TM-5-3805-254-14-P-2
TRUCK, DUMP, 20 TON, 6X4, ON-OFF HIGHWAY 71,000 GVW, IHC MODEL F-5070 (CCE)
TECHNICAL MANUAL; OPERATOR’S, ORGANIZATIONAL, DIRECT SUPPORT, GENERAL SUPPORT AND DEPT MAINTENANCE MANUAL (INCLUDING REPAIR PARTS INFORMATION AND SUPPLEMENTAL MAINTENANCE INSTRUCTIONS)
JUNE 1980
TM-5-3805-254-14-P-2 - Page 145 of 894
BRAKES-AIR
TRUCK SERVICE MANUAL
SERVICE CHECKS
1
.
With air brake system charged, test with soap
suds for leakage past the key.
Also check for
leakage through the body by coating the outside
of the drain cock with soap suds.
Leakage in
excess of a 3" soap bubble in 3 seconds is not
permissible.
2
.
Leakage is caused by dirty or scored key or
body.
Leakage due to dirt is corrected by
cleaning parts and applying a thin coating of Item
1 in LUBRICANT SPECIFICATIONS on the key.
Leakage due to a scored key or body cannot be
repaired and the drain cock must be replaced.
SAFETY VALVE
DESCRIPTION
The purpose of the safety valve is to protect the air
brake system against excessive air pressure.
Should the
air pressure in the air brake system rise above the
setting of the safety valve at 150 pounds, the valve
opens and permits pressure above 150 pounds to be
exhausted.
It is located on the supply reservoir.
The safety valve is a piston type valve (Fig.
2).
The piston is equipped with an O ring type seal which
seats in the body of the valve.
Fig.
2
Sectional View of Piston Type Safety Valve
MAINTENANCE
Once each year or every 100,000 miles the safety
valve should be removed and thoroughly cleaned.
SERVICE CHECKS
Operating Test
The safety valve may be tested to be sure it is
operative by pulling the exposed end of the piston. This
removes the spring load from the piston and permits the
valve
to
exhaust.
Leakage Test
Leakage at the piston in the body should not
exceed a 3" soap bubble in 3 seconds.
If air leakage is
excessive the valve must be replaced since it is only
serviced as a complete component.
The safety valve should be set to "blow off" at
approximately 150 pounds.
The pressure setting may be
adjusted by turning the adjusting nut clockwise to raise
the pressure setting and turning the adjusting nut
counterclockwise to lower the pressure setting.
Since the safety valve must be removed to perform any
adjustments, it is suggested that the valve be replaced
when any defect is detected.
CAUTION: When replacing the safety valve be sure to
drain all air from the supply reservoir. Draining the
primary and secondary reservoirs are not required since
they are protected by check valves.
AIR PRESSURE GAUGE
DESCRIPTION
The purpose of the air pressure gauge is to
register the amount of reservoir air pressure in the air
system.
While air pressure gauges of this type are
commercially accurate, they must never be confused
with or substituted for test air gauges, which are intended
primarily for accurately checking air pressure in the air
brake system.
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