1999 CHEVROLET SILVERADO cooling

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2-75
The anti-lock brake system warning light should come
on briefly when you turn the ignition key to RUN. If the
light doesn't come on then, have it fixed so it will be
ready to warn you if there is a problem.
Engine Coolant Temperature Gage
This gage shows the engine
coolant temperature.
It also provides an indicator of how hard your vehicle is
working. During a majority of the operation, the gage
will read 210
F (100
C) or less. If you are pulling a
load or going up hills, it is normal for the temperature to
fluctuate and approach the 250
F (122
C) mark. If the
gage reaches the 260
F (125
C) mark, it indicates that
the cooling system is working beyond its capacity.The ªProblems on the Road,º section of this manual
shows what to do. See ªEngine Overheatingº in
the Index.
Transmission Temperature Gage
(If Equipped)
If your vehicle has a heavy
duty automatic
transmission, you will have
a transmission temperature
gage.
When your ignition is on, the gage shows the
temperature of the transmission fluid. The normal
operating range is from 100
F (38
C) to about
265
F (130
C).

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NOTICE:
If you keep driving your vehicle with the
transmission TRANS HOT...IDLE ENGINE
message displayed, you can damage the
transmission. This could lead to costly repairs
that may not be covered under your warranty.
The following situations can cause the transmission to
operate at higher temperatures:

Towing a trailer

Hot outside air temperatures

Hauling a heavy load

Low transmission fluid level

High transmission fluid level

Restricted air flow to the radiator and the auxiliary
transmission oil cooler (if equipped).
A temporary solution to hotter transmission operating
temperatures may be to let the transmission cool down.
If the transmission is operated at higher temperatures on
a frequent basis, see ªScheduled Maintenanceº in the
Index for the proper transmission maintenance intervals.
LOW COOLANT
This message is displayed
when the cooling system is
low on coolant.
The engine may overheat. See ªEngine Coolantº in the
Index and have your vehicle serviced as soon as
you can.
CHECK COOLANT TEMP
This message is displayed
when the cooling system
temperature gets hot.
Check the coolant temperature gage and the coolant
level. See ªEngine Coolantº and ªEngine Coolant
Temperature Gageº in the Index. SeeªEngine
Overheatingº in the Index for further information.

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2-85 ENGINE OVERHEATED
This message is displayed
when the cooling system
temperature gets too hot.
This message will be displayed after the air conditioning
system has automatically turned off for the engine
coolant protection mode. SeeªEngine Overheatingº in
the Index for further information.
REDUCED ENGINE POWER
(V8 Gasoline Engines Only)
This message is displayed
when the cooling system
temperature gets too hot and
the engine further enters
the engine coolant
protection mode.
SeeªEngine Overheatingº in the Index for
further information.
CHECK ENG OIL PRESSURE
This message is displayed
when the engine oil pressure
is low.
See ªOil Pressure Gageº in the Index for
more information.
CHECK ENG OIL LEVEL
(Gasoline Engine)
This message is displayed
when the engine oil level
is low.
See ªEngine Oilº in the Index on how to check the oil
level and for what type of oil to add.

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The system will automatically switch to the recirculation
mode to lower the system load and improve interior
comfort. The OUTSIDE AIR and RECIRCULATION
button LEDs will not change. The system will return to
the OUTSIDE AIR function when the system load
is reduced.
A/C: Press this button to turn the air conditioning
on and off. The system will cool and dehumidify the air
inside the vehicle when the A/C light is on.
Air conditioning will be automatically disabled when
the outside temperature drops below a level at which air
conditioning is ineffective.
Air Conditioning
On hot days, open the windows long enough to let hot
air inside escape. This reduces the time it takes for your
vehicle to cool down. Then keep your windows closed
for the air conditioner to work its best.
The RECIRCULATION button, below the fan knob,
allows the air inside your vehicle to be recirculated. This
setting helps to maximize your air conditioner's
performance and your vehicle's fuel economy. This
setting also cools air the fastest and can be used to keep
unwanted odors and/or dust from entering the vehicle.
When using the air conditioner, turn off theRECIRCULATION button after the vehicle reaches a
comfortable interior temperature. When the right knob
on the control panel is between HEATER and
DEFROST, the recirculation feature will not function to
reduce window fogging.
The A/C button, below the mode knob, allows the air
coming into your vehicle to be cooled. This setting is
useful for normal cooling on hot days. When you use
A/C with the RECIRCULATION button pushed in, turn
off recirculation as soon as the vehicle reaches a
comfortable interior temperature.
Maximum air conditioning performance is obtained by
pressing the A/C button, the RECIRCULATION button
and turning the temperature knob fully counterclockwise
to the blue area. This setting also cools air the fastest.
After the vehicle's interior reaches a comfortable
temperature, press the OUTSIDE AIR button to place
the air conditioning system in the normal mode.
Passenger Compartment Air Filter (If Equipped)
Your vehicle may be equipped with a passenger
compartment air filter, which filters outside air entering
the vehicle. For information on replacing the filter see
ªPassenger Compartment Air Filterº in the Index.

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If your vehicle is equipped with heated outside rearview
mirrors, the rear window defogger button will activate
the rear window defogger and the heated outside
rearview mirrors.
Do not attach a temporary vehicle license, tape or decals
across the defogger grid on the rear window.
NOTICE:
Don't use a razor blade or something else sharp
on the inside of the rear window. If you do, you
could cut or damage the warming grid, and the
repairs wouldn't be covered by your warranty.
Ventilation System
For mild outside temperatures when little heating or
cooling is needed, use VENT to direct outside air
through your vehicle. Air will flow through the
instrument panel outlets.
Your vehicle's ventilation system supplies outside air to
the inside of your vehicle when it is moving. With the side
windows closed, air will flow into the front air inlet grilles,
through the vehicle, and out the air exhaust valves.Outside air will also enter the vehicle when the heater or
the air conditioning fan is running, unless you have the
RECIRCULATION button pushed in. For more
information on the RECIRCULATION button, see ªAir
Conditioningº earlier in this section.
Your vehicle has air
outlets in the center and
on the sides of your
instrument panel.
You can turn the outlets from side
-to-side or up and
down to direct the flow of air. The left driver and
passenger outlets on vehicles equipped with air
conditioning have shut off knobs. Turn the knob to the
left to shut off air flow and turn the knob to the right to
allow air flow. When you close an outlet, it will increase
the flow of air coming out of any outlets that are open.
The center outlet does not completely shut off airflow.

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4-30 After Off-Road Driving
Remove any brush or debris that has collected on the
underbody, chassis or under the hood. These
accumulations can be a fire hazard.
After operation in mud or sand, have the brake linings
cleaned and checked. These substances can cause
glazing and uneven braking. Check the body structure,
steering, suspension, wheels, tires and exhaust system
for damage. Also, check the fuel lines and cooling
system for any leakage.
Your vehicle will require more frequent service due to
off
-road use. Refer to the Maintenance Schedule for
additional information.
Driving at Night
Night driving is more dangerous than day driving. One
reason is that some drivers are likely to be impaired
-- by
alcohol or drugs, with night vision problems, or by fatigue.

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Keep your vehicle in good shape. Check all fluid
levels and also the brakes, tires, cooling system and
transmission. These parts can work hard on
mountain roads.

Know how to go down hills. The most important
thing to know is this: let your engine do some of the
slowing down. Shift to a lower gear when you go
down a steep or long hill.
CAUTION:
If you don't shift down, your brakes could get so
hot that they wouldn't work well. You would then
have poor braking or even none going down a hill.
You could crash. Shift down to let your engine
assist your brakes on a steep downhill slope.
CAUTION:
Coasting downhill in NEUTRAL (N) or with the
ignition off is dangerous. Your brakes will have to
do all the work of slowing down. They could get so
hot that they wouldn't work well. You would then
have poor braking or even none going down a hill.
You could crash. Always have your engine running
and your vehicle in gear when you go downhill.

Know how to go uphill. You may want to shift down
to a lower gear. The lower gears help cool your engine
and transmission, and you can climb the hill better.

Stay in your own lane when driving on two
-lane
roads in hills or mountains. Don't swing wide or cut
across the center of the road. Drive at speeds that let
you stay in your own lane.

As you go over the top of a hill, be alert. There could be
something in your lane, like a stalled car or an accident.

You may see highway signs on mountains that warn of
special problems. Examples are long grades, passing or
no
-passing zones, a falling rocks area or winding
roads. Be alert to these and take appropriate action.

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CAUTION:
It can be dangerous to get out of your vehicle if
the shift lever is not fully in PARK (P) with the
parking brake firmly set. Your vehicle can roll.
If you have left the engine running, the vehicle
can move suddenly. You or others could be
injured. To be sure your vehicle won't move, even
when you're on fairly level ground, use the steps
that follow.
Always put the shift lever fully in PARK (P) with
the parking brake firmly set.
If the transfer case on four-wheel drive vehicles is
in NEUTRAL (N), your vehicle will be free to
roll, even if your shift lever is in PARK (P). So, be
sure the transfer case is in a drive gear
-- not in
NEUTRAL (N).
When You Are Ready to Leave After
Parking on a Hill
1. Apply your regular brakes and hold the pedal down
while you:

Start your engine;

Shift into a gear; and

Release the parking brake.
2. Let up on the brake pedal.
3. Drive slowly until the trailer is clear of the chocks.
4. Stop and have someone pick up and store the chocks.
Maintenance When Trailer Towing
Your vehicle will need service more often when you're
pulling a trailer. See the Maintenance Schedule for more
on this. Things that are especially important in trailer
operation are automatic transmission fluid (don't
overfill), engine oil, axle lubricant, belt, cooling system
and brake system. Each of these is covered in this
manual, and the Index will help you find them quickly.
If you're trailering, it's a good idea to review these
sections before you start your trip.
Check periodically to see that all hitch nuts and bolts
are tight.