1999 GMC C-SERIES hood open

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2-43
When the handle is pulled out, the engine air intake
supply is closed off from the front scoop and an under
hood air supply is opened. This control is intended only
for use in cold weather (32
F (0
C) or below) where
snow and ice might plug the external intake.
At temperatures above 32
F (0
C), keep the control
handle pushed in.
NOTICE:
Operating this vehicle with the engine air control
on when outside temperatures are above 32
F
(0
C), could lead to costly repairs not covered by
your warranty. It will also degrade fuel economy
and the engine will not run smoothly.
Exterior Lamps
Headlamps
The lamp switches are on the left side of your
instrument panel.
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3-7
Ventilation Tips

Keep the hood and front air inlet free of ice, snow or
any other obstruction (such as leaves). The heater
and defogger will work far better, reducing the
chance of fogging the inside of your windows.

When you enter a vehicle in cold weather, turn the
blower fan to high for a few moments before driving
off. This helps clear the intake ducts of snow and
moisture and reduces the chance of fogging the
inside of your windows.

Keep the air path under the seats clear of objects.
This helps air to circulate throughout your vehicle.
The air vents are located in the center and on the sides of
your instrument panel. You can move the vents to direct
the flow of air or close the vents altogether. When you
close a vent, it will increase the flow of air coming out
of any vents that are open.
If your vehicle does not have air conditioning, there are
air vent controls located below the instrument panel.Audio Systems
Your Delco Electronics audio system has been designed
to operate easily and give years of listening pleasure.
You will get the most enjoyment out of it if you acquaint
yourself with it first. Find out what your Delco
Electronics system can do and how to operate all its
controls, to be sure you're getting the most out of the
advanced engineering that went into it.
Setting the Clock
While pressing the SET button, press the UP button
until the correct hour appears on the display and the
DOWN button until the correct minute appears on the
display. If you press and hold the UP/DOWN button,
hours or minutes will advance rapidly.
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5-18
Engine Overheating
You will find a coolant temperature warning gage on
your vehicle's instrument panel, as well as a LOW
COOLANT warning light. Your vehicle also has a
CHECK GAGES warning light on the instrument panel.
If Steam Is Coming From Your Engine
CAUTION:
Steam from an overheated engine can burn you
badly, even if you just open the hood. Stay away
from the engine if you see or hear steam coming
from it. Just turn it off and get everyone away
from the vehicle until it cools down. Wait until
there is no sign of steam or coolant before you
open the hood.
If you keep driving when your engine is
overheated, the liquids in it can catch fire. You or
others could be badly burned. Stop your engine if
it overheats, and get out of the vehicle until the
engine is cool.
NOTICE:
If your engine catches fire because you keep
driving with no coolant, your vehicle can be
badly damaged. The costly repairs would not be
covered by your warranty.
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5-19 If No Steam Is Coming From Your Engine
If you get an engine overheat warning but see or hear no
steam, the problem may not be too serious. Sometimes
the engine can get a little too hot when you:

Climb a long hill on a hot day.

Stop after high
-speed driving.

Idle for long periods in traffic.
If you get the overheat warning with no sign of steam,
try this for a minute or so:
1. If you have an air conditioner and it's on, turn it off.
2. Turn on your heater to full hot at the highest fan
speed and open the window as necessary.
3. If you're in a traffic jam, shift to NEUTRAL (N);
otherwise, shift to the highest gear while
driving
-- DRIVE (D) for automatic transmissions.
4. If climbing a hill, downshift to raise engine and
fan speeds.If you no longer have the overheat warning, you can
drive. Just to be safe, drive slower for about 10 minutes.
If the warning doesn't come back on, you can
drive normally.
If the warning continues, pull over, stop, and park your
vehicle right away.
If there's still no sign of steam, push down the
accelerator until the engine speed is about twice as fast
as normal idle speed for at least three minutes while
you're parked. If you still have the warning, turn off the
engine and get everyone out of the vehicle until it
cools down.
You may decide not to lift the hood but to get service
help right away.
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6-9
Checking Things Under the Hood
To tilt the hood forward, pull out on each of the hood
latches. If the hood is equipped with hood access panels,
make sure the panel latches are locked down before
rotating the hood open.
Then take the hand holds and pull the hood forward.
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7-20
(16) = Check spring-to-axle U-bolts and shackle bolts
for proper torque. See the service manual for torque
sequence and specifications. When parts are replaced,
the torque must be checked and adjusted more often
during the first 6,000 miles (10 000 km). Check torque
at 500 miles (800 km) and 2,000 miles (3 000 km) after
first use of parts.
(17) = Check complete exhaust system and cab areas
near the exhaust system for broken, damaged, missing or
out
-of-position parts. Also inspect for open seams,
holes, loose connections or other conditions which could
let exhaust fumes seep into the driver compartment.
Needed repairs should be made at once. To help
maintain system integrity, replace exhaust pipes
whenever a new muffler is put on.
(18) = Check all engine drive belts for cracks, fraying,
wear and proper tension. Adjust or replace as needed.
(19) = Check throttle linkage for damaged or missing
parts (including throttle return springs), interference or
binding. Fix any problems at once. Do not lubricate
accelerator and cruise control cables.
(20) = With the engine off and below normal operating
temperature, check to see that the thermostatically
controlled engine cooling fan can be rotated by hand on
viscous
-operated drives. Replace as needed.(21) = Check shields and underhood insulation for
damage or looseness. Adjust or replace as needed.
(22) = Lubricate caliper housing, caliper support spring
and caliper support key.
(23) = Wheel bearing service:

Grease type
-- Clean, inspect and lubricate with the
proper wheel bearing grease at designated intervals
or when hubs are removed. See ªRecommended
Fluids and Lubricantsº in the Index.

Oil
-filled type -- Some wheel bearings are lubricated
by rear axle lubricant. When you have oil
-filled
hubs, use lubricant identical to that used in your rear
axle. Lubricant change intervals are the same for
front and rear axles. However, you must maintain oil
level at the OIL LEVEL mark between change
intervals. See ªRecommended Fluids and
Lubricantsº in the Index.
(24) = Check the air intake system installation to see
that gaskets are seated properly and all hose
connections, fasteners and other components are tight.
For gasoline engines, also check to be sure the air
cleaner housing is properly seated, that the cover fits
tightly and that the wing nut is tight. Tighten
connections and fasteners or replace parts as required.
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7-27
Door Latches Check
Check that doors close, latch and lock tightly. Check for
broken, damaged or missing parts that might prevent
tight latching.
Hood Latches Check
Check that the hood closes firmly. Check for broken,
damaged, loose or missing parts that might prevent tight
latching. Make sure the secondary latch (if equipped)
keeps the hood from opening all the way when the
primary latch is released.
Fluid Leaks Check
Check for fuel, coolant, oil or other fluid leaks by
looking at the surface beneath the vehicle after it has
been parked for a while.
Underbody Inspection
Corrosive materials used for ice, snow removal and dust
control can collect on the underbody. If these materials
are not removed, accelerated corrosion (rust) can occur
on underbody parts such as fuel lines, frame, floor pan
and exhaust system. At least every spring, flush these materials from the underbody with plain water. Take
care to clean well any areas where mud and other debris
can collect. Sediment packed in closed areas of the
frame should be loosened before being flushed.
Engine Cover Check
Check that the cab's engine cover and seal (if equipped)
are not torn or damaged. Be sure that the cover is bolted
down firmly to the floor.
At Least Once a Year
Key Lock Cylinders Service
Lubricate the key lock cylinders with the lubricant
specified in Part C.
Underbody Flushing Service
At least every spring, use plain water to flush any
corrosive materials from the underbody. Take care to
clean thoroughly any areas where mud and other debris
can collect.
Tractor Protection (Breakaway) Valve Check
On air brake models, remove, disassemble, clean and
inspect the tractor protection (breakaway) valve.
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