
UNDER HOOD OVERVIEW - 7.3L
E330964E330964
Engine compartment fuse box. See Fuses (page 200). A
Engine oil dipstick. See Engine Oil Dipstick (page 224). B
Windshield washer fluid reservoir. See Washer Fluid Check (page 249). C
Automatic transmission fluid dipstick. See Automatic Transmission Fluid
Check (page 242). D
Engine coolant reservoir. See Engine Coolant Check (page 238). E
Engine oil filler cap. See Engine Oil Check (page 225). F
Brake fluid reservoir. See Brake Fluid Check (page 244). G
Power steering fluid reservoir. See Power Steering Fluid Check (page 245). H
Air cleaner assembly. See Changing the Engine Air Filter (page 230). I
223
Maintenance

1. Drive the vehicle until it reaches normal
operating temperature. This may take
up to 20 mi (30 km). Make sure that
the transmission fluid temperature
gauge on the instrument cluster is
within normal operating temperature
196–215°F (91–102°C) before
checking.
2. Make sure that your vehicle is on level
ground.
3. With the engine running, parking brake
engaged and your foot on the brake
pedal, move the gearshift lever through
all of the gear ranges. Allow sufficient
time for each gear to engage.
4. Make sure the parking brake is on. Make
sure the transmission is in park (P) or
neutral (N) and leave the engine
running.
5. Open the hood. See Opening and
Closing the Hood (page 220).
6. Remove the dipstick and wipe it with
a clean, lint-free cloth. See Under
Hood Overview (page 222).
7. Replace the dipstick and remove it
again to check the fluid level.
8. If the fluid level is correct, replace the
dipstick and make sure it is fully seated.
Note:If the fluid level is between the
maximum and minimum marks, the fluid
level is acceptable. Do not add fluid.Transmission Fluid Level
Low Fluid Level
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If the fluid level is at or below the minimum
mark, add fluid immediately. See
Automatic Transmission Fluid
Capacity and Specification (page 302).
Note:If there is no indication of fluid on the
dipstick, have your vehicle checked
immediately.
Correct Fluid Level
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Make sure that the fluid level is between
the maximum and minimum marks.
243
Maintenance

High Fluid Level
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Do not add fluid further than the maximum
mark. Fluid levels above the maximum
mark could cause shift or engagement
concerns and possible damage.
Note:An overheating condition can cause
high fluid levels.
Adding Transmission Fluid
Do not use supplemental transmission
fluid additives, treatments or cleaning
agents. The use of these materials could
affect transmission operation and result
in damage to internal transmission
components and could lead to
transmission damage that the vehicle
Warranty does not cover.
Use only recommended transmission fluid
that meets our specifications. See
Automatic Transmission Fluid
Capacity and Specification (page 302).
Note:Use of a non-approved automatic
transmission fluid could cause internal
transmission component damage.
If necessary, add fluid in 8 fl oz (250 ml)
increments through the filler tube until the
level is correct.
If an overfill occurs, remove excess fluid
and have your vehicle checked as soon as
possible.
BRAKE FLUID CHECK
WARNING: Do not use any fluid
other than the recommended brake fluid
as this will reduce brake efficiency. Use
of incorrect fluid could result in the loss
of vehicle control, serious personal injury
or death.
WARNING: Only use brake fluid
from a sealed container. Contamination
with dirt, water, petroleum products or
other materials may result in brake
system damage or failure. Failure to
adhere to this warning could result in the
loss of vehicle control, serious personal
injury or death.
WARNING: Do not allow the fluid
to touch your skin or eyes. If this
happens, rinse the affected areas
immediately with plenty of water and
contact your physician.
WARNING: The brake system
could be affected if the brake fluid level
is below the MIN mark or above the MAX
mark on the brake fluid reservoir.
244
Maintenance

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1. Park your vehicle on a level surface.
2. Look at the brake fluid reservoir to see
where the brake fluid level is relative
to the MIN and the MAX marks on the
reservoir.
Note:If the brake fluid level is between the
MIN and the MAX marks on the reservoir, it
is acceptable.
Note:If the brake fluid level is below the
MIN mark or above the MAX mark, have
your vehicle checked as soon as possible.
Note:To avoid fluid contamination, the
reservoir cap must remain in place and fully
tight, unless you are adding fluid.
Only use fluid that meets our
specifications. See Capacities and
Specifications (page 288).
Brake Fluid Service Interval
Brake fluid absorbs water over time which
degrades the effectiveness of the brake
fluid. Change the brake fluid at the
specified intervals to prevent degraded
braking performance.For detailed interval information, see
Scheduled Maintenance in your Owner's
Manual or your local maintenance guide.
POWER STEERING FLUID
CHECK
Check the power steering fluid. See
Scheduled Maintenance (page 319). If
adding fluid is necessary, use only
MERCON LV ATF
Check the fluid level when it is at ambient
temperature.
1. Check the fluid level in the reservoir. It
should be between the MIN and MAX
range. Do not add fluid if the level is
within this range.
2. If the fluid level is low, add fluid to bring
the fluid level up to between the MIN
and MAX range.
3. Switch the engine on.
4. While the engine idles, turn the steering
wheel left and right several times.
5. Switch the engine off.
6. Recheck the fluid level in the reservoir.
Do not add fluid if the level is between
the MIN and MAX range.
7. If the fluid is low, add the proper type
of fluid in small amounts, continuously
checking the level until it is between
the MIN and MAX range. See
Hydraulic Power Steering Fluid
Capacity and Specification (page
306). Be sure to put the cap back on the
reservoir.
245
Maintenance

Air Dryer
Climactic conditions affect performance
of desiccant or after-cooler type air dryers.
You must establish a maintenance
schedule for each specific operation.
The use of an air dryer on a vehicle does
not eliminate the need to drain the air
reservoirs periodically.
Inspect for moisture in the air system by
opening reservoirs, draincocks or valves
and checking for presence of water. The
presence of small amounts of water due
to condensation is normal and is not an
indication that the dryer is not functioning
properly.
Replace or rebuild the desiccant cartridge
when you determine that the desiccant is
contaminated and does not have adequate
water absorption capacity. The desiccant
change interval may vary. A general
recommendation is to replace the
desiccant every 12 months (yearly). If
experience has shown that extended or
shortened life has resulted for a particular
installation, then the yearly interval can be
increased or decreased accordingly.
Draining the Air Brake Reservoir
WARNING: 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.
Completely drain all the air brake reservoirs
daily by opening the draincock at the ends
of the tanks. (Where accessible.
Pull-chains are used when the drains are
undercab or otherwise inaccessible.) Close
the draincock after draining. Manually drainany air tanks equipped with automatic
moisture ejector valves, as required, to
maintain a dry air system. Contact an
authorized dealer if you are unsure of the
air reservoir locations or the draining
procedure.
Hydraulic Brakes
Establish a regular schedule for periodic
cleaning, lubrication and adjustment
inspection based on vehicle use. Exact
maintenance intervals are difficult to
predetermine due to vehicle applications
and operating conditions. If you are
uncertain of the proper schedule for your
vehicle, contact an authorized dealer.
Regular inspections should include:
• Checking the brake lining (every service
interval). Establish inspection intervals
that provide for lining replacement
before damage to the disc occurs.
Excessive lining wear may expose the
backing plate to the disc causing
scoring of the disc faces. A qualified
technician should perform this
257
Maintenance

inspection and keep to instructions
provided by the service manual.
Hydraulic brake systems are
power-assisted. There is a great
reduction in braking capabilities
without engine assist.
• Proper fluid level. The level should be
at the bottom edge of the ring on each
reservoir fill port. Do not fill the master
cylinder to the top of the reservoir. If
fluid level requires attention to
maintain a proper master cylinder level,
this is an indication of either severe
operation (pad wear) or fluid leakage.
A more frequent and thorough brake
inspection is required.
• Brake lines, hoses and fittings. Repair
or replace brake line tubes, hoses or
fittings as required. Inspect these
components every 4,000 mi
(6,000 km) for the following.
• Lines for kinks, dents, corrosion or
rupture.
• Hoses for abrasions, kinks, soft
spots or rupture, collapse, cracks,
twists or loose frame supports.
When replacing a hose, be sure
there is adequate clearance to the
hose to avoid an abrasion to the
new hose.
• All connections for leaks.
Driveline Parking Brake
WARNING: Use wheel chocks and
exercise caution when inspecting under
the vehicle. A vehicle roll-away could
result in property damage, personal injury
or death.
A qualified technician should adjust the
parking brake and keep to the instructions
in the service manual.
AXLE INSPECTION
Front Axle
Maintaining the front axle alignment to
specifications is very important. A qualified
technician should check and maintain the
alignment.
Regular inspections should include:
• Toe-in inspection and adjustment (if
necessary), particularly with radial
tires.
• Checking for proper tightness of axle
mounting U-bolt nuts, attaching or
mounting bolts and nuts.
• Checking the axle for damage, binding,
worn parts and adequate lubrication.
• Checking the kingpins for excessive
wear. Also, perform this check during
other scheduled maintenance, for
example as tire rotation or service,
wheel bearing service and alignment.
See the workshop manual for proper
procedures.
Toe-in
It is essential to maintain correct toe-in
and tire pressure for optimum tire wear.
Inspecting steer axle tires in the first
3,000–10,000 mi (5,000–16,000 km)
generally shows 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, there can be a
left-to-right steer tire tread life differential
up to 40% depending on routes and other
variables.
258
Maintenance

• For proper suspension alignment.
Maintain proper alignment at all times.
• U-bolts. After the chassis has been
operating under load for 1,000 mi
(1,600 km) or six months (whichever
comes first), the U-bolt nuts must be
re-torqued. Re-torque the U-bolt nuts
every 37,000 mi (60,000 km)
thereafter. Clean and lubricate the
U-bolt and nut threads and seats to
make sure a like new condition when
re-torqueing. See Spring U-Bolt
Check (page 260).
FRAME AND TOW HOOK
INSPECTION
Your vehicle's chassis is manufactured
with frame rails of either HSLA steel or
heat-treated steel. Handle each in a
specific manner to make sure maximum
service life. Consult the service manual or
an authorized dealer before attempting
frame repair or modification.
It is important, particularly on vehicles that
use tow hooks frequently, to inspect the
front and rear tow hooks for damage or a
loose mounting.
REAR AXLE FLUID CHECK
Your rear axle may have an optional
synthetic lubricant that allows the use of
extended service intervals. A tag on the
filler plug identifies the use of the synthetic
lubricant.
Only use a lubricant that meets
manufacturer specifications. Use of a
non-approved rear axle lubricant may
cause internal axle component damage.
See Rear Axle Fluid Capacity and
Specification (page 305).
Checking the Fluid Level
1. Park your vehicle on level ground.2. Set the parking brake and shift into
position neutral (N) or park (P). Turn
the engine off.
3. Clean any dirt from around the axle
filler plug.
4. Remove the filler plug and inspect the
lubricant level. It should be at the
bottom of the filler plug opening.
5. Add lubricant, if necessary, through the
filler plug opening.
6. Clean and install the filler plug securely.
Changing the Fluid
Note:Drain the rear axle while the lubricant
is warm.
1. Park your vehicle on level ground.
2. Set the parking brake and shift into
position neutral (N) or park (P). Turn
the engine off.
3. Clean any dirt from around the axle
filler and drain plugs.
4. Remove the filler and drain plugs. Drain
the lubricant into a suitable container.
Dispose of all used automotive fluids
in a responsible manner following your
local authorized standards.
5. Clean and install the drain plug
securely.
6. Add lubricant through the filler plug
opening.
7. Clean and install the filler plug securely.
SPRING U-BOLT CHECK
Check and tighten the U-bolt nuts after
your vehicle has been operated under load
for 1,000 mi (1,600 km) or six months,
whichever occurs first.
Check and tighten the U-bolt nuts every
37,000 mi (60,000 km).
Check and tighten the U-bolt nuts with
your vehicle at curb height and unloaded.
260
Maintenance

• With your foot on the brake, shift
through all the gears while the engine
is running.
• We recommend that you change the
engine oil before you use your vehicle
again.
Fuel system
• Fill the fuel tank with high-quality fuel
until the first automatic shutoff of the
fuel pump nozzle.
Cooling system
• Protect against freezing temperatures.
• When removing your vehicle from
storage, check coolant fluid level.
Confirm that there are no cooling
system leaks and that fluid is at the
recommended level.
Disconnecting Your 12 Volt Battery
• Check and recharge as necessary. Keep
connections clean.
• If storing your vehicle for more than 30
days without recharging the battery,
we recommend that you disconnect
the battery cables to maintain battery
charge for quick starting.
Note:It is necessary to reset memory
features if you disconnect the battery
cables.
Brakes
• Make sure the brakes and parking brake
release fully.
Tires
• Maintain recommended air pressure.
Miscellaneous
• Make sure all linkages, cables, levers
and pins under your vehicle are covered
with grease to prevent rust.
• Move vehicles at least 25 ft (7.5 m)
every 15 days to lubricate working parts
and prevent corrosion.
Removing Vehicle From Storage
When your vehicle is ready to come out of
storage, do the following:
• Wash your vehicle to remove any dirt
or grease film build-up on window
surfaces.
• Check windshield wipers for any
deterioration.
• Check under the hood for any foreign
material that may have collected
during storage such as mice or squirrel
nests.
• Check the exhaust for any foreign
material that may have collected
during storage.
• Check tire pressures and set tire
inflation per the Tire Label.
• Check brake pedal operation. Drive
your vehicle 15 ft (4.5 m) back and
forth to remove rust build-up.
• Check fluid levels (including coolant,
oil and gas) to make sure there are no
leaks, and fluids are at recommended
levels.
• If you remove the battery, clean the
battery cable ends and check for
damage.
Contact an authorized dealer if you have
any concerns or issues.
268
Vehicle Care