PART 7: STARTING & OPERATING THE VEHICLE
PB1319 (CAT. NO. 5296 ) —80— 22-01691 (R02/02)
Overheated Brakes
Under normal braking conditions, the energy generated will bring the
internal brake drum temperature to about 500° F (260° C). This is
well within the safe zone: The maximum safe temperature of linings
for drum type brakes is usually about 800° F (427° C).
But if service brakes are used improperly or for prolonged periods,
internal brake drum temperatures may commonly exceed 800° F
(427° C). Such brake overheating may be detected by a burning
smell or smoke coming from a drum. If this occurs, you should imme-
diately stop and check for cracked brake drums or lining fires. If nei-
ther exists, get back behind the wheel and resume a slow speed as
soon as possible to cool the brakes.
Parking Brakes and Their Use
The yellow diamond-shaped knob on your instrument panel controls
your parking brakes. These are spring brakes that you activate by
releasing air pressure from their chambers. When they are not in
use, air pressure compresses the springs and releases the brakes.
But putting the valve in the Park position exhausts air from the cham-
bers and allows the springs to extend and apply the brakes. Also, if
your system air drops below the safe operating level, the spring
brakes will apply automatically, bringing your vehicle to a stop.
Red / Yellow Controls
WARNING! On trailers built before March 1975 you may
not have parking brakes if the trailer reservoir pressure
leaks down. If you depend on them to hold your vehicle,
they could release & cause a serious accident. These
older trailers have emergency brakes not designed for
parking. They will apply only if there is enough trailer
reservoir pressure. Don’t use your trailer emergency
brakes for parking. Apply your tractor parking valve too.
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