1999 GMC C-SERIES coolant temperature

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3-5
OFF
Press this button to turn the air conditioning/heating
system off. Pressing OFF will erase the present mode of
operation from the system's memory. Outside air will
still come out of the heater outlet whenever the vehicle
is moving forward.
If the OFF button is pressed, you must press A/C,
MAX or one of the BLEND buttons to turn the system
back on.
Air Conditioning
When you first turn on your vehicle's air conditioning,
open the windows long enough to clear the vehicle of
hot air, then close them. Using the MAX button can also
help. See ªMAX Buttonº earlier in this section for
more information.
For normal cooling on hot days, use A/C with the
temperature selector toward C.
When you press the A/C button to turn the air
conditioner off, the system will operate in the vent
mode. When you turn the air conditioner back on, the
system will operate in the mode you last selected unless
the OFF button was pressed.If your air conditioner develops high system pressure, it
will automatically go into the MAX mode and REC will
light on your display. The A/C system will remain in the
MAX mode, even if you press the MAX button, until
system pressure returns to a normal level.
Heating
On cold days, use HEATER with the temperature
selector all the way toward H. When the inside of the
vehicle has reached a comfortable temperature, maintain
it by using the temperature selector bar.
If your vehicle is equipped with a diesel engine, and the
engine has been idling for a long time when it's cold
outside, your heater may blow out cool air. This is
normal. When you increase the engine speed under load,
your heater should blow out warmer air. If it doesn't,
your coolant level may be low. See ªEngine Coolantº in
the Index to check your coolant level.
While idling your diesel engine, you can use the MAX
button to recirculate the air in the cab to help maintain
interior heat. This will preserve engine coolant temperature
and cab heat when idling cannot be avoided.
Using the MAX button while driving is not recommended
because interior window fogging can result.
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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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6-22
Surge Tank Pressure Cap
(Diesel Engines)
The surge tank pressure cap
must be tightly installed
with the arrows on the cap
lined up with the top tube of
the coolant surge tank.
When you replace your surge tank pressure cap, an
ACDelco

cap is recommended.
NOTICE:
Your surge tank pressure cap is a 9 psi (62kPa)
pressure
-type cap for use with medium duty
cooling systems only. It must be tightly installed
to prevent coolant loss and possible engine
damage from overheating. Be sure the arrows on
the cap line up with the top tube of the coolant
surge tank.
Thermostat
Engine coolant temperature is controlled by one or more
thermostats in the engine cooling system. The
thermostat stops the flow of coolant through the radiator
until the coolant reaches a preset temperature.
When you replace your thermostat, an ACDelco


thermostat is recommended for gasoline engines.
Caterpillar
parts are recommended for diesel engines.
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6-23
Engine Coolant (Gasoline Engine)
The cooling system in your vehicle is filled with
DEX
-COOL
engine coolant. This coolant is designed
to remain in your vehicle for 5 years or 150,000 miles
(240 000 km), whichever occurs first, if you add only
DEX
-COOL
extended life coolant.
The following explains your cooling system and how to
add coolant when it is low. If you have a problem with
engine overheating, see ªEngine Overheatingº in
the Index.
A 50/50 mixture of clean, drinkable water and
DEX
-COOL
coolant will:

Give freezing protection down to
-34F (-37C).

Give boiling protection up to 252F (122C).

Protect against rust and corrosion.

Help keep the proper engine temperature.

Let the warning lights and gages work as
they should.
NOTICE:
When adding coolant, it is important that you
use only DEX
-COOL (silicate-free) coolant.
If coolant other than DEX-COOL is added to
the system, premature engine, heater core or
radiator corrosion may result. In addition, the
engine coolant will require change sooner
-- at
30,000 miles (50 000 km) or 24 months,
whichever occurs first. Damage caused by the
use of coolant other than DEX
-COOL is not
covered by your new vehicle warranty.
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7-28
Part C: Recommended Fluids
and Lubricants
NOTE: Fluids and lubricants identified below by
name, part number or specification may be obtained
from your dealer.
USAGE
FLUID/LUBRICANT
Engine Oil
(Gasoline
Engine)Engine Oil with the American
Petroleum Institute Certified For
Gasoline Engines ªStarburstº
symbol of the proper viscosity. To
determine the preferred viscosity
for your vehicle's engine, see
ªEngine Oilº in the Index.
Engine Oil
(Caterpillar
Diesel Engine)See the Caterpillar
Operation &
Maintenance Manual for Engine
Oil recommendations.
Engine Coolant
(GM Gasoline
Engine)50/50 mixture of clean, drinkable
water and use only GM
Goodwrench

DEX-COOL
or
Havoline
DEX-COOL

Coolant. See ªEngine Coolantº in
the Index.
USAGEFLUID/LUBRICANT
Engine Coolant
(Caterpillar
Diesel Engine)See the Caterpillar
Operation &
Maintenance Manual for Engine
Coolant recommendations.
Hydraulic Brake
SystemDelco Supreme 11
Brake Fluid
(GM Part No. 12377967 or
equivalent DOT
-3 Brake Fluid).
Windshield
Washer SolventGM Optikleen
Washer Solvent
(GM Part No. 1051515)
or equivalent.
Clutch Bearing
LubricantClutch Bearing Lubricant (GM
Part No. 12345777 or equivalent)
or NLGI #3 consistency.
Exhaust Brake
Ball Joint Cap
LubricantHigh-Temperature Grease (GM
Part No. 1051344 or equivalent) or
NLGI #3 consistency.
Spring Parking
Brake Hydraulic
PumpDEXRON
-III Automatic
Transmission Fluid.
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9-3
Cooling System
Capacity 6-74 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Diesel Engines 5-27, 6-25 . . . . . . . . . . . . . . . . . . . . . . . . . .
Gasoline Engines 5-20, 6-23 . . . . . . . . . . . . . . . . . . . . . . . .
Crankcase Capacity 6-74 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cruise Control 2-36 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Customer Assistance for Text Telephone Users 8-3 . . . . . . . . .
Customer Assistance Information 8-1 . . . . . . . . . . . . . . . . . . .
Customer Satisfaction Procedure 8-2 . . . . . . . . . . . . . . . . . . . .
Damage
Finish 6-65 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Sheet Metal 6-64 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Daytime Running Lamps 2-44 . . . . . . . . . . . . . . . . . . . . . . . . .
Daytime Running Lamps Indicator Light 2-67 . . . . . . . . . . . .
Defects, Reporting Safety 8-6, 8-7 . . . . . . . . . . . . . . . . . . . . .
Defensive Driving 4-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Defogging 3-6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Diesel Engine Exhaust Brake 2-16 . . . . . . . . . . . . . . . . . . . . . .
Diff Lock Indicator Light 2-63 . . . . . . . . . . . . . . . . . . . . . . . . .
Do Not Shift Light 2-57 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Dome Lamps 2-46 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Door
Latches Check 7
-27 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Locks 2-4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power Locks 2-4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Driver Position 1-11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Driving
City 4
-19 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Defensive 4-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Drunken 4
-3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Freeway 4-20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
In a Blizzard 4-26 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
In Rain and on Wet Roads 4-16 . . . . . . . . . . . . . . . . . . . . . .
Night 4-15 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
On Curves 4-10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
On Hill and Mountain Roads 4-22 . . . . . . . . . . . . . . . . . . . .
On Snow and Ice 4-24 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Through Water 4-18 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Winter 4-24 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Drunken Driving 4-3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Electrical Equipment, Adding 6-68 . . . . . . . . . . . . . . . . . . . .
Electrical System 6-68 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Engine
Air Cleaner Filter 6
-77 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Air Control 2-42 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Automatic Shutdown 2-11 . . . . . . . . . . . . . . . . . . . . . . . . . .
Coolant (Caterpillar
Diesel Engine) 6-27 . . . . . . . . . . . . .
Coolant (Gasoline Engine) 6-23 . . . . . . . . . . . . . . . . . . . . . .
Coolant Heater 2-15 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Coolant Level Check 7-23 . . . . . . . . . . . . . . . . . . . . . . . . . .
Coolant Temperature Gage 2-62 . . . . . . . . . . . . . . . . . . . . .
Cooling System Capacity 6-74 . . . . . . . . . . . . . . . . . . . . . . .
Crankcase Capacity 6-74 . . . . . . . . . . . . . . . . . . . . . . . . . . .
Diesel,Warm-Up 2-11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Exhaust 2-29, 2-30, 4-27 . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fan Breakage 6-3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fan Noise 5-33 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fast Idle System 2-12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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9-5
Gages
Air Pressure 2-69 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Engine Coolant Temperature 2-61 . . . . . . . . . . . . . . . . . . . .
Engine Oil Pressure 2-65 . . . . . . . . . . . . . . . . . . . . . . . . . . .
Filterminder 2-70 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuel 2-68 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Hourmeter 2-70 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Oil Pressure 2-65 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Speedometer 2-53 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Tachometer 2-54 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Transmission Temperature 2-69 . . . . . . . . . . . . . . . . . . . . . .
Voltmeter 2-56 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Guide en Fran†ais ii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Hazard Warning Flasher Switch 5-3 . . . . . . . . . . . . . . . . . . .
Hazard Warning Flashers 5-2 . . . . . . . . . . . . . . . . . . . . . . . . . .
Head Restraints 1-3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Headlamps 2-43 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
High/Low Beam Changer 2-34 . . . . . . . . . . . . . . . . . . . . . .
Wiring 6-68 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Heating 3-5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Highway Hypnosis 4-21 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Hill and Mountain Roads 4-22 . . . . . . . . . . . . . . . . . . . . . . . . .
Hood
Access Panels 6
-10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Checking Things Under 6-9 . . . . . . . . . . . . . . . . . . . . . . . . .
Latches Check 7-27 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Horn 2-31 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hourmeter Gage 2
-70 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Hydraulic Brake Warning Light 2-58 . . . . . . . . . . . . . . . . . . . .
Hydroplaning 4-18 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ignition Positions 2-6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Inflation, Tire 6-49 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Inspections
Engine Cover Check 7
-27 . . . . . . . . . . . . . . . . . . . . . . . . . .
Underbody 7-27 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Instrument Panel 2-50 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Circuit Breaker Block 6-69 . . . . . . . . . . . . . . . . . . . . . . . . .
Cleaning 6-61 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cluster 2-52 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Intake Heater Indicator Light 2-63 . . . . . . . . . . . . . . . . . . . . . .
Inter-Axle Differential Lock Control 2-40 . . . . . . . . . . . . . . . .
Jump Starting 5-5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Keys 2-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Labels
Certification/Tire 4-28, 6-67 . . . . . . . . . . . . . . . . . . . . . . . .
Service Parts Identification 6-67 . . . . . . . . . . . . . . . . . . . . .
Vehicle Identification Number 6-67 . . . . . . . . . . . . . . . . . . .
Lamp and Bulb Data 6-74 . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Lamp Check 7-26 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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