BENDIX TC-4 MODULATING CONTROL VALVE User manual

®
SD-03-4503
Bendix®TC-4™Modulating Control Valve
FIGURE 1
FIGURE 2
TC-2™VALVE
EXHAUST
PORT
DELIVERY
PORT
SUPPLY PORT
DELIVERY
PORT
TW-1™VALVE
MANIFOLD
GAUGE
BRAKE
CHAMBERS
QR-1™
VALVE
E-3™BRAKE
VALVE
COMPRESSOR
GOVERNOR
TC-2™VALVE SV-1™
VALVE DS-1
TP-2™
VALVE
COUPLINGS
TRAILER
SERVICE
TRAILER
EMERGENCY
SPRING
BRAKES
QR-1™
VALVE
RELAY
VALVE
SINGLE CHECK
VALVE
SINGLE CHECK
VALVE
DRAIN COCK
SERVICE
RESERVOIR
DRAIN
COCK
SUPPLY
RESERVOIR
SAFETY VALVE
PARKING&
EMERGENCY
RESERVOIR
TYPICAL
PIPING
DIAGRAM

2
7LEVER
PIN9
8TORSION SPRING O-RING 15
PLUNGER 10
SHIM
12 GRADUATINGSPRING
16 O-RING
13 PISTON
BODY
PISTON RETURN SPRING 14
VALVE4
VALVESPRING5
MACHINESCREW
6DISC
5LOCKING
BUTTON
CAP NUT SEALING RING 2
CAP NUT 1
FIGURE 3

3
DESCRIPTION
The TC-4™modulating control valve is a cam operated,
graduating type control valve. The valve is used to control
theapplication andrelease ofspring brakeactuators, andis
generallymountedinthecab withineasy reachof thedriver.
Modulatedcontrol ofthe emergencybrakes (springbrakes)
iseffectedbymovingthevalve’sspringloadedlever.Moving
the lever against the resistance of the spring applies the
brakesand,allowing thevalvehandletoreturn, releasesthe
brakes.
When the valve is used for parking, the locking button is
moved into the locked position after the handle has been
moved to the “Brakes Applied” position. The lever is now
mechanically locked in position. To release the lever, the
leveris slightly depressed,the lockbuttonmoved outofthe
locked position and the lever returned to the “Brakes
Released”position.
Portingconsists of one (1)supply port, two (2)delivery and
two (2) exhaust ports.
OPERATION
Reference Figure 2, the TC-4™valve is generally used in
conjunctionwith a relayvalveto control theapplication and
releaseof the springbrakes.In atypicalsystem, the TC-4™
valve and the relay valve receive supply air from the
emergency/parkingreservoir.
RELEASED POSITION (Spring Brakes Released)
In the normal run position, air enters the supply port of the
TC-4™valve,flowsbytheopeninletvalveandoutthedelivery
port.Air flows to the service(control) port of therelayvalve
causing the relay valve to deliver air to the spring brakes,
holdingthemin the released position.
APPLYPOSITION (Spring BrakesApplied)
Movingthe lever to the applypositionallows the inlet valve
to close and the exhaust passage to open. This allows the
air being delivered to the service (control) port of the relay
valveto exhaust toatmosphere (through theexhaust of the
foot brake valve). With air exhausted from the service
(control) port of the relay valve, the relay valve responds,
exhaustingtheairfromthespringbrakes(allowingthebrakes
to apply).
With sufficient air pressure in the emergency/parking
reservoir, modulation of the spring brake application is
possible; the amount of braking force governed by the
positionoftheTC-4™valvelever.
With reference to Figure 2, note that the exhaust of the
TC-4™valveis connectedto a deliveryline of thefoot brake
valve. This prevents the compounding of spring brake and
service brake application forces on the slack adjusters.
PREVENTIVE MAINTENANCE
Important: Review the Bendix Warranty Policy before
performinganyintrusivemaintenanceprocedures.Awarranty
maybe voidedif intrusive maintenanceis performedduring
thewarranty period.
No two vehicles operate under identical conditions, as a
result, maintenance intervals may vary. Experience is a
valuableguideindeterminingthebestmaintenanceinterval
forair brake systemcomponents.At aminimum, theTC-4™
valveshouldbeinspectedevery6monthsor1500operating
hours,whichevercomes first, for proper operation. Should
the TC-4™valve not meet the elements of the operational
testsnotedinthisdocument,furtherinvestigationandservice
ofthe valvemay berequired.
Checkforproperoperationbeforeplacingvehicleinoperation.
OPERATING AND LEAKAGE TESTS
Ifvalve is to betestedon vehicle, block thevehiclewheels.
Build system pressure to approximately 100 psi and place
lever to “apply” position and observe that spring brakes
apply.
With lever in apply position, lock lever in place with locking
button.Coatexhaustportwithsoapsolution; leakageshould
not exceed a 1" bubble in less than 5 seconds.
(NOTE: If lineis connected toexhaustport, disconnect line
or remove pipe plug from other exhaust port.)
Excessiveleakagewouldindicateafaultyinletvalve.
Releaselockingbutton and place leverinrelease position;
observe that brakes fully release. Coat exhaust port with
soapsolution; leakageshould notexceeda 1"bubble innot
less than 5 seconds. Excessive leakage would indicate
exhaustvalveor lowero-ring leakage.(Iflineatexhaust port
wasdisconnected, connectline and/ortightenfitting orpipe
plug.)
Removedial; whilemaking afull footvalveapplication, coat
top of valve with soap solution. Leakage permitted is a 1"
bubble in not less than 5 seconds.
Excessiveleakage would indicate uppero-ringleakage. (If
lineis not connected toexhaustport, it will benecessaryto
apply 100 psi to the exhaust port to check for upper o-ring
leakage.)
Soap area around supply port cap nut to check for cap nut
o-ringleakage. No leakagepermitted.
Blow out or dry all soap solution and replace dial.
To check modulation of valve, it will be necessary to test
while vehicle is in motion. Select a suitable location to
performbrakingtest.Withvehicleinmotion,applytheTC-4™
valveseveraltimes.

NOTE: The valve is correctly modulating the brake
application.
If the valve does not function as described, or if leakage is
excessive,it isrecommended thatitbe replacedwith anew
orremanufacturedunitorrepairedwithgenuineBendix parts
availableat Bendix outlets.
REMOVING AND INSTALLING
REMOVING
Block and hold vehicle by means other than air brakes.
Drainall air brake system reservoirs.
Identify air lines to TC-4™valve to facilitate installation;
disconnect lines.
Removemounting screws,then valve.
INSTALLING
Cleanair lines to valve.
Mountvalve securely withtwo mounting screws.
Identify and connect air lines to valve.
DISASSEMBLY (Refer to Figure 3)
1. Removecap nut (1) and capnutsealing ring (2).
2. Remove inletvalve spring (3) andinlet valve (4).
3. Remove locking button (5) and rubber friction disc (6).
4. Marklever (7)in relationtobodyandtorsion spring(8) in
relation to handle so that proper position can be
determinedduring assembly.
5. Usinga smalldrift,carefullyremovepin (9),lever(7)and
spring(8).
6. Removeplunger (10),shims(11)(ifpresent),graduating
spring(12), piston (13) andpistonreturn spring (14).
7. Removeo-rings(15and16)fromplunger (10)andpiston
(13).
CLEANINGANDINSPECTION
Washallmetalpartsinmineral spirits.Wipeallrubber parts
dry.
Inspect all parts for signs of wear or deterioration; check
springs for cracks, corrosion or distortion. Inspect piston
and inlet and exhaust seat for nicks or burrs.
It is recommended that all rubber parts and any other part
showing signs of wear or deterioration be replaced.
ASSEMBLY
Prior to assembly, lubricate the piston, o-rings and body
bores with Dow Corning 55-M pneumatic grease (Bendix
Pc.No. 291126).
1. Installo-rings (15 &16) on plunger(10) and piston(13).
2. Installshims (11) and graduating spring (12).
3. Install piston (13) on plunger (10).
4. Install piston return spring (14) on piston; holding this
assembly vertical, place the body over the top of the
pistonassembly,then turn overletting the assemblyfall
into place.
5. Installthe torsionspring (8)over thelever(7) notingthat
partsareincorrectrelationto bodyaspreviouslymarked.
6. Place the ends of the torsion spring (8) in holes in the
body. Install pin (9) and center in place.
7. Checkfor correcthandle assemblyby notingthetorsion
spring and handle assembly will move the piston past
the inlet seat surface. (This can be seen by looking at
the supply port end of the valve.) If handle is not
assembled into body correctly, reassemble.
8. Installinlet valve(4) and inletvalve spring(3).
9. Install sealing ring (2) on cap nut (1); install cap nut
(Torque to50-100 inchpounds.)
10. Install disc (6) in locking button (5) and install button
intovalve.
11. Test valve as outlined in “Operating and Leakage Test”
section.
WARNING! PLEASE READ AND FOLLOW
THESE INSTRUCTIONS TO AVOID
PERSONAL INJURYOR DEATH:
When working on or around a vehicle, the following
general precautions should be observed at all times.
1. Park the vehicle on a level surface, apply the
parking brakes, and always block the wheels.
Always wear safety glasses.
2. Stop the engine and remove ignition key when
working under or around the vehicle. When
working in the engine compartment, the engine
should be shut off and the ignition key should be
removed. Where circumstances require that the
enginebe in operation, EXTREME CAUTIONshould
be used to prevent personal injury resulting from
contact with moving, rotating, leaking, heated or
electrically charged components.
3. Do not attempt to install, remove, disassemble or
assemble a component until you have read and
thoroughly understand the recommended
procedures. Useonly theproper toolsand observe
all precautions pertaining to use of those tools.
4. If the work is being performed on the vehicle’s air
brake system, or any auxiliary pressurized air
systems,makecertain to draintheair pressure from
all reservoirs before beginning ANY work on the
vehicle. If the vehicle is equipped with an AD-IS™
air dryer system or a dryer reservoir module, be
sure to drain the purge reservoir.

5. Following the vehicle manufacturer’s
recommendedprocedures, deactivate theelectrical
system in a manner that safely removes all
electrical power from the vehicle.
6. Never exceed manufacturer’s recommended
pressures.
7. Never connect or disconnect a hose or line
containing pressure; it may whip. Never remove a
component or plug unless you are certain all
system pressure has been depleted.
8. Use only genuine Bendix®replacement parts,
components and kits. Replacement hardware,
tubing, hose, fittings, etc. must be of equivalent
size, type and strength as original equipment and
be designed specifically for such applications and
systems.
9. Components with stripped threads or damaged
parts should be replaced rather than repaired. Do
not attempt repairs requiring machining or welding
unless specifically stated and approved by the
vehicle and component manufacturer.
10. Prior to returning the vehicle to service, make
certain all components and systems are restored
to their proper operating condition.
BW1566 © 2004 Bendix Commercial Vehicle Systems LLC. All rights reserved. 4/2004 Printed in U.S.A.