2008 CHEVROLET TAHOE engine overheat

Adding Coolant
If more coolant is needed, add the proper DEX-COOL®
coolant mixture at the surge tank, but only when the
engine is cool.
{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 replacing the pressure cap, make sure it is
hand-tight and fully seated.
Coolant Surge Tank Pressure Cap
If your vehicle is a Two-mode Hybrid, see the Two-mode
Hybrid manual for more information.
Notice:If the pressure cap is not tightly installed,
coolant loss and possible engine damage may
occur. Be sure the cap is properly and tightly
secured.
The coolant surge tank pressure cap must be fully
installed on the coolant surge tank. SeeEngine
Compartment Overview on page 5-16for more
information on location.
Engine Overheating
There is a coolant temperature gage on your vehicle’s
instrument panel. SeeEngine Coolant Temperature
Gage on page 3-43.
In addition, ENGINE OVERHEATED STOP ENGINE,
ENGINE OVERHEATED IDLE ENGINE, and a ENGINE
POWER IS REDUCED message comes on in the Driver
Information Center (DIC) on the instrument panel.
SeeDIC Warnings and Messages on page 3-59.
5-34

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. 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 the vehicles engine
is overheated, the liquids in it can catch re.
You or others could be badly burned. Stop
your engine if it overheats, and get out of
the vehicle until the engine is cool.
SeeOverheated Engine Protection Operating
Mode on page 5-36for information on driving
to a safe place in an emergency.Notice:If the engine catches re while driving with
no coolant, the vehicle can be badly damaged.
The costly repairs would not be covered by
the vehicle warranty. SeeOverheated Engine
Protection Operating Mode on page 5-36for
information on driving to a safe place in an
emergency.
If No Steam Is Coming From Your
Engine
The ENGINE OVERHEATED STOP ENGINE or the
ENGINE OVERHEATED IDLE ENGINE message, along
with a low coolant condition, can indicate a serious
problem.
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.
Tow a trailer. SeeTowing a Trailer on page 4-49.
5-35

If you get the ENGINE OVERHEATED STOP ENGINE
or the ENGINE OVERHEATED IDLE ENGINE message
with no sign of steam, try this for a minute or so:
1. If the vehicle has an air conditioner and it is on,
turn it off.
2. Turn on the heater to the highest temperature and
at the highest fan speed and open the windows as
necessary.
3. In heavy traffic, let the engine idle in N (Neutral)
while stopped. If it is safe to do so, pull off the
road, shift to P (Park) or N (Neutral) and let
the engine idle.
If you no longer have the overheat warning, you can
drive. Just to be safe, drive slower for about 10 minutes.
If the warning does not come back on, you can drive
normally.
If the warning continues, pull over, stop, and park your
vehicle immediately.
If there is still no sign of steam and your vehicle has an
engine-driven cooling fan, push down the accelerator
until the engine speed is about twice as fast as normal
idle speed for at least ve minutes while parked.
If there is still no sign of steam and your vehicle has an
electric cooling fan, idle the engine for ve minutes
while parked.If you still have the warning, turn off the engine and get
everyone out of the vehicle until it cools down. Also,
see “Overheated Engine Protection Operating Mode”
later in this section.
You might decide not to lift the hood but to get service
help right away.
Overheated Engine Protection
Operating Mode
If an overheated engine condition exists and the
ENGINE POWER IS REDUCED message is displayed,
an overheat protection mode which alternates ring
groups of cylinders helps prevent engine damage.
In this mode, you will notice a loss in power and engine
performance. This operating mode allows your vehicle
to be driven to a safe place in an emergency. Driving
extended miles (km) and/or towing a trailer in the
overheat protection mode should be avoided.
Notice:After driving in the overheated engine
protection operating mode, to avoid engine damage,
allow the engine to cool before attempting any
repair. The engine oil will be severely degraded.
Repair the cause of coolant loss, change the oil
and reset the oil life system. SeeEngine Oil
on page 5-17.
5-36

Cooling System
If your vehicle is a Two-mode Hybrid, see the Two-mode
Hybrid manual for more information.
When you decide it is safe to lift the hood, here is what
you will see:
A. Coolant Surge Tank
B. Coolant Surge Tank Pressure Cap
C. Engine Cooling Fan(s){CAUTION:
An electric fan under the hood can start up
and injure you even when the engine is not
running. Keep hands, clothing, and tools away
from any underhood electric fan.
If the coolant inside the coolant surge tank is boiling,
do not do anything else until it cools down. If possible,
the vehicle should be parked on a level surface.
Check the coolant level after the system cools down.
Some amount of coolant may be lost due to overheating.
5.3L Engine (4.8L, 6.0L and 6.2L Similar)
5-37

The coolant level should be at or above 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.
Notice:Engine damage from running your engine
without coolant is not covered by your warranty.
SeeOverheated Engine Protection Operating Mode
on page 5-36for information on driving to a safe
place in an emergency.
Notice:Using coolant other than DEX-COOL
®can
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 vehicle warranty.
Always use DEX-COOL
®(silicate-free) coolant
in the vehicle.
5-38

How to Add Coolant to the Coolant
Surge Tank
If you have not found a problem yet, check to see if
coolant is visible in the surge tank. If coolant is visible
but the coolant level is not at or above the FULL COLD
mark, add a 50/50 mixture of clean, drinkable water
and DEX-COOL
®coolant at the coolant surge tank,
but be sure the cooling system, including the coolant
surge tank pressure cap, is cool before you do it.
SeeEngine Coolant on page 5-31for more information.
If no coolant is visible in the surge tank, add coolant
as follows:
{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 coolant
surge tank pressure cap — even a little — they
can come out at high speed. Never turn the
cap when the cooling system, including the
coolant surge tank pressure cap, is hot. Wait
for the cooling system and coolant surge tank
pressure cap to cool if you ever have to turn
the pressure cap.
{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.
5-39

Disc, MP3.............................................3-95, 3-99
Doing Your Own Service Work........................... 5-4
Dome Lamp Override......................................3-19
Dome Lamps .................................................3-18
Door
Delayed Locking..........................................2-11
Locks........................................................2-10
Power Door Locks.......................................2-10
Programmable Automatic Door Locks.............2-11
Rear Door Security Locks.............................2-11
Driver Information Center (DIC).........................3-51
DIC Operation and Displays..................3-51, 3-56
DIC Vehicle Customization............................3-67
DIC Warnings and Messages........................3-59
Driving
At Night.....................................................4-26
Before a Long Trip......................................4-28
Defensive..................................................... 4-2
Drunken....................................................... 4-2
Highway Hypnosis.......................................4-28
Hill and Mountain Roads..............................4-29
In Rain and on Wet Roads...........................4-26
Off-Road ....................................................4-13
Recovery Hooks..........................................4-34
Rocking Your Vehicle to Get it Out.................4-34
Winter........................................................4-30
Dual Automatic Climate Control System.............3-24
DVD
Rear Seat Entertainment System..................3-105E
EDR .............................................................7-17
Electrical System
Add-On Equipment.....................................5-119
Center Instrument Panel Fuse Block.............5-121
Fuses and Circuit Breakers.........................5-119
Instrument Panel Fuse Block.......................5-120
Power Windows and Other Power Options....5-119
Underhood Fuse Block...............................5-122
Windshield Wiper Fuses.............................5-119
Electronic Immobilizer
PASS-Key
®III+...........................................2-22
Electronic Immobilizer Operation
PASS-Key
®III+...........................................2-23
Engine
Air Cleaner/Filter.........................................5-22
Check and Service Engine Soon Light............3-44
Coolant......................................................5-31
Coolant Heater............................................2-28
Coolant Temperature Gage...........................3-43
Drive Belt Routing.......................................6-16
Engine Compartment Overview......................5-16
Exhaust.....................................................2-46
Fan Noise..................................................5-41
Oil .............................................................5-17
Oil Life System...........................................5-20
Overheated Protection Operating Mode...........5-36
Overheating................................................5-34
Starting......................................................2-26
4

Older Children, Restraints................................1-50
Online Owner Center........................................ 7-5
OnStar, Privacy..............................................7-18
OnStar
®System, see OnStar®Manual...............2-59
Operation, Universal Home Remote System........2-63
Other Warning Devices...................................... 3-6
Outlet Adjustment............................................3-30
Outlets
Accessory Power.........................................3-20
Outside
Automatic Dimming Mirror.............................2-55
Convex Mirror.............................................2-55
Heated Mirrors............................................2-56
Manual Mirrors............................................2-52
Power Foldaway Mirrors...............................2-54
Power Mirrors.............................................2-53
Towing Mirrors............................................2-52
Overheated Engine Protection Operating Mode.....5-36
Owner Checks and Services.............................6-10
Owners, Canadian.............................................. iii
P
Paint, Damage..............................................5-116
Park
Shifting Into................................................2-43
Shifting Out of............................................2-45Park Aid........................................................2-56
Park Brake....................................................2-42
Park Tilt Mirrors..............................................2-55
Parking
Assist........................................................2-56
Over Things That Burn.................................2-45
Passenger Airbag Status Indicator.....................3-38
Passenger Sensing System..............................1-85
Passing.........................................................4-11
PASS-KEY
®III+ Electronic Immobilizer...............2-22
PASS-Key®III+ Electronic Immobilizer Operation . . . 2-23
Perchlorate Materials Requirements, California...... 5-4
Power
Door Locks.................................................2-10
Electrical System.......................................5-119
Liftgate......................................................2-14
Lumbar Controls........................................... 1-4
Retained Accessory (RAP)............................2-26
Running Boards..........................................2-17
Seat............................................................ 1-3
Steering Fluid.............................................5-42
Windows....................................................2-19
Privacy..........................................................7-17
Event Data Recorders..................................7-17
Navigation System.......................................7-18
OnStar.......................................................7-18
Radio Frequency Identication.......................7-18
Programmable Automatic Door Locks.................2-11
9