Brake System Vacuum Source Test
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Brake System Vacuum Source Test
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1.
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Note
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Engine temperature, accessory load, and elevation level will affect engine vacuum.
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Vacuum readings will decrease by approximately 2.7 kPa (0.8 in Hg) for every 305 m (1000 ft) of elevation above sea level.
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Disconnect the engine vacuum hose from the vacuum brake booster check valve.
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2.
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Install a vacuum gauge to the engine vacuum hose.
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3.
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Start the engine and allow the engine to idle until normal operating temperatures are reached.
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4.
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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.
Specification
47-68 kPa (14-20 in Hg)
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5.
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Turn the ignition OFF.
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6.
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If the engine vacuum reading was within the specified normal range, proceed to step 10.
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7.
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If the engine vacuum reading was NOT within the specified normal range, inspect the engine vacuum hose for the following conditions:
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Loose connection to the engine
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Collapse, deformation or contamination
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8.
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If any of these conditions were found with the engine vacuum hose, replace the hose, then repeat steps 2-4.
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9.
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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.
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10.
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Remove the vacuum brake booster check valve from the booster.
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11.
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Install the check valve to the engine vacuum hose.
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12.
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Install the vacuum gauge to the check valve.
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13.
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Start the engine and allow the engine to idle in PARK with the A/C system OFF, until normal operating temperatures are reached.
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14.
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Turn the ignition OFF.
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15.
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Check to see if the engine vacuum reading is maintained within the specified normal engine vacuum range.
Specification
47-68 kPa (14-20 in Hg)
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16.
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If the engine vacuum reading is maintained within the specified normal range, proceed to step 18.
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17.
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If the engine vacuum reading is NOT maintained within the specified normal range, replace the brake booster check valve, then repeat steps 11-15.
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18.
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Inspect the brake booster check valve grommet for the following conditions:
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Loose connection to the vacuum brake booster
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Deformation or contamination
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19.
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If any of these conditions were found with the check valve grommet, replace the grommet.
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