Brake Booster Check Valve

This procedure replaces the brake booster check valve, which prevents vacuum loss in the brake booster system and ensures proper power brake assist function.

Warnings

Tools required

Parts

• Brake booster check valve with grommet × 1 — Use OEM Kia specification

Preparation

1. Ensure engine is off and has cooled completely
2. Open the hood and secure it in the upright position
3. Locate the brake booster on the driver's side firewall behind the master cylinder
4. Identify the vacuum hose connecting from the intake manifold to the brake booster - the check valve is installed in this connection point at the brake booster
5. Clean the area around the check valve and vacuum hose connection to prevent debris from entering the system

Procedure

1. 1

   Release vacuum hose clamp
   Locate the vacuum hose clamp securing the hose to the brake booster check valve. Squeeze or loosen the clamp (depending on type) and slide it back along the vacuum hose away from the brake booster to provide clearance for hose removal.
2. 2

   Remove vacuum hose from check valve
   Firmly grasp the vacuum hose near the connection point and pull it straight off the check valve with a twisting motion. If the hose is difficult to remove, gently work a flathead screwdriver between the hose and check valve fitting to break the seal. Inspect the hose end for cracks or damage and replace if necessary.
   ⚠Do not pull on the hose itself away from the connection point, as this can tear or damage the vacuum hose. Always pull from the base near the fitting.
3. 3

   Extract check valve from brake booster
   The check valve is press-fitted into a rubber grommet in the brake booster housing. Grasp the check valve body firmly with pliers and pull straight out with steady force. The valve and grommet may come out together or separately. If the grommet remains in the booster, use a flathead screwdriver or pick to carefully pry it out without damaging the booster housing bore.
   ⚠Do not twist or bend the check valve excessively during removal, as this may damage the brake booster housing bore or leave debris behind.
4. 4

   Inspect brake booster bore
   Use a flashlight to inspect the check valve bore in the brake booster. Look for cracks, damage, or debris. Clean the bore with a shop towel if necessary. Verify that no pieces of the old grommet remain stuck in the bore. The bore surface should be clean and smooth for proper seal of the new grommet.
5. 5

   Verify new check valve operation and orientation
   Before installation, test the new check valve by blowing through it in both directions. Air should flow freely from the engine side (towards booster) but should be blocked or restricted when blowing from the booster side (towards engine). This one-way function is critical. Identify the correct orientation - the arrow on the valve body (if present) should point toward the brake booster, or the tapered end typically inserts into the booster.
   ⚠️Installing the check valve backwards will cause complete loss of brake power assist and can result in brake system failure. Verify proper orientation before installation.
6. 6

   Install new grommet if separate
   If the new check valve kit includes a separate rubber grommet, install the grommet into the brake booster bore first. Push it in firmly by hand until it seats completely flush with the booster housing. The grommet should fit snugly without gaps around the bore perimeter.
7. 7

   Install check valve into brake booster
   Align the check valve with the grommet or booster bore, ensuring correct orientation (arrow or tapered end toward booster). Push the valve straight into the grommet with firm hand pressure until it seats completely. You should feel or hear a positive click or pop when the valve is fully seated. The valve should not pull out easily when tugged gently.
   ⚠Do not use excessive force or tools to install the check valve, as this may damage the grommet or valve. Firm hand pressure should be sufficient.
8. 8

   Reconnect vacuum hose
   Push the vacuum hose onto the check valve fitting with a firm twisting motion until it is fully seated against the base of the fitting. Ensure the hose is pushed on as far as it will go. Slide the hose clamp back into position over the connection point and secure it tightly.

Reassembly

1. Verify the vacuum hose clamp is properly positioned and secured
2. Double-check that the vacuum hose has no kinks or sharp bends that could restrict airflow
3. Ensure all connections are tight and no tools or parts have been left in the engine bay

Verification

• Start the engine and listen for any hissing sounds near the brake booster area, which would indicate a vacuum leak at the check valve or hose connection
• With the engine running, press the brake pedal several times - it should feel firm but require moderate effort with power assist active. A hard pedal indicates check valve failure or improper installation
• Turn off the engine and wait 30 seconds, then press the brake pedal - you should get 2-3 power-assisted pedal applications before the pedal becomes hard. This confirms the check valve is holding vacuum properly
• If the brake pedal is excessively hard or no power assist is present, stop immediately and verify check valve orientation and proper seating. Do not drive the vehicle until proper brake assist is confirmed
• Test drive in a safe area at low speed to confirm normal brake operation before returning to regular use

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