Brake System Vacuum Source Test

Brake System Vacuum Source Test

Important:
* Engine temperature, accessory load, and elevation level will affect engine vacuum.

* Vacuum readings will decrease by approximately 2.7 kPA (0.8 in HG) for every 305 m (1000 ft) of elevation above sea level.

Disconnect the engine vacuum hose from the vacuum brake booster check valve.
* Install a vacuum gage to the engine vacuum hose.
* Start the engine and allow the engine to idle until normal operating temperatures are reached.
* With the vehicle in PARK, the engine idling, and the air conditioning (A/C) system OFF, check to see if the engine vacuum reading is within the specified normal engine vacuum range.

47-68 kPa (14-20 in Hg)

* Turn the ignition OFF.
* If the engine vacuum reading is within the specified normal range, proceed to step 10.
* If the engine vacuum reading is NOT within the specified normal range, inspect the engine vacuum hose for the following conditions.

* Loose connection to the engine
* Collapse, deformation or contamination
* Cracks, cuts, dry-rot

* If any of these conditions were found with the engine vacuum hose, replace the hose, then repeat steps 2-4.
* 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.
* Remove the vacuum brake booster check valve from the booster.
* Install the check valve to the engine vacuum hose.
* Install the vacuum gage to the check valve.
* Start the engine and allow the engine to idle in PARK with the A/C system OFF, until normal operating temperatures are reached.
* Turn the ignition OFF.
* Check to see if the engine vacuum reading is maintained within the specified normal engine vacuum range.

47-68 kPa (14-20 in Hg)

* If the engine vacuum reading is maintained within the specified normal range, proceed to step 18.
* If the engine vacuum reading is NOT maintained within the specified normal range, replace the brake booster check valve, then repeat steps 11-15.
* Inspect the brake booster check valve grommet for the following conditions:

* Loose connection to the vacuum brake booster
* Deformation or contamination
* Cracks, cuts, dry-rot

* If any of these conditions were found with the check valve grommet, replace the grommet.