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Home >> Hummer >> 2003 >> H2 >> Repair and Diagnosis >> External Pages >> Different car >> Section 184 (Disc Brakes) >> System Tests >> Brake System Vacuum Source Test
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Brake System Vacuum Source Test

WARNING: This page is about a different car, the 2003 Oldsmobile Aurora. However, it is still accessible from the selected car via links, so may be relevant.
  1. Disconnect the engine vacuum hose from the power brake booster check valve.
  2. Install a vacuum gage 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 specified 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 tight connection to the engine, collapse, deformation or contamination, cracks, cuts and dry-rot.
  8. If any of these conditions were found with the engine vacuum hose, replace the hose, then repeat steps  2 - 4 .
  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 power brake booster check valve from the booster.
  11. Install the check valve to the engine vacuum hose.
  12. Install the vacuum gage 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 specified normal engine vacuum range. Specification 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  11 - 15 .
  18. Inspect the brake booster check valve grommet for a firm connection to the power brake booster, deformation or contamination, cracks, cuts and dry-rot.
  19. If any of these conditions were found with the check valve grommet, replace the grommet.
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