CHASSIS INFORMATION — 10
216
2008 IMPERIAL
Applied Pressure Loss Test:
This test will verify the rate of maximum
acceptable air system pressure loss with only
the service brakes applied. Do not use other
pneumatically operated devices during this test.
This test requires a
fl
at, level surface as the
park brake will be released with the engine off.
Chock wheels to prevent vehicle movement.
1. Start engine.
2. Run engine until a chuff (air release) is
heard from the air dryer.
3. Shut engine off.
4. Release the park brake.
5. Apply and hold service brake pedal.
Note system pressure after air system pressure
stabilizes. Air system pressure must not lose
more than 3 psi per minute.
Low Air Warning Test:
This test will verify low air warning buzzer/
lamp activation. A Low Air warning buzzer or
lamp will sound/illuminate should air system
pressure fall to 60 or 65 psi.
1. Start engine.
2. Run engine until low air warning
indicators are inactive.
3. Shut engine off then turn key to
ignition on.
4. Fan (apply/release in quick succession)
service brake pedal.
Low air warning indicator will sound no lower
than 60 psi.
Park Brake Apply Test:
The park brake will automatically apply if low
air warning indicator(s) are ignored and system
pressure falls well below safe operating levels.
A
fl
at, level surface is required as the park brake
will be released with the engine off. Chock
wheels to prevent vehicle movement.
1. Start engine.
2. Run engine until low air warning
indicators are inactive.
3. Shut engine off.
4. Release park brake.
5. Fan (apply/release in quick succession)
service brake pedal.
The park brake will automatically apply
between 20 to 40 psi.
Park Brake Hold Test:
This test will verify engagement of the park
brake. A
fl
at, level surface is required. While the
test is performed with the park brake applied,
use precautions in case of vehicle movement.
This test only veri
fi
es the park brake is engaged.
It is not intended to verify the maximum amount
of braking force created by the park brake.
1. Start engine.
2. Place transmission into gear. Do not
release park brake.
3. Apply light throttle, not to exceed 1,000
RPM.
Test con
fi
rms that the park brake is engaged
and holding.
Air Governor Cut-in Test:
The air governor controls action of the air
system pump. This will con
fi
rm the air governor
cut-in pressure setting.
1. Start engine.
2. Run engine until a chuff (air release) is
heard from the air dryer.
3. Fan (apply/release in quick succession)
service brake pedal until system
pressure is between 110 and 115 psi.
Air governor cut-in pressure is approximately
115 psi.
Brake Grab Test:
A brake grab test will verify brake friction
torque between the front wheels. The test
requires a rapid and full pressure application of
service brake pedal. Use proper precautions to
prevent movement of cargo or other unsecured
items. This is a single vehicle test. Select the
most deserted, level road surface as possible
(i.e. a large, empty parking lot). Road crown
may affect test results, depending on severity of
crown.
1. Start engine.
2. Run engine until a chuff (air release) is
heard from the air dryer.
3. Release park brake.
4. Accelerate to approximately 5 mph.
5. Rapidly and
fi
rmly apply service
brake pedal to bring vehicle to an
abrupt stop.
The steering wheel will not pull to the
left or right if front wheel braking torque is
symmetrical.
