cooling GMC SONOMA 1999 Owner's Manual

Service Station Guide
Oil Viscosity
Engine Oil
See Section 6
Engine Oil Dipstick
See Section 6Fuel
Use unleaded gas only,
87 Octane or higher.
See Section 6
Cooling System
See Section 5
Hood Release
See Section 6
Windshield Washer
Fluid
See Section 6
Tire Pressure
See Section 6
Spare Tire Pressure
See Sections 5, 6
Battery
See Section 6

For
a More
Detailed Look at
What's Under the Hood
See Section 6

3-2
Comfort Controls
With these systems, you can control the heating, cooling
and ventilation in your vehicle.
Standard Climate Control System
Fan Control
The knob on the left side of the heating system control panel
controls the fan speed. To increase airflow, turn the knob
clockwise. To decrease airflow, turn it counterclockwise.
Temperature Knob
The middle knob on the control panel lets you select
the relative temperature of the air flowing into the
passenger area of your vehicle. Turn the knob clockwise
toward the red area for warmer air. Turn the knob
counterclockwise toward the blue area for cooler air.Mode Knob
The right knob on the control panel allows you to
choose the direction of air delivery.
OFF: This setting turns the system off. Some outside
air will still enter the vehicle whenever the vehicle is
moving forward.
VENT: This setting directs most of the air through
the instrument panel outlets and a small amount through
the floor outlets.
BI-LEVEL: Air is delivered through the heater
floor outlets as well as the instrument panel outlets.
HEATER: This setting directs most of the
warmed air through the heater floor outlets and some
air through the windshield defroster outlets.
BLEND: Airflow is divided equally between the
heater floor outlet and the windshield defroster outlets.
DEFROST: This setting directs most air through
the windshield defroster outlets and some through the
heater outlets.

3-3 Optional Climate Control System
Fan Control
The knob on the left side of the heating system
control panel controls the fan speed. To increase airflow,
turn the knob clockwise. To decrease airflow, turn
it counterclockwise.
Temperature Knob
The middle knob on the control panel lets you select
the relative temperature of the air flowing into the
passenger area of your vehicle. Turn the knob clockwise
toward the red area for warmer air. Turn the knob
counterclockwise toward the blue area for cooler air.Mode Knob
The right knob on the control panel allows you to
choose the direction of air delivery.
OFF: This setting turns the system off. Some outside
air will still enter the vehicle whenever the vehicle is
moving forward.
MAX A/C: This setting provides maximum cooling
with the least amount of work. MAX A/C recirculates
much of the air inside your vehicle so it cools quickly.
This setting directs most of the air through the
instrument panel vents and a small amount through
the floor vents.
A/C: This setting cools the air entering your vehicle and
directs most of the air through the instrument panel
vents and a small amount through the floor vents.
BI-LEVEL A/C: This setting cools the air
entering your vehicle and directs it through the heater
floor outlets as well as the instrument panel outlets.
VENT: This setting directs most of the air through
the instrument panel outlets and a small amount through
the floor outlets. The air conditioning compressor is not
working when VENT is selected.

3-4
HEATER: This setting directs most of the
warmed air through the heater floor outlets and some air
through the windshield defroster outlets.
BLEND: Airflow is divided equally between the
heater floor outlet and the windshield defroster outlets.
DEFROST: This setting directs most air through
the windshield defroster outlets and some through the
heater outlets.
Air Conditioning (If Equipped)
On hot days, open the windows long enough to let hot
inside air 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.
For quick cool
-down on very hot days, use MAX A/C
with the temperature knob turned counterclockwise.
This setting should be used to keep odors and/or dust
from entering the vehicle. For normal cooling on
hot days, use A/C with the temperature knob
turned counterclockwise.On cool but sunny days, use BI
-LEVEL A/C to deliver
warm air to the floor and cooler air to the instrument
panel outlets.
If you have the VORTEC 4300 V6 engine, when the
air conditioner is on, you may sometimes notice slight
changes in your vehicle's engine speed and power. This
is normal because the system is designed to cycle the
compressor on and off to keep the desired temperature.
Heating
The heater works best if you keep your windows closed
while using it. On cold days, use HEATER with the
temperature knob turned clockwise. BLEND is useful in
cool weather when you have fog or ice on the
windshield or side windows.
If you use the optional engine coolant heater before
starting your engine, your heating system will produce
warmer air faster to heat the passenger compartment in
cold weather. See ªEngine Coolant Heaterº in the Index.

3-5 Defogging and Defrosting
On cool, humid days, use BLEND to keep the
windshield and side windows clear.
Use DEFROST to remove fog or ice from the
windshield quickly in extreme humid or cold conditions.
Turn the temperature knob clockwise and turn the fan
control toward high.
If you have the heated outside mirror feature, you can
use it to defog or defrost your outside mirrors. For more
information, see ªHeated Outside Mirrorsº in the Index.
Ventilation System
For mild outside temperatures when little heating or
cooling is needed, use VENT to direct outside air
through your vehicle. Airflow is through the instrument
panel outlets.
Your vehicle's ventilation system supplies outside air to
the inside of your vehicle when it is moving. When the
vehicle is not moving, you can get outside air to flow
through by selecting any mode and any fan speed.
You will find air outlets in the center and on the sides of
your instrument panel.
You can direct the airflow side
-to-side by moving the
thumbwheel located in the center of the vent. The vent
can be tilted up and down also. To control the amount
of airflow through the outlets, move the thumbwheel
below the vent.

4-26 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.
Here are some tips on night driving.

Drive defensively.

Don't drink and drive.

4-35

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.

4-54 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.

5-
5-1
Section 5 Problems on the Road
Here you'll find what to do about some problems that can occur on the road.
5
-2 Hazard Warning Flashers
5
-2 Other Warning Devices
5
-3 Jump Starting
5
-7 Towing Your Vehicle
5
-8 Engine Overheating
5
-9 Cooling System5
-18 Engine Fan Noise
5
-18 If a Tire Goes Flat
5
-19 Changing a Flat Tire
5
-30 Compact Spare Tire (If Equipped)
5
-31 If You're Stuck: In Sand, Mud, Ice or Snow

5-10
Cooling System
When you decide it's safe to lift the hood, here's
what you'll see:
A. Coolant Recovery Tank
B. Radiator Pressure Cap
C. Engine FanIf the coolant inside the coolant recovery tank is boiling,
don't do anything else until it cools down.
When the engine is cold, the coolant level should be at
least up to the ADD mark. If it isn't, you may have a
leak in the radiator hoses, heater hoses, radiator, water
pump or somewhere else in the cooling system.