42–10 Brake Pedal Linkage and
Mounting Plate
Inspection
Inspect the pedal, pedal linkage, and mounting plate
assembly for proper operation, to ensure that any
problems believed to be valve-related are not actu-
ally mechanism issues.
42–11 Air Brake Inspecting and
Leak Test
IMPORTANT: If any of the tests in the following
procedure fail, refer to
Group 42
of the
Business Class® M2 Workshop Manual
to test
individual air brake components and valves.
WARNING
Some steps in this operation require the parking
brakes to be released. Make sure the vehicle is on
a level surface and all tires are chocked. Failure to
do so could result in the vehicle rolling, causing
personal injury and/or vehicle damage.
1.
With the vehicle parked on a level surface, shut
down the engine, apply the parking brakes, and
chock all tires.
2.
Completely drain all air reservoirs.
3.
Install accurate test gauges in the primary and
secondary reservoirs.
4.
Start the engine and run it at a fast idle.
5.
Record reservoir pressures when the low-
pressure warning turns off.
6.
Record governor cut-out pressure and air dryer
purge pressure.
7.
Reduce service air pressure by applying and re-
leasing the service brakes several times, and
record governor cut-in pressure.
8.
Charge the air system to governor cut-out, shut
down the engine, and apply the parking brakes.
9.
Allow pressure to stabilize for one minute.
10. Observe the installed service reservoir gauges.
The pressure should not drop more than 10 psi
(69 kPa) within five minutes.
11. If necessary, start the engine and charge the air
system. Shut down the engine and release the
parking brakes.
12. Make and hold a full service brake application,
allowing the pressure to stabilize for one minute.
Observe the installed service reservoir gauges.
The pressure should not drop more than 15 psi
(103 kPa) in five minutes.
13. With the air system at full pressure and the en-
gine idling, perform the following:
•
On trucks, operate the parking brake con-
trol valve and note that the parking brakes
apply and release promptly as the control
valve knob is pulled out and pushed in on
the spring brake axles only.
•
On tractors, operate the trailer supply con-
trol valve knob. Note the air coming out of
the trailer control coupling. Operate the
park control knob and note that the parking
brakes apply and release promptly as the
knob is pulled out and pushed in. Block the
trailer supply coupling, and push the trailer
supply control valve and park control valve
knobs in. When the park control valve knob
is pulled out, the trailer supply knob should
also come out.
14. Build air system pressure to cut-out and shut
down the engine.
15. Completely drain the secondary (front axle) res-
ervoir. On vehicles equipped with a Dryer Reser-
voir Module (DRM) or AD-IS with the air dryer
attached to the reservoir, the primary (rear axle)
reservoir pressure should not drop below 65 psi
(448 kPa). On vehicles equipped with single
check valves, where the air dryer is not attached
to the reservoir, the primary reservoir should not
lose pressure.
16. Make a service brake application. The rear axle
brakes should apply and release and the brake
lights should illuminate.
On tractors, with the trailer supply knob pushed
in, the trailer control coupling should deliver air
during the brake application.
17. Push the trailer air supply valve knob in. With the
secondary reservoir still completely drained,
slowly drain the primary reservoir and record the
Brakes
42
Business Class M2 Maintenance Manual, November 2015
42/10
Property of American Airlines
