This procedure covers inspection and replacement of the brake booster check valve, which maintains vacuum in the brake booster and prevents loss of power assist.

Warnings

Tools required

Parts

• Brake booster check valve × 1 — Use OEM Toyota part number
• Vacuum hose grommet (if damaged) × 1 — Use OEM specification

Preparation

1. Park vehicle on level ground and apply parking brake
2. Turn ignition OFF and remove key
3. Allow engine to cool for at least 30 minutes if recently operated
4. Open hood and secure with prop rod
5. Locate brake booster on driver's side firewall - it is a large black canister behind the brake master cylinder
6. Identify the vacuum hose connection on the front of the brake booster (connects to intake manifold)

Procedure

1. 1

   Access and inspect check valve location
   Locate the brake booster check valve where the vacuum hose connects to the brake booster body. The check valve is typically inserted into a rubber grommet in the booster's vacuum port. On 2019-2024 RAV4 2.5L models, this is accessed from the driver's side of the engine bay. Use a shop light to clearly see the connection point and inspect for obvious damage, cracks, or deterioration of the vacuum hose and grommet.
2. 2

   Remove vacuum hose from check valve
   Grasp the vacuum hose firmly near the check valve connection. Gently twist and pull the hose straight off the check valve. The hose should release with moderate force. If the hose is stuck due to age, carefully work it back and forth while pulling. Avoid using excessive force that could break the check valve inside the booster. Inspect the inside of the hose end for cracks, deterioration, or contamination.
   ⚠Do not use sharp tools to pry the hose off, as this can damage the check valve or grommet. If hose is severely stuck, carefully cut it away from the valve and replace the hose.
3. 3

   Remove check valve from brake booster
   Grasp the check valve body with needle-nose pliers or by hand. Pull straight out from the booster with steady, firm pressure. The valve is retained only by the rubber grommet and should pull free. If difficult to remove, gently twist while pulling. Once removed, inspect the rubber grommet remaining in the booster for cracks, hardening, or damage. The grommet should be pliable and intact.
4. 4

   Test old check valve function
   Blow air through the check valve in both directions to verify failure mode. Air should flow freely when blown from the booster side (smaller end) toward the hose side, but should be blocked or significantly restricted when blown from the hose side toward the booster. If air flows freely in both directions, the valve has failed and must be replaced. Also inspect the valve body for cracks or damage.
5. 5

   Inspect and clean grommet seat
   If the rubber grommet remained in the booster, remove it using needle-nose pliers or a pick tool. Pull straight out carefully to avoid tearing. Inspect the grommet for age hardening, cracks, or deformation. Clean the valve seat in the booster using brake cleaner and a shop towel to remove any debris or contamination. The seat must be clean and dry for proper seal.
   ⚠Be careful not to allow debris or brake cleaner to enter the booster vacuum chamber. Keep the opening pointed downward during cleaning and use minimal cleaner.
6. 6

   Install new grommet if needed
   If the original grommet shows any signs of damage, deterioration, or hardening, install a new grommet. Press the new grommet into the booster vacuum port by hand, ensuring it seats fully and evenly in the bore. The grommet should sit flush with the booster body surface. A small amount of clean brake fluid on the grommet outer surface can ease installation.
7. 7

   Test new check valve
   Before installation, verify the new check valve operates correctly. Blow air through the valve in both directions. Air should flow freely from the booster side (smaller end) to the hose side, but should be blocked when reversed. This confirms proper one-way valve operation. Inspect the valve for any shipping damage or defects.
8. 8

   Install new check valve
   Insert the new check valve into the grommet in the brake booster, paying careful attention to orientation. The tapered or smaller end of the valve typically faces INTO the booster, while the larger end faces out toward the vacuum hose. Verify correct orientation with the old valve or service documentation. Push the valve firmly into the grommet until it seats completely and cannot be pushed further. The valve should be secure and not pull out easily.
   ⚠️CRITICAL: Check valve MUST be installed in correct orientation. Reversed installation will prevent brake booster function, resulting in loss of power assist and very hard brake pedal. Verify orientation before proceeding.
9. 9

   Reconnect vacuum hose
   Push the vacuum hose firmly onto the check valve until it is fully seated. The hose should push on approximately 20-25mm (0.75-1 inch) onto the valve barb. Tug on the hose to verify it is securely connected and will not pull off. Inspect the entire vacuum hose run from the booster to the intake manifold for cracks, splits, or other damage that could cause vacuum leaks.
10. 10

    Perform initial brake booster function test
    With engine OFF, press the brake pedal several times (5-6 pumps) to deplete any residual vacuum in the booster. The pedal should become progressively harder with each pump. Then start the engine while maintaining light foot pressure on the brake pedal. The pedal should sink slightly (typically 5-10mm) when the engine starts and vacuum builds, indicating the check valve and booster are functioning correctly.
    ⚠️If pedal does NOT sink when engine starts, STOP and recheck check valve installation and orientation. Do not drive vehicle until proper booster function is confirmed.

Reassembly

1. Ensure vacuum hose is properly routed without kinks or sharp bends
2. Verify all connections are secure and no vacuum leaks are present
3. Close hood and remove prop rod

Verification

• With engine OFF, pump brake pedal 5-6 times to deplete vacuum. Pedal should become hard
• Start engine while applying light pressure to brake pedal. Pedal should sink slightly when engine starts
• With engine running, hold firm pressure on brake pedal for 30 seconds. Pedal should not sink further (no booster leakage)
• Turn engine OFF. Wait 1 minute, then press brake pedal. First pedal stroke should be power-assisted (softer than subsequent strokes), confirming check valve is holding vacuum
• Perform test drive in safe area at low speed to confirm normal brake pedal feel and power assist before returning to normal operation
• Listen for any hissing sounds near brake booster while engine is running, which would indicate vacuum leak

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