Brake System Vacuum Source Test

2004 Oldsmobile Bravada AWDSECTION Brake System Vacuum Source Test
WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2002 GMC Yukon XL, 2002 GMC Yukon, 2002 Chevrolet Tahoe, 2002 Chevrolet Suburban, and 2002 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
  1. Disconnect the engine vacuum hose from the vacuum brake booster check valve.
  2. Install a vacuum gauge to the engine vacuum hose.
  3. Start the engine and allow the engine to idle until normal operating temperatures are reached.
  4. Check to see if the engine vacuum reading is within the normal engine vacuum range of 14-20 in. Hg (47-68 kPa).
  5. Turn the ignition OFF.
  6. If the engine vacuum reading is within the specified normal range, proceed to step  10.
  7. If the engine vacuum reading is NOT within the specified normal range, inspect the engine vacuum hose for a tight connection to the engine, collapse, deformation or contamination, cracks, cuts or dry-rot.
  8. If any of these conditions were found with the engine vacuum hose, replace the hose, then repeat steps  24 .
  9. If none of these conditions were found with the engine vacuum hose, then there is an engine vacuum source problem, check the engine vacuum system.
  10. Remove the vacuum brake booster check valve from the booster.
  11. Install the check valve to the engine vacuum hose.
  12. Install the vacuum gauge to the check valve.
  13. Start the engine and allow the engine to idle until normal operating temperatures are reached.
  14. Turn the ignition OFF.
  15. Check to see if the engine vacuum reading is maintained within the normal engine vacuum range of 14-20 in. Hg (47-68 kPa).
  16. If the engine vacuum reading is maintained within the specified normal range, proceed to step  18.
  17. If the engine vacuum reading is NOT maintained within the specified normal range, replace the brake booster check valve, then repeat steps  1115 .
  18. Inspect the brake booster check valve grommet for a firm connection to the vacuum brake booster, deformation or contamination, cracks, cuts or dry-rot.
  19. If any of these conditions were found with the check valve grommet, replace the grommet.
RENDER: 1.0x

NO RELATED

Recommended Tools & Savings

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Affiliate disclosure: We may earn a commission at no extra cost to you.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • You smell fuel, burning insulation, or see smoke.
  • Brakes feel soft, pull hard to one side, or make grinding noises.
  • The engine overheats, stalls repeatedly, or misfires under load.
  • You are missing required tools, torque specs, or safe lifting equipment.
  • You are not confident in the next step or safety outcome.