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Reservoir
Brake Valve
Trailer Hand
Control Valve
3. Apply and hold a full foot brake valve application.
Check exhaust port of Trailer Control Valve for leakage
with soap solution. Permissible leakage is a one inch
bubble in five seconds (100 sccm). (Note: On some
vehicles, an exhaust line is connected to the exhaust
port and piped outside the cab in which case it may
be necessary to disconnect this line to make leakage
check.)
B. If Double Check Valve is to be bench tested or tested on
the vehicle, two separately controlled air supplies must
be connected to the inlet ports.
1. Install an accurate test gauge in the outlet port or in
a line from outlet port.
2. Apply and release air to one inlet port and note that
gauge registers application and release.
3. Repeat by applying and releasing air to other inlet
port.
4. Leakage check should be performed at inlet ports of
valve in the following manner:
a. Disconnect line from one inlet port.
b. Apply air to other inlet port and coat opposite
inlet port with soap solution. Permissible leakage is
a one inch bubble in five seconds (100 sccm).
c. Repeat Step ībī applying air to other inlet port
while checking opposite inlet port for leakage.
If the Double Check Valve does not function as described or
if leakage is excessive, it is recommended that the valve be
repaired or replaced with genuine Bendix parts. The follow-
ing instructions should prove helpful:
DISASSEMBLY
1. Remove end cap(s) from valve.
2. Remove grommets (if applicable).
3. Remove shuttle and/or shuttle guide, disc and/or disc
guide (depending upon type of valve).
CLEANING AND INSPECTION
1. Clean all metal parts in a cleaning solvent.
2. Inspect all metal parts for signs of cracks, wear or dete-
rioration. Replace all parts not considered serviceable.
3. Replace all rubber parts.
ASSEMBLY
1. Install disc guide, disc and/or shuttle and shuttle guide.
2. Coat all static seals such as o-rings, grommets, etc.
with BW 650M Silicone lubricant (BW 291126). It is not
necessary to lubricate shuttles or discs.
3. Install grommets.
4. Install end cap(s).
TESTING OF REBUILT DOUBLE CHECK VALVE
SERVICE CHECKS
OPERATING AND LEAKAGE TEST
A. When the Double Check Valve is used in conjunction
with a Trailer Control Valve, the following operating and
leakage test can be made:
1. Apply and release foot brake valve and note that the
brakes apply and release on both tractor and trailer.
2. Apply and release the Trailer Control Valve and note
that only the trailer brakes apply and release. With
trailer control valve applied check exhaust port of
foot brake valve for leakage with soap solution.
Permissible leakage is a one inch bubble in five
seconds (100 sccm).
Reservoir
Reservoir
Trailer Supply
Spring Brake Control
Double Check
Valve
FIGURE 4 - DOUBLE CHECK VALVE: SYSTEM WITH TWO
SUPPLY SOURCES
PP-7
PP-1
FIGURE 3 - DOUBLE CHECK VALVE: CONTROL OF
SYSTEM FROM EITHER OF TWO CONTROL SOURCES
Double
Check
Valve
To Trailer
Brakes
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