Brake Booster Check Valve

Inspection and replacement of the brake booster check valve on the Rivian EDV 500's electric brake boost system to ensure proper vacuum assist and brake performance.

Warnings

Tools required

Parts

• Brake booster check valve × 1 — Use OEM specification
• Vacuum hose grommet × 1 — Use OEM specification
• Vacuum line clamps × 2 — Spring type or worm gear

Fluids

• DOT 4 Brake Fluid — 0.5 qt

Preparation

1. Park vehicle on level surface and engage parking brake firmly
2. Turn off vehicle and remove key fob from cabin to prevent accidental startup
3. Open hood and disconnect 12V battery negative terminal, wait 5 minutes for system capacitors to discharge
4. Verify high-voltage system is de-energized using digital multimeter if equipped - check for 0V at service disconnect
5. Place fender covers to protect paint from brake fluid damage
6. Locate brake booster assembly on driver side firewall behind master cylinder
7. Identify electric vacuum pump mounted to brake booster (black cylindrical unit with electrical connector)
8. Take photos of vacuum hose routing and check valve orientation for reference during reassembly
9. Ensure adequate lighting of work area

Procedure

1. 1

   Access brake booster check valve
   Remove any engine covers or cowl panels obstructing access to the brake booster area. On the EDV 500, you may need to remove the upper cabin air intake duct. Remove fasteners with 10mm socket and carefully pull panels away. The check valve is located on the vacuum hose between the electric vacuum pump and the brake booster chamber.
2. 2

   Disconnect electric vacuum pump connector
   Locate the electrical connector on the electric vacuum pump. Press the locking tab and carefully pull the connector straight off the pump. This prevents the pump from activating during service. Inspect connector terminals for corrosion or damage.
3. 3

   Test existing check valve function
   Before removal, test the current check valve. Disconnect the vacuum hose from the pump side of the check valve. Connect vacuum pump with gauge to this port. Apply 20 inches Hg vacuum and observe gauge for 60 seconds. A properly functioning check valve should hold vacuum with less than 2 inches Hg loss per minute. Note results for comparison. Also verify the valve allows airflow in only one direction by attempting to blow through it both ways.
4. 4

   Release brake system vacuum reserve
   With the pump disconnected, pump the brake pedal approximately 20-30 times to exhaust vacuum reserve from the brake booster. You will feel the pedal become progressively firmer as vacuum is depleted. This equalizes pressure before removing the check valve.
   ⚠Do not start vehicle or reconnect vacuum pump during this step. The pedal will feel very hard when vacuum is fully depleted - this is normal.
5. 5

   Remove vacuum hose clamps
   Using needle nose pliers or flathead screwdriver (depending on clamp type), carefully remove or loosen the hose clamps on both sides of the check valve. Spring-type clamps can be compressed and slid down the hose. Worm-gear clamps should be loosened but not fully removed. Note the orientation of the check valve arrow - it should point toward the brake booster (away from pump).
6. 6

   Remove check valve from vacuum hoses
   Gently twist and pull the check valve from both vacuum hoses. The valve may be firmly seated in rubber grommets. If stuck, use a slight twisting motion while pulling straight out. Avoid damaging the vacuum hoses. Inspect both hose ends for cracks, deterioration, or collapsed sections. Replace hoses if any damage is found.
7. 7

   Inspect vacuum hose grommets and ports
   Examine the rubber grommets in both vacuum hose ends where the check valve was seated. Look for tears, hardening, or deformation. Check the brake booster vacuum port and pump discharge port for debris, corrosion, or damage. Clean ports with a lint-free cloth if needed. Replace grommets if they show signs of wear.
8. 8

   Install new check valve
   Verify the new check valve has the directional arrow clearly visible. Apply a small amount of clean brake fluid or silicone lubricant to the check valve nipples. Insert the valve into the vacuum hoses with the arrow pointing toward the brake booster (away from pump). Push firmly until the valve seats fully into both grommets. The valve should be secure with no gaps visible at the connections.
9. 9

   Reinstall vacuum hose clamps
   Position new or existing hose clamps over the hose-to-check-valve connections. Ensure clamps are positioned 1/4 to 1/2 inch from the hose ends, securing the hose firmly to the check valve barbs. Tighten worm-gear clamps snugly but do not overtighten (approximately 15-20 inch-lbs) to avoid damaging the hoses. For spring clamps, ensure they are fully seated in the groove.
10. 10

    Test new check valve function
    Before reconnecting the pump, repeat the vacuum test performed in Step 3. Disconnect the hose from pump side, apply 20 inches Hg vacuum, and verify the valve holds vacuum with minimal loss. Test directional flow by attempting to blow through the valve - air should only pass from pump side toward booster side, not in reverse. If valve fails either test, it is defective and must be replaced.
11. 11

    Reconnect electric vacuum pump
    Reconnect the electrical connector to the electric vacuum pump. Ensure the connector locks fully with an audible click. Verify the connector is seated completely with no gaps.
12. 12

    Reconnect 12V battery and initialize system
    Reconnect the 12V battery negative terminal. Turn the vehicle to ON position without starting (if applicable to operating mode). The electric vacuum pump should activate automatically to rebuild booster vacuum. You should hear the pump running for 30-90 seconds. Monitor for any unusual noises or vacuum leaks (hissing sounds).
13. 13

    Check brake fluid level
    Open the brake fluid reservoir cap and verify the fluid level is between MIN and MAX marks. The level should not have changed during this procedure, but verify to ensure system integrity. Top off with fresh DOT 4 brake fluid only if needed. Do not overfill.
14. 14

    Test brake pedal feel and function
    With vehicle still stationary, pump the brake pedal several times. The pedal should feel firm with normal assist after 2-3 pumps once vacuum is built up. Listen for the vacuum pump to cycle on if vacuum drops. The pedal should not feel excessively hard or spongy. Compare pedal feel to normal operation before repair.

Reassembly

1. Reinstall any engine covers, cowl panels, or air intake ducts removed during access
2. Ensure all fasteners are properly tightened and panels are securely seated
3. Remove fender covers and clean any brake fluid spills from painted surfaces immediately
4. Verify all tools and parts have been removed from engine compartment
5. Double-check that vacuum pump electrical connector is fully engaged

Verification

• Start vehicle or activate drive mode and verify no warning lights appear on instrument cluster related to brake system
• Listen for proper electric vacuum pump operation - should run briefly at startup then shut off when vacuum reserve is achieved
• With vehicle running, pump brake pedal 5-6 times and hold pressure on pedal - the vacuum pump should activate to restore vacuum
• Perform stationary brake pedal test: press pedal firmly with normal force and verify it provides consistent resistance with power assist - pedal should not sink or feel hard
• Inspect all vacuum connections for leaks while pump is running - listen for hissing and look for any disconnected hoses
• Test drive vehicle in safe area at low speed (under 15 mph) and verify normal brake function with proper pedal feel and stopping power
• After test drive, recheck vacuum hose connections and check valve area for any signs of leakage or loose components
• Perform final brake pedal check after vehicle has sat for several hours - pedal should still have assist for first application, indicating check valve is holding vacuum reserve properly
• If any abnormalities are detected in brake feel, stopping power, or warning lights, do NOT drive vehicle - seek immediate professional service

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