Vacuum Booster Diagnosis. Pontiac Sun Runner - 4WD (Canada) 1998

For 1990-2009 cars

### Booster System Check

1. Release the brake pedal.
2. Turn the ignition switch to the ON position.
3. Fully depress the brake pedal.
4. With the brake pedal pressed, turn the ignition switch to the LOCK position.
5. Inspect for a change in the pedal travel. If there is no change in the pedal travel, the booster is airtight.
6. If brake pedal travel exists after the engine is turned off, do the following:

• | Install an operable check valve and hose.

• | Repeat steps 1-4.

• | If there is no change in the pedal travel, replace the check valve and hose.

• | If brake pedal travel exists, replace the booster assembly.

7. Turn the ignition switch to the ON position and run engine for 15 seconds.
8. Turn the ignition switch to the LOCK position.
9. Pump the brake pedal until all of the reserve is exhausted from the booster.
10. Press the brake pedal with a force of 294 N (66 lbs).
11. With the brake pedal depressed, turn the ignition switch to the ON position.
12. Inspect the brake pedal movement:

• | If the brake pedal moves slightly to the floor, a reserve brake pedal distance is present. The booster is functioning normally.

• | If the brake pedal does not move slightly to the floor, do the following:

- | Install an operable check valve and hose.

- | Repeat steps 5-9. If the brake pedal moves slightly to the floor, replace the check valve and hose. If the brake pedal does not move slightly, replace the booster assembly.

13. Release the brake pedal.
14. Run engine for 15 seconds.
15. Without pressing the brake pedal, turn the ignition switch to the LOCK position.
16. Press the brake pedal several times slowly. Check for the following conditions:

• | If the brake pedal travel decreases with each brake pedal press, the booster is airtight and functioning normally.

• | If the brake press does not decrease in travel with each press, do the following:

- | Install an operable check valve and hose.

- | Repeat steps 10-13. If the brake pedal decreases with each brake pedal press, replace the check valve and hose. If the brake pedal press does not decrease in travel, replace the booster assembly.