Brake Booster Check Valve

Replace the brake booster check valve to ensure proper one-way vacuum flow and maintain power brake assist functionality.

Warnings

Tools required

Parts

• Brake booster check valve × 1 — Use OEM specification

Preparation

1. Park vehicle on level ground and engage parking brake
2. Turn engine off and remove keys from ignition
3. Allow engine to cool if recently operated
4. Open hood and secure with prop rod
5. Locate brake booster on firewall behind master cylinder (driver side)
6. Identify vacuum hose running from intake manifold to brake booster

Procedure

1. 1

   Locate the check valve
   The check valve is located in the vacuum hose between the engine vacuum source (intake manifold or carburetor base fitting) and the brake booster. Note: power brakes were an option (RPO J50) on the 1966 Corvette, so confirm this car is so equipped before proceeding. On the 1966 Corvette 327 V8, trace the vacuum hose from the booster inlet (front of booster canister) toward the intake manifold. The check valve is typically installed in the hose near the booster connection point, or directly into the booster grommet. Use your shop light to clearly identify the valve location.
2. 2

   Inspect the vacuum hose connection
   Examine how the check valve is installed. It may be pressed into a rubber grommet in the booster body, or installed inline within the vacuum hose itself. Note the orientation of the valve - the tapered end typically points toward the brake booster (away from manifold vacuum source). Take note of this orientation for proper reinstallation.
3. 3

   Remove vacuum hose from manifold side
   Disconnect the vacuum hose from the intake manifold fitting. Grasp the hose firmly near the connection point and twist while pulling to break the seal. If the hose is stubborn, carefully use a flathead screwdriver to gently pry between the hose and fitting. Avoid damaging the hose if it will be reused.
4. 4

   Remove check valve from booster
   If the check valve is pressed into the booster grommet, grasp the valve body and twist while pulling firmly to extract it from the rubber grommet. If installed inline in the hose, pull the hose off the valve barb on the booster side. You may need needle-nose pliers to grip the valve if access is tight. The valve should come free with moderate force.
5. 5

   Remove vacuum hose from old valve
   If the check valve was installed inline, remove the vacuum hose from both sides of the old valve. Twist and pull the hose to separate it from the valve barbs. Inspect the hose for cracks, hardening, or deterioration. Replace the hose if it shows any signs of damage.
6. 6

   Inspect booster grommet
   Examine the rubber grommet in the brake booster inlet. Check for cracks, tears, or hardening. The grommet should be pliable and intact. If damaged, the grommet should be replaced to prevent vacuum leaks. Clean any debris from the grommet bore.
7. 7

   Verify new check valve orientation
   Identify the directional markings on the new check valve. The valve allows vacuum flow in only one direction. The tapered or marked end must point toward the brake booster (away from the manifold). Most valves have an arrow or the word 'BOOSTER' indicating proper orientation. Hold the valve next to the installation location to confirm correct positioning.
8. 8

   Install new check valve into booster
   Push the new check valve firmly into the brake booster grommet with the correct orientation (tapered end toward booster). Apply steady pressure until the valve seats fully in the grommet. The valve should be firmly retained and not pull out easily. If installing inline in the hose instead, attach the check valve to the hose on the booster side first.
9. 9

   Connect vacuum hose to check valve
   Push the vacuum hose firmly onto the check valve barb. Ensure the hose is seated completely over the barb with no gaps. The connection should be tight and secure. If the hose is loose, consider replacing it or use a small hose clamp (not typically required on original equipment).
10. 10

    Reconnect hose to intake manifold
    Connect the other end of the vacuum hose to the intake manifold vacuum port. Push the hose firmly onto the fitting until it seats completely. Tug gently to verify a secure connection.
11. 11

    Test check valve operation
    With the engine off, attempt to blow through the vacuum hose from the booster side toward the manifold. Air should flow freely (valve open). Now attempt to blow in the opposite direction (manifold toward booster). You should feel significant resistance (valve closed). This confirms the check valve passes air out of the booster but blocks air returning into it. This confirms the check valve is functioning and installed in the correct direction.

Reassembly

1. No disassembly of other components was required for this procedure

Verification

• Start the engine and listen for any hissing sounds indicating vacuum leaks around the check valve connections
• With engine running, press the brake pedal. It should feel firm and require normal effort with power assist functioning
• Turn off the engine and wait 30 seconds. Press the brake pedal - you should get 2-3 power-assisted applications before the pedal becomes hard. This confirms the check valve is holding vacuum in the booster
• Perform a test drive in a safe area. Verify normal brake pedal feel and operation at various speeds
• If brake pedal is hard or requires excessive force, recheck check valve orientation and all vacuum connections for leaks

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