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Releasing spring brake with air pressure
The air system in all vehicles with spring-actuated rear wheel parking
brakes is equipped with a tank valve located on the supply or service air
tank for connection to an outside air supply. The valve permits the
system to be recharged with air from an outside source, releasing the
spring-actuated parking brakes. The vehicle may then be towed in an
emergency.
An outside air source can be used only if the protected system is in
operating condition. If air pressure cannot be restored in the protected
air system, the spring-actuated brakes must be released manually.
Releasing spring brake manually
Do not attempt to disassemble the parking brake chamber under
any circumstances. The high spring load may cause serious
injury if the chamber clamps are removed.
If air pressure is released from the spring brake chamber the power
spring applies the brake and, unless air pressure can be re-established,
the spring brake must be released as follows in order to move the
vehicle.
Block the wheels to prevent the vehicle from moving.
Unexpected and possibly sudden vehicle movement may occur if
these precautions are not taken.
Impact wrenches should not be used as they may damage the piston and
prevent proper caging of the spring. Do not apply more than 68 Nm (50
lb-ft) torque to the release bolt nut.
1. Remove the stud tool and nut
from the carrying pocket on the
brake chamber assembly.
2. Remove the access plug from the
end of the spring chamber.
3. Insert the release stud through
the opening in the chamber and into
the spring pressure plate.
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USA English(fus)
Driving
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Check to make sure that the axle mounting U-bolt nuts, attaching or
mounting bolts and nuts are securely tightened. Regularly check front
axle for damage, binding, worn parts and adequate lubrication.
At regular intervals, or during other scheduled maintenance, (tire
rotation/service, wheel bearing service, alignment, etc.) the kingpins
should be checked for excessive wear. Refer to the service manual for
proper procedures.
Toe-in setting - general inspection
Inspecting steer axle tires in the first 4,800–16,000 service km
(3,000–10,000 service miles) will generally show if tires are wearing
normally.
Rapid outside shoulder wear on both tires indicates too much toe-in.
Rapid inside shoulder wear on both tires indicates too much toe-out. In
P&D-type service, which includes school buses, left-to-right steer tire
tread life differentials up to 40% can be observed depending on routes
and other variables.
Follow the tire manufacturer’s recommended cold inflation pressure for
the tire size, load range (ply rating) and steer axle loading typical for
their operation (each steer axle tire will equal
1⁄2steer axle loading).
Special applications may warrant a setting based on past experience with
the type of tire operating loads and conditions. Radial tires are more
sensitive to toe-in setting than bias ply tires. While not insensitive to
vehicle alignment, fine tuning school bus alignment to line-haul truck
standards will not drastically improve tire tread life.
It is essential that correct toe-in and tire pressure be maintained for
optimum tire wear.
Rear axle - general inspection
Check to make sure that the axle mounting U-bolts, attaching or
mounting bolts and nuts are securely tightened. Refer toU-bolt nut
torque chartin this chapter. Regularly check the rear axle for damaged,
binding or worn parts.
NoSpin Detroit Locker positive locking differential
Vehicle equipped with this type differential have the operator’s manual
supplied with the vehicle. Refer to this manual for maintenance checks.
Brake system - general inspection
Your vehicle is equipped with non-asbestos brake linings. However,
exposure to excessive amounts of brake material (whether asbestos or
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Supplement
USA English(fus)
Maintenance and specifications
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•Check that torque rod mounting fasteners are tight.
•Check to be sure the suspension alignment is maintained at all time.
•Check U-bolts after the chassis has been operating under load for
1,600 km (1,000 miles) or six months, whichever comes first, the
U-Bolt nuts must be re-torqued. The U-Bolt nuts thereafter must be
re-torqued every 58,000 km (36,000 miles). The U-Bolt and nut
threads and seats should be cleaned and lubricated to assure a“like
new”condition when re-torquing.
Note:See theU-Bolt Nut Torquechart later in this section.
Supporting your vehicle for service
When performing service repairs on your vehicle, first prepare the
vehicle by doing the following:
1. Park the vehicle on a level concrete floor.
2. Set the parking brake and block the wheels to prevent the vehicle
from moving.
3. Select a jack (floor jack preferred) with a rated capacity sufficient to
lift and hold up the vehicle.
4. Raise the vehicle with the jack applied to the axle(s). DO NOT use the
bumper as a lifting point.
5. Support the vehicle with floor stands under the axle(s). If the axle or
the suspension are being serviced, support the vehicle with floor stands
under the frame side-members, preferably between the axles.
Do not use a jack when working under a vehicle. It may give
way, causing the vehicle to fall and result in property damage,
personal injury or death. Always use floor stands to support the
vehicle.
FRAME AND TOW HOOKS
Your vehicles chassis is manufactured with frame rails of either mild
carbon steel, or HSLA steel. Each must be handled in a specific manner
to assure maximum service life. Before attempting frame repair or
modification, consult the service manual or your dealer.
It is important, particularly on vehicles where the tow hooks are used
frequently to inspect the front and rear tow hooks for damage or a loose
mounting.
2004 F650/750(f67)
Supplement
USA English(fus)
Maintenance and specifications
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Changing wheel types
Consult your dealer or wheel/rim distributor before attempting any wheel
or fastener changes.
Use only the same type and style wheels and mounting hardware
to replace original parts. Failure to do so may result in an
assembly that looks fine, but does not fit together properly. This could
possibly cause wheel or fastener failures which could result in property
damage, personal injury or death.
Do not attempt to mix stud-piloted wheels or fasteners with
hub-piloted wheels or fasteners.
Do not change from aluminum wheels to steel wheels or
vice-versa without changing the mounting hardware required or,
with flange-nut mounting systems, changing the hub and stud
assembly.
WHEEL NUT TORQUE
Size Nut mountingTorque
N.m. ft. lbs.
22 mm Flange 610–678 450–500
Note:Do not use lubrication on dry threads. Where excessive corrosion
exists, a light coat of lubricant on the first three threads of the stud bolt
is permitted. Keep lubricant away from:
•Hex nut and rim clamp contact surfaces.
•Cap nut ball face and ball seat on the disc wheel.
•Flange nut washer surface and flat on the disc wheel.
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USA English(fus)
Maintenance and specifications
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