TRUCK SERVICE MANUAL
RESERVOIR DRAIN COCK SAFETY VALVE
PRESSURE GAUGE - LOW PRESSURE INDICATOR - STOP LIGHT SWITCH
3. Moisture taken in with the air through the
and necessitates draining the reservoirs daily in
The air reservoir (air tank) function is to provide a
cold weather and every week in warm weather
volume of compressed air used in braking the vehicle.
by opening the drain cock located on the bottom.
Be sure to close the drain cocks after all
moisture has been removed.
Drain air reservoirs regularly as required.
Local conditions govern frequency. In dry climates, for
example, once a month may be sufficient, while in humid
Another function of a reservoir is to provide a place
areas it may be necessary to drain reservoirs daily.
where the air, heated during compression, may cool and
cause the oil and water vapors to condense.
When draining the air reservoirs, open the drain
cock and let the air bleed off. Be sure to leave the cock
The combined volume of all service reservoirs and
supply reservoirs are 12 times the combined volume of
all service brake chambers at maximum travel of the
pistons or diaphragms. The size of air tanks should
never be altered without IH Engineering approval.
Drain cocks have a brass body fitted with a tapered
The reservoirs should be completely drained daily.
brass key. The drain cock is open when the handle is
If an automatic drain device is used, the automatic drain
parallel to the body and closed when the handle is at
should be checked periodically to determine if it is
right angles to the body.
functioning properly. When manually draining tanks,
satisfactory draining is only accomplished by leaving the
Drain cocks are installed in the bottom of each reservoir
drain cocks open after all air has escaped and all
(Fig. 1) in the air brake system to provide a convenient
collects in the reservoirs.
Reservoirs are tested against a 300 pound
pressure and treated on the inside with a rust preventive.
Always open a drain cock by hand. Never strike the
handle with a hammer or any other instrument, as the
cock will be damaged and leakage will develop.
1. Leakage Tests. With the air brake system
charged, use Leak Detector Tester (SE2326) to
check for leakage on outside surfaces of
reservoirs. If any leakage is found, replace the
2. Inspection. Inspect inside and outside surfaces
for damage or corrosion. A small flashlight is
helpful when inspecting the interior. If damage
or corrosion is found that would weaken the
reservoir, replace the reservoir.
Fig. 1 Reservoir, Safety Valve and Drain Cock