2003 FORD F750 brakes

System park
With both controls in for normal run modes, the parking brakes on both
tractor and trailer may be actuated by pulling the yellow control (parking
brake) out, which exhausts the air from the tractor spring brakes and
simultaneously causes the red control (trailer supply) to pop out,
applying the trailer brakes. This complies with federal regulations stating
one control must apply all the parking brakes on the vehicle.
Trailer charge
If both controls are out when parking the combination vehicle and it is
desired to recharge the trailer (leaving the tractor spring brakes
applied), the trailer air supply control may be pushed in, repressurizing
the trailer supply line. This mode could also be used to park a
combination vehicle with air actuated emergency brakes on the trailer to
provide demonstrated parking capability with tractor spring brakes only.
Automatic application
With both controls in (in the normal run configuration), if the supply
pressure to the push-pull valves is reduced to approximately 240 to 310
kPa (35-45 psi), the red control (trailer supply valve) must pop out,
applying the emergency or parking brakes on the trailer. If the red
control is held in manually and the pressure decreases to approximately
172 to 240 kPa (25-35 psi), a tripper piston within the MV-3 valve will
move upward. This will exhaust the trailer supply, causing the required
non-override feature. The yellow control (parking brake) will pop out at
approximately 138 to 207 kPa (20-30 psi).
Reservoir selection
The number one service reservoir will at all times be selected as the
primary supply source for the MV-3. This is accomplished automatically
by the function of the dual circuit supply valve contained in the body of
the MV-3. Only in the event of a pressure drop of more than 207 kPa (30
psi) below that of the number two service reservoir will the dual circuit
supply valve shuttle and establish the front service reservoir as the
supply.
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Exhaust brake (if equipped)
An exhaust brake is an optional
auxiliary braking system that assists
but does not replace the primary
service brake system. An on-off
switch on the instrument panel, in
combination with the accelerator
and clutch pedal switches, allows
the operator to make maximum use
of the exhaust brake in the
following conditions:
•off-highway driving
•mountain driving
•heavy traffic
•high speed highway driving
It is not available with automatic transmissions.
The exhaust brake is a butterfly
type valve mounted in the exhaust
pipe. When the operator’s foot is not
on the accelerator pedal and the
exhaust brake switch is in the ON
position, an air cylinder shuts the
butterfly valve, restricting the flow
of exhaust gases and retarding the
engine. This retarding action is
carried through the engine and drivetrain, slowing the vehicle and
reducing the need for frequent service brake applications.
Exhaust brakes are not intended for use as the primary braking system
during vehicle operation.
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Operation
Push the rocker switch up to turn
the exhaust brake on. The switch
will illuminate in the ON position.
Push the switch down to turn the
brake off.
Starting engine
Before starting the engine, make sure that the exhaust brake switch is in
the OFF position. Do not turn the exhaust brake on until the engine has
reached normal operating temperatures.
Driving downhill
While approaching a steep grade, make sure that the exhaust brake
switch is in the ON position. The exhaust brake actuates as soon as you
remove your foot from the accelerator pedal. While going down the
grade, use a low enough gear to descend safely with a minimum
application of the service brakes. As a general guideline, use the same
gear as you would to ascend the hill.
Before descending a hill or steep grade always select the proper gear. If
the transmission is taken out of gear while descending it is possible that
you will not be able to select another gear because of maximum RPM
being governed.
Make sure the engine speed does not exceed the maximum allowable
engine RPM. Exceeding the maximum allowable engine RPM will result
in damage to the engine. Apply the service brakes to reduce the engine
RPM or make a slower descent by using a lower gear.
The exhaust brake is not recommended for use on slippery or
low traction road surfaces. Under these conditions a loss of
vehicle control could possibly occur.
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Exhaust brake operating characteristics
When you remove your feet from both the accelerator and clutch pedals
and the exhaust brake switch is in the ON position, the exhaust brake is
activated. The following conditions should exist if the brake is operating
properly:
•A slight change in the sound of the engine when the exhaust brake is
activated.
•Exhaust smoke appears normal.
•Engine temperature remains in the normal operating range.
•Road speed usually decreases when the exhaust brake is applied
during a descent, except when the vehicle is carrying a heavy load or
the grade is extremely steep. In these instances, you may need to
apply the service brakes occasionally.
•During a descent, the tachometer usually shows a drop in RPM
depending on the grade and the vehicle load.
•Do not expect a retarding effect similar to sudden hard application of
the service brakes. The exhaust brake retards the vehicle with a
smooth braking effect.
•Depending on the grade and vehicle load, you may or may not feel the
retarding force acting against your body when the brake is applied.
The brake’s retarding force is actually preventing the vehicle from
going much faster.
Make sure the exhaust brake is turned off before shutting off the engine.
Installing an exhaust or auxiliary brake should never allow the
engine to exceed maximum governed speeds under any
conditions.
Air brake reservoir draining
Failure to drain air brake reservoirs can result in a reduction or
loss of braking ability due to fluid accumulation in the reservoir
and/or possible freeze-up during cold weather.
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The N (Neutral) position may also be used during stationary operation of
the Power Take-Off (PTO), if equipped.
Do not allow your vehicle to coast in N (Neutral). Engine
braking is not available in N (Neutral). Allowing your vehicle to
coast in N (Neutral) may result in loss of vehicle control and severe
internal transmission damage.
D (Drive—Normal driving position)
In this position, the transmission starts in first gear and automatically
shifts through second, third, fourth and fifth depending on load and
speed demands. When the vehicle is slowing down, the transmission will
automatically downshift. This range is used for highway driving under
normal conditions.
4 and 2 (Fourth and Second)
Use this position when road, load or traffic conditions make it desirable
to restrict the automatic shifting to a lower range. These ranges provide
greater engine braking than D (Drive). When conditions no longer
require these lower gears, shift back to D (Drive).
1 (First)
The transmission has to be manually shifted into 1 (First) and will not
shift into a higher gear. Use this position when pulling through mud or
snow, driving up steep grades, hauling extra heavy loads or where
maximum reduction is required.
Power take-off (PTO) operation with an Allison automatic
transmission (except MD applications and vehicles equipped with
a Caterpillar 3126E engine)
The power take-off can be operated while the vehicle is standing or
moving.
To engage the PTO, apply the brakes and shift to any gear other than N
(Neutral) - this stops the rotation of the PTO drive gear in the
transmission - then engage the PTO.
If engagement is prevented by the gear teeth not meshing properly,
release the brakes and allow the vehicle to creep slightly - or shift the
selector to N (Neutral) and then back in gear. The PTO should never be
engaged by clashing the gear teeth. This may damage the PTO unit and
the transmission PTO drive gear teeth. This could result in further
damage to the transmission and PTO.
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Ratio extender use
Low End
A two-speed axle can be used as a ratio-extender when split shifting is
not necessary. For low end use, just shift the axle into the LO to start
out, and shift to HI when the extra torque is no longer needed.
Transmission (5-speed) 1st 1st 2nd 3rd 4th 5th 6th
Two-speed Axle Axle
LowAxle High
High End
To use the two-speed axle as a high end ratio-extender, stay in the LO
range for normal upshifts and only shift the axle to HI on the freeway for
greater road speed.
Transmission (5-speed) 1st 2nd 3rd 4th 5th 6th
Speed
Axle
High Two-Speed Axle Low for Gradeability
DRIVING THROUGH WATER
Do not drive quickly through standing water, especially if the depth is
unknown. Traction or brake capability may be limited and if the ignition
system gets wet, your engine may stall. Water may also enter your
engine’s air intake and severely damage your engine.
If driving through deep or standing water is unavoidable, proceed very
slowly. Never drive through water that is higher than the bottom of the
hubs (for trucks) or the bottom of the wheel rims (for cars).
Once through the water, always try the brakes. Wet brakes do not stop
the vehicle as effectively as dry brakes. Drying can be improved by
moving your vehicle slowly while applying light pressure on the brake
pedal.
Driving through deep water where the transmission vent tube is
submerged may allow water into the transmission and cause
internal transmission damage. Have the fluid checked and, if
water is found, replace the fluid.
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Connecting the jumper cables
1. Position the vehicles so that they
do not touch one another.
2. Apply the parking brakes.
3. Switch off the engine and any
unnecessary electrical equipment.
4. Find the positive (+) terminal of
the discharged battery.
5. Using the jumper cables, connect
the positive (+) terminal of the
discharged battery to the positive
(+) terminal of the booster battery.
NOTE:In the illustration,
lightning bolts are used to
designate the assisting (boosting)
battery.
6. Connect one end of the cable to
the negative (-) terminal of the
booster battery and the other end to
a ground at least 12 inches from the
battery of the discharged vehicle. The vehicle frame is usually a good
ground.
7. Ensure that the jump leads are clear of moving parts of the engine,
and that the clamps from one cable do not touch the clamps on the
other cable.
8. Do not lean over the batteries when making the connections.
Do not connect the end of the second cable to the negative (-)
terminal of the battery to be jumped. A spark may cause an
explosion of the gases that surround the battery.
Jump starting
1. Start the booster vehicle and run the engine at moderately increased
speed.
2. After a few minutes, start the engine of the vehicle with the
discharged battery.
3. After starting, run the engine at about 1,000 RPM for 3–5 minutes.
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Do not operate the starter longer than 30 seconds. Wait at least
two minutes between starting attempts to allow the starter to
cool. If the engine does not start after several attempts, call for
road service.
Removing the jumper cables
1. Remove the ground connection
from the disabled vehicle first,
followed by the cable on the
negative (-) battery terminal of the
booster vehicle.
2. Remove the cable from the
positive (+) terminal of the
discharged battery and then from
the positive (+) terminal of the
booster battery.
3. After the disabled vehicle has
been started, allow it to idle for a
while so the engine can“relearn”its
idle conditions.
WRECKER TOWING
Always unload your vehicle before towing it. The recommended method
of towing is with the drive wheels off the ground.
Before towing, make sure:
•the parking brake is released.
•if air pressure has been lost, to release the brakes manually.
Improper towing of the vehicle will not allow sufficient lubrication of the
transmission which may cause serious damage to internal transmission
components. Always follow the outlined towing procedures.
•To tow a vehicle on the front wheels,the steering wheel must be
in the straight ahead position. Secure the steering wheel with a
holding device (such as provided by a towing company).
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