.
   Torque spec

   Proportioning Valve Bolts15 Nm (11 lb-ft)
4. 4

   Inspect brake lines and fittings
   With the valve removed, inspect all brake line ends for damage, cracks, or excessive corrosion. Check that the flared ends are smooth and not cracked. Inspect threads on fittings - they must be clean and undamaged. If any brake lines show damage, they must be replaced before proceeding. Clean the mounting area of any dirt or old brake fluid residue.
5. 5

   Prepare new proportioning valve
   Unbox the new proportioning valve and verify it matches the original valve in terms of port configuration and mounting. If the valve includes new copper sealing washers or gaskets for the brake line fittings, have these ready to install. Remove any protective caps or plugs from the new valve's ports just before installation.
6. 6

   Install new proportioning valve
   Position the new proportioning valve in the mounting location, ensuring any rubber isolators or spacers are properly positioned. Start all mounting bolts by hand to ensure proper alignment. Once all bolts are started, torque the proportioning valve mounting bolts to specification in a crossing pattern if multiple bolts are present.
   ℹ️If the service manual specifies a torque sequence for multiple mounting bolts, follow that sequence exactly. Otherwise, use a crossing pattern to ensure even mounting pressure.
   Torque spec

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

   Connect brake lines to new valve
   Remove plugs from brake lines and new valve ports. Install new copper washers if provided. Carefully thread each brake line fitting into the correct port on the new valve by hand, referring to your photographs and labels. Thread fittings at least 3-4 turns by hand to ensure they are not cross-threaded. Once all fittings are hand-tight, use the flare nut wrench to torque each brake line fitting to specification. Work methodically and verify each line is connected to the correct port.
   ⚠️Cross-threading brake line fittings will cause brake fluid leaks and brake failure. If a fitting does not thread smoothly by hand, remove it and try again - never force it with a wrench.
   ℹ️If the service manual specifies a tightening sequence for brake line fittings, follow that sequence exactly to ensure proper sealing.
   Torque spec

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

   Refill brake fluid reservoir
   Fill the brake fluid reservoir to the MAX line with fresh DOT 3 brake fluid. Keep the reservoir topped off throughout the bleeding process. Never allow the reservoir to run dry during bleeding as this will introduce air into the system.
   ⚠Use only fresh brake fluid from a sealed container. Brake fluid absorbs moisture from the air and contaminated fluid reduces braking performance.
9. 9

   Bleed brake system - initial bleeding
   The entire brake system must be bled to remove all air introduced during valve replacement. Begin bleeding at the wheel furthest from the master cylinder (typically right rear), then left rear, right front, and left front. At each wheel, attach clear tubing to the bleeder screw and submerge the other end in a container of brake fluid. Have an assistant pump the brake pedal 3-5 times and hold pressure. Open the bleeder screw 1/2 turn while the pedal is held - fluid and air will flow out. Close the bleeder before the assistant releases the pedal. Repeat until no air bubbles appear in the tubing. Torque bleeder screw to specification after bleeding each wheel.
   ⚠️Check and refill the brake fluid reservoir frequently during bleeding. If the reservoir runs dry, air will enter the system and you must start the bleeding process over.
   ⚠The assistant must NOT release the brake pedal while the bleeder screw is open, as this will draw air back into the system.
   Torque spec

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

    Inspect for leaks
    With the brake system bled, carefully inspect every connection at the proportioning valve for signs of brake fluid leakage. Wipe all fittings clean with a rag, then have an assistant firmly press the brake pedal and hold for 30 seconds while you watch for any fluid seepage. Check both the brake line fittings and the valve mounting bolts. If any leaks are found, release pressure, tighten the leaking fitting slightly (do not over-torque), and retest. If leaking persists, the connection must be disassembled and inspected for damage.
    ⚠️Any brake fluid leak, no matter how small, must be corrected before the vehicle is driven. Even minor leaks will worsen and can lead to complete brake failure.
11. 11

    Test brake pedal feel
    With the engine off, pump the brake pedal several times. The pedal should feel firm and not sink slowly to the floor. A spongy pedal indicates air still in the system - repeat bleeding procedure. A pedal that sinks slowly indicates a leak - recheck all connections. The pedal should travel no more than halfway to the floor with firm pressure applied.

Reassembly

1. Ensure brake fluid reservoir is filled to MAX line with fresh DOT 3 fluid
2. Clean any spilled brake fluid from painted surfaces immediately with water
3. Double-check all brake line fittings are torqued to specification
4. Verify proportioning valve mounting bolts are properly torqued
5. Remove all tools and materials from engine bay

Verification

• Start engine and pump brake pedal - pedal should be firm and not sink with constant pressure applied
• With engine running, verify brake booster function by noting the pedal should drop slightly when engine starts
• Recheck all connections at proportioning valve for any signs of leakage with engine running and brake pedal applied
• Test drive vehicle in a safe area at low speed (empty parking lot) - verify brakes apply smoothly and evenly without pulling to one side
• Perform several moderate stops from 25-30 mph to verify proper brake function and proportioning
• Check brake fluid level after test drive - should remain at MAX line with no drop
• Verify brake warning light on instrument cluster is not illuminated
• If any issues are detected (soft pedal, pulling, warning lights, leaks), DO NOT drive the vehicle - diagnose and correct before use

More procedures for this vehicle