Bendix Commercial Vehicle Systems TP-3 User Manual

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Bendix® TP-3™ Tractor Protection Valve

SD-03-3652

TRACTOR
EMERGENCY
PORT

TRACTOR

SERVICE

PORT

PRELOAD

SPRING (2)

DIAPHRAGM

SEAT (9)

WASHER (8)

CAP SCREW (3)

TRAILER
EMERGENCY
PORT

TRAILER

SERVICE

PORT

EXTERIOR VIEW

INLET VALVE (4)

VALVE SPRING (6)

DIAPHRAGM (5)
O-RING (7)

RETAINING RING (1)

OLD REVISION TYPE TP-3
TRACTOR PROTECTION VALVE
OPENING PRESSURE
APPROXIMATELY 80 PSI

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SPRING (6)

DIAPHRAGM

SEAT (9)

DIAPHRAGM (5)

WASHER (8)

O-RING (13)

PLUNGER (3)
VALVE (4)

VALVE
RETAINER (10)

RETAINING

RING (14)

O-RING (12)

SEAT
O-RING (7)

RETAINING

RING (1)

CAP SCREW (3)

NEW REVISION TYPE TP-3
TRACTOR PROTECTION VALVE
OPENING PRESSURE
APPROXIMATELY 45 PSI

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FIGURE 1

DESCRIPTION

The TP-3™ (See Figure 1) tractor protection valve is used in
combination with the PP-3™ trailer supply valve on pre-121
tractors and the PP-7™ trailer supply valve on post-121
tractors. It contains a passage for trailer supply air and a
service line shut off valve. It is normally mounted behind the
cab with the delivery line from the trailer supply valve
connected into the tractor emergency port and a delivery
line from the brake valve connected to the tractor service
port. The trailer supply and service hoses are mounted in
their respective ports in the TP-3™ valve. (See Figure 2)

OPERATION

Air from the trailer supply valve passes through the
emergency ports of the TP-3™ valve to supply the trailer air
system and simultaneously exerts pressure on the end of
the plunger (3). Figure 3. TP-3™ valves manufactured prior to
June 1970 required approximately 80 psi on the plunger to

open the inlet valve (4) (See Figure 4) which opens the service
line shut off line. V alves manufactured after June 1970 require
approximately 45 psi to open the inlet valve. (Modification
kit 265066 is available to modify old revision TP-3™ valves to
the later revision 45 psi opening. Field maintenance kit
280858 contains the parts necessary to service both old
and new).

Whenever the pressure from the trailer supply valve drops
below 45 psi the TP-3™ valve will close the service line shut-off
valve.

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.

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FIGURE 2

COMPRESSOR

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PP-3

CONTROL

VALVE

CONTROL VALVE

NO. 1

RESERVOIR

TC-2

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TP-3

DOUBLE

CHECK

NO. 2

RESERVOIR

TRACTOR

PROTECTION

VALVE

BRAKE

VALVE

TRAILER

EMERGENCY

LINE

TRAILER

SERVICE LINE

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 TP-3
valve should be inspected every 6 months or 1500 operating
hours, whichever comes first, for proper operation. Should
the TP-3™ valve not meet the elements of the operational
tests noted in this document, further investigation and service
of the valve may be required.

OPERATING AND LEAKAGE CHECKS

1. Block and/or hold the vehicle by a means other than air
brakes during these tests. Place the trailer supply valve
in the emergency position and disconnect the trailer
supply and service couplings.

2. With tractor reservoirs charged to at least 100 psi make
and hold a full service brake application. Leakage at
either tractor hose coupling should not exceed a 1"
bubble in 5 seconds (100 SCCM).

3. Connect the trailer supply or emergency line hose
coupling and place the trailer supply valve in the “run”
position. Leakage at the “service” coupling should not
exceed a 1" bubble in 5 seconds (100 SCCM).

4. Connect the service coupling and make and hold a full
service brake application: Leakage at the diaphragm
end of the TP-3™ valve shall not exceed a 1" bubble in 3
seconds (175 SCCM).

NOTE: If the TP-3™ valve does not function as described or

if leakage is excessive, it is recommended that it
be returned to the nearest authorized Bendix parts

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outlet for factory rebuilt valve. If this is not possible,
the valve should be repaired using genuine Bendix
parts, in which case the following should prove
helpful.

REMOVING

Remove trailer hose assemblies from the TP-3™ valve.
Disconnect tractor service and supply lines and remove
the TP-3™ valve.

INST ALLING

When installing the TP-3™ valve, refer to Figure 2 for proper
connections along with the following explanation.

1. The delivery line from the trailer supply valve (PP-3™ or
PP-7™) is connected to the tractor emergency port of
the TP-3™ valve.

2. The delivery line from the brake valve (or double check
valve) is connected to the tractor service port of the TP-3
valve.

3. Trailer hose assemblies are installed in the trailer
emergency and trailer service ports of the TP-3™ valve.

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