2008 GMC ENVOY cooling

The coolant level should
be at least up to the FULL
COLD mark. If it is not,
you may have a leak at the
pressure cap or in the
radiator hoses, heater
hoses, radiator, water
pump, or somewhere else
in the cooling system.
{CAUTION:
Heater and radiator hoses, and other engine
parts, can be very hot. Do not touch them. If
you do, you can be burned.
Do not run the engine if there is a leak. If you
run the engine, it could lose all coolant. That
could cause an engine re, and you could be
burned. Get any leak xed before you drive the
vehicle.If there seems to be no leak, start the engine again.
The engine cooling fan speed should increase when
idle speed is doubled by pushing the accelerator pedal
down. If it does not, your vehicle needs service.
Turn off the engine.
Notice:Engine damage from running the engine
without coolant is not covered by the warranty.
Notice:Using coolant other than DEX-COOL
®may
cause premature engine, heater core, or radiator
corrosion. In addition, the engine coolant could
require changing sooner, at 30,000 miles (50 000 km)
or 24 months, whichever occurs rst. Any repairs
would not be covered by the warranty. Always
use DEX-COOL
®(silicate-free) coolant in the vehicle.
5-31

How to Add Coolant to the Coolant
Recovery Tank
If you have not found a problem yet, but the coolant
level is not at the FULL COLD mark, add a
50/50 mixture of clean, drinkable water and DEX-COOL
®
engine coolant at the coolant recovery tank. See
Engine Coolant on page 5-26for more information.
{CAUTION:
Adding only plain water to the cooling system
can be dangerous. Plain water, or some other
liquid such as alcohol, can boil before the
proper coolant mixture will. The vehicle’s
coolant warning system is set for the proper
coolant mixture. With plain water or the wrong
mixture, the engine could get too hot but you
would not get the overheat warning. The
engine could catch re and you or others
could be burned. Use a 50/50 mixture of clean,
drinkable water and DEX-COOL
®coolant.Notice:In cold weather, water can freeze and crack
the engine, radiator, heater core and other parts.
Use the recommended coolant and the proper
coolant mixture.
{CAUTION:
You can be burned if you spill coolant on hot
engine parts. Coolant contains ethylene glycol
and it will burn if the engine parts are hot
enough. Do not spill coolant on a hot engine.
When the coolant in the coolant recovery tank is at the
FULL COLD mark, start your vehicle.
If the overheat warning continues, there is one more
thing you can try. You can add the proper coolant
mixture directly to the radiator, but be sure the cooling
system is cool before you do it.
5-32

{CAUTION:
Steam and scalding liquids from a hot cooling
system can blow out and burn you badly. They
are under pressure, and if you turn the radiator
pressure cap — even a little — they can come
out at high speed. Never turn the cap when the
cooling system, including the radiator pressure
cap, is hot. Wait for the cooling system and
radiator pressure cap to cool if you ever have
to turn the pressure cap.
How to Add Coolant to the Radiator
1. You can remove the radiator pressure cap when
the cooling system, including the radiator pressure
cap and upper radiator hose, is no longer hot.
Turn the pressure cap slowly counterclockwise about
one full turn. If you hear a hiss, wait for that to stop.
A hiss means there is still some pressure left.
2. Then keep turning the pressure cap. Remove the
pressure cap.
5-33

6. Start the engine and let it run until you can feel the
upper radiator hose getting hot. Watch out for the
engine cooling fan.
7. By this time, the coolant level inside the radiator
ller neck may be lower. If the level is lower, add
more of the proper DEX-COOL
®coolant mixture
through the ller neck until the level reaches the
base of the ller neck.
8. Then replace the pressure cap. At any time during
this procedure if coolant begins to ow out of the
ller neck, reinstall the pressure cap. Be sure
the pressure cap is hand-tight and fully seated.
Engine Fan Noise
Your vehicle has a clutched engine cooling fan. When
the clutch is engaged, the fan spins faster to provide
more air to cool the engine. In most everyday driving
conditions the clutch is not engaged. This improves fuel
economy and reduces fan noise. Under heavy vehicle
loading, trailer towing, and/or high outside temperatures,
the fan speed increases when the clutch engages so
you may hear an increase in fan noise. This is normal
and should not be mistaken as the transmission slipping
or making extra shifts. It is merely the cooling system
functioning properly. The fan will slow down when
additional cooling is not required and the clutch
disengages.
You may also hear this fan noise when you start the
engine. It will go away as the fan clutch disengages.
5-35

Each new wheel should have the same load-carrying
capacity, diameter, width, offset, and be mounted
the same way as the one it replaces.
If you need to replace any of your wheels, wheel bolts,
wheel nuts, or Tire Pressure Monitor System (TPMS)
sensors, replace them only with new GM original
equipment parts. This way, you will be sure to have the
right wheel, wheel bolts, wheel nuts, and TPMS sensors
for your vehicle.
{CAUTION:
Using the wrong replacement wheels, wheel
bolts, or wheel nuts on your vehicle can be
dangerous. It could affect the braking and
handling of your vehicle, make your tires lose
air and make you lose control. You could have
a collision in which you or others could be
injured. Always use the correct wheel, wheel
bolts, and wheel nuts for replacement.Notice:The wrong wheel can also cause problems
with bearing life, brake cooling, speedometer or
odometer calibration, headlamp aim, bumper height,
vehicle ground clearance, and tire or tire chain
clearance to the body and chassis.
SeeChanging a Flat Tire on page 5-82for more
information.
Used Replacement Wheels
{CAUTION:
Putting a used wheel on your vehicle is
dangerous. You cannot know how it has been
used or how far it has been driven. It could fail
suddenly and cause a crash. If you have to
replace a wheel, use a new GM original
equipment wheel.
5-79

Fuses Usage
5 Driver Side High-Beam Headlamp
6 Driver Side Low-Beam Headlamp
7 Windshield Wiper
8 Active Transfer Case
9 Windshield Washer
10 Powertrain Control Module B
11 Fog Lamps
12 Stoplamp
13 Cigarette Lighter
15 Electric Adjustable Pedals
16 Truck Body Controller, Ignition 1
17 Crank
18 Airbag
19 Trailer Electric Brake
20 Cooling Fan
21 Horn
22 Ignition EFuses Usage
23 Electronic Throttle Control
24Instrument Panel Cluster, Driver
Information Center
25Automatic Shift Lock Control
System
26Transmission Control Module
Canister
27 Backup
28 Powertrain Control Module 1
29 Oxygen Sensor
30 Air Conditioning
31 Truck Body Controller 1
32 Trailer
33 Antilock Brakes (ABS)
34 Ignition A
35 Blower Motor
36 Blower
50 Passenger Side Trailer Turn
5-112

Fuses Usage
51 Driver Side Trailer Turn
52 Hazard Flashers
53 Headlamp Driver Module
54Air Injection Reactor (AIR)
Solenoid
56 Air Injection Reactor (AIR) Pump
58Vehicle Stability Enhancement
System (StabiliTrak
®)
59 Regulated Voltage Control
Relays Usage
37 Headlamp Wiper
38 Rear Window Wiper/Washer
39 Fog Lamps
40 Horn
Relays Usage
41 Fuel Pump
42 Windshield Washer
43 High-Beam Headlamp
44 Air Conditioning
45 Cooling Fan
46 Headlamp Driver Module
47 Starter
49 Electric Adjustable Pedal
55 Air Injection Reactor (AIR) Solenoid
57 Powertrain
Miscellaneous Usage
48 Instrument Panel Battery
5-113

Fuses Usage
5 Driver Side High-Beam Headlamp
6 Driver Side Low-Beam Headlamp
7 Windshield Wiper
8 Active Transfer Case
9 Windshield Washer
10 Powertrain Control Module B
11 Fog Lamps
12 Stoplamp
13 Cigarette Lighter
14 Ignition Coils
15Transmission Control Module
(TCM) Canister Vent
16 Truck Body Controller, Ignition 1
17 Crank
18 Airbag
19 Trailer Electric Brake
20 Cooling Fan
21 Horn
22 Ignition E
23 Electronic Throttle ControlFuses Usage
24Instrument Panel Cluster, Driver
Information Center
25Automatic Shift Lock Control
System
26 Engine 1
27 Backup
28 Powertrain Control Module 1
29 Powertrain Control Module
30 Air Conditioning
31 Injector Bank A
32 Trailer
33 Antilock Brakes (ABS)
34 Ignition A
35 Blower Motor
36 Ignition B
50 Passenger Side Trailer Turn
51 Driver Side Trailer Turn
52 Hazard Flashers
53 Transmission
54 Oxygen Sensor Bank B
55 Oxygen Sensor Bank A
5-115