5
2. Build system pressure to governor cut-out setting.
3. Make a service brake application with the foot valve and
have another person or persons observe the gauges.
When the front axle gauge reaches a 40 psi application
the rear axle gauge should read approximately 10-20
psi depending on rear axle relay valve differential. The
differential between the front axle and rear axles will
decrease as the application pressure is increased.
4. For vehicles without a front axle service ratio or limiting
valve with the trailer connected, push the trailer supply
valve in (applied position) and repeat check made in
Step 3. Gauges should read approximately equal
throughout range of service applications. For vehicles
with a BP-1
™
front valve push the trailer supply valve in
(applied position) and repeat check made in Step 3. When
the front axle gauge reads 20 psi, the rear axle gauge
should read approximately 40 psi. As system pressure
increases, the differential between the front and rear axles
diminishes.
5. Test drive the vehicle in a safe area at slow speed and
with the trailer supply valve in the bobtail position make
several brake applications to become familiar with the
brake characteristics prior to placing the unit back into
service.
PREVENTIVE MAINTENANCE
Important:
Review the Bendix Warranty Policy before
performing any intrusive maintenance procedures. A warranty
may be voided if intrusive maintenance is performed during
the warranty period.
No two vehicles operate under identical conditions, as a
result, maintenance intervals may vary. Experience is a
valuable guide in determining the best maintenance interval
for air brake system components. At a minimum, the BP-1
™
valve should be inspected every 6 months or 1500 operating
hours, whichever comes first, for proper operation. Should
be BP-1
™
valve not meet the elements of the operational
tests noted in this document, further investigation and service
of the valve may be required.
REMOVAL OF THE BP-1
™
REAR VALVE
FROM VEHICLE
1. Secure the vehicle on a level surface by means other
than the brakes.
2. Drain the air system completely making sure all reservoirs
are at atmospheric pressure.
3. Remove and identify the air lines from the BP-1
™
rear
valve. This valve is usually located along the frame rail
between the brake valve and the rear axle.
4. Remove the two bolts attaching the BP-1
™
rear valve to
the vehicle and move the valve to a bench.
5. Clean the exterior of the valve taking care to prevent
contaminates from entering the open ports of the valve.
DISASSEMBLY OF THE BP-1
™
REAR VALVE
(REFER TO FIGURE 4)
1. Remove the four Sems screws from the cover. Retain
the screws and the metal tag with ‘BP-1 Rear’ stamped
on it. Separate the cover from the body. Remove and
discard o-ring(7).
2. Remove the spring (8) from the I.D. of the inner piston,
remove the upper piston from the body and push the
inner piston out of the center of the upper piston.
3. Remove the lower piston from the body of the BP-1
™
rear valve and tip the piston over to remove the spring(6)
and the inlet/exhaust valve(5).
4. Remove the o-rings (1), (2), (3), (4) from the pistons.
CLEAN AND INSPECT
1. Wipe the interior of the cover, body, and the pistons
with a clean dry cloth to remove any contaminates.
2. Visually inspect all components for cracks, scoring, or
damage of any kind. If any of these conditions exist,
the valve should be replaced.
ASSEMBLY
1. Coat the bore surfaces of the cover, body, and upper
piston with a light coating of silicone lubricant.
2. Lubricate the six o-rings with the same material used in
Step 1.
3. Install the o-rings onto the pistons and the cover as shown
in Figure 4.
4. Install the inlet/exhaust valve into the bore of the lower
piston. Place the spring(6) on top of the inlet/exhaust
valve.
5. Install the inner piston into the bore of the upper piston
and then place the lower piston into the bottom of the
upper piston.
6. Place the piston assemblies into the body of the valve
and install the spring (8) into the I.D. of the inner piston
as shown in Figure 4.
7. Place the cover with o-ring(7). in place onto the body
with the supply port directly above the control port.
8. Install the four Sems screws and torque to 50-80 inch
pounds.
Note:
Be sure that the identification tag stamped ‘BP-1
Rear’ has been reinstalled on one of the screws.
9. Reinstall the BP-1
™
rear valve on the vehicle and
reconnect the airlines as identified in ‘Removal’
instructions.
10. Refer to section titled ‘Operational Checks’.
