2018 GMC SIERRA engine overheat

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
360 Vehicle Care
6.0L V8 Engine
1. Coolant Surge Tank
2. Coolant Surge TankPressure Cap
3. Engine Belt-Driven Cooling Fan (Out of View)
{Warning
An underhood electric fan can
start up even when the engine is
not running and can cause injury.
Keep hands, clothing, and tools
away from any underhood
electric fan.
{Warning
Do not touch heater or radiator
hoses, or other engine parts.
They can be very hot and can
burn you. Do not run the engine if
there is a leak; all coolant could
leak out. That could cause an
engine fire and can burn you. Fix
any leak before driving the
vehicle.
Engine Coolant
The cooling system in the vehicle is
filled with DEX-COOL engine
coolant. This coolant is designed to
remain in the vehicle for 5 years or
240 000 km (150,000 mi), whichever
occurs first.
The following explains the cooling
system and how to check and add
coolant when it is low. If there is a
problem with engine overheating,
see Engine Overheating 0363.
What to Use
{Warning
Plain water, or other liquids such
as alcohol, can boil before the
proper coolant mixture will. With
plain water or the wrong mixture,
the engine could get too hot but
there would not be an overheat
warning. The engine could catch
fire and you or others could be
burned.
Use a 50/50 mixture of clean,
drinkable water and DEX-COOL
coolant. This mixture:
. Gives freezing protection down
to−37 °C (−34 °F), outside
temperature.
. Gives boiling protection up to
129 °C (265 °F), engine
temperature.
. Protects against rust and
corrosion.
. Will not damage aluminum parts.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
362 Vehicle Care
{Warning
Plain water, or other liquids such
as alcohol, can boil before the
proper coolant mixture will. With
plain water or the wrong mixture,
the engine could get too hot but
there would not be an overheat
warning. The engine could catch
fire and you or others could be
burned.
{Warning
Steam and scalding liquids from a
hot cooling system are under
pressure. Turning the pressure
cap, even a little, can cause them
to come out at high speed and
you could be burned. Never turn
the cap when the cooling system,
including the pressure cap, is hot.
Wait for the cooling system and
pressure cap to cool.
Warning
Failure to follow the specific
coolant fill procedure could cause
the engine to overheat and could
cause system damage. If coolant
is not visible in the surge tank,
contact your dealer.
If no coolant is visible in the surge
tank, add coolant.
Light-Duty
Coolant Surge
Tank
Pressure CapHeavy-Duty
Coolant Surge
Tank
Pressure Cap
1. Remove the coolant surge tank pressure cap when the cooling
system, including the coolant
surge tank pressure cap and
upper radiator hose, is no
longer hot. Turn the pressure cap slowly
counterclockwise about one full
turn. If a hiss is heard, wait for
that to stop. A hiss means
there is still some pressure left.
2. Keep turning the pressure cap slowly, and remove it.
3. Fill the coolant surge tank with the proper mixture to the full
cold mark.
4. With the coolant surge tank pressure cap off, start the
engine and let it run until the
engine coolant temperature
gauge indicates approximately
90 °C (195 °F).
By this time, the coolant level
inside the coolant surge tank
may be lower. If the level is
lower, add more of the proper
mixture to the coolant surge
tank until the level reaches the
full cold mark.
5. Replace the pressure cap tightly.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
Vehicle Care 363
6. Verify coolant level after theengine is shut off and the
coolant is cold. If necessary,
repeat coolant fill procedure
Steps 1–6.
Caution
If the pressure cap is not tightly
installed, coolant loss and engine
damage may occur. Be sure the
cap is properly and tightly
secured.
Engine Overheating
If the vehicle has the Duramax
diesel engine, see the Duramax
diesel supplement.
Caution
Do not run the engine if there is a
leak in the engine cooling system.
This can cause a loss of all
coolant and can damage the
system and vehicle. Have any
leaks fixed right away. The vehicle has several indicators
to warn of engine overheating.
There is a coolant temperature
gauge in the vehicle's instrument
cluster. See
Engine Coolant
Temperature Gauge 0144.
In addition, there are ENGINE
OVERHEATED STOP ENGINE,
ENGINE OVERHEATED IDLE
ENGINE, and ENGINE POWER IS
REDUCED messages in the Driver
Information Center (DIC).
If the decision is made not to lift the
hood when this warning appears,
get service help right away. See
Roadside Assistance Program
0 469.
If the decision is made to lift the
hood, make sure the vehicle is
parked on a level surface.
4.3L V6, 5.3L V8, and 6.2L
V8 Engines
Check to see if the engine cooling
fans are running. If the engine is
overheating, the fans should be running. If they are not, do not
continue to run the engine and have
the vehicle serviced.
If Steam is Coming from the
Engine Compartment
{Warning
Steam and scalding liquids from a
hot cooling system are under
pressure. Turning the pressure
cap, even a little, can cause them
to come out at high speed and
you could be burned. Never turn
the cap when the cooling system,
including the pressure cap, is hot.
Wait for the cooling system and
pressure cap to cool.
If No Steam is Coming from
the Engine Compartment
The ENGINE OVERHEATED STOP
ENGINE or the ENGINE
OVERHEATED IDLE ENGINE
message, along with a low coolant
condition, can indicate a serious
problem.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
364 Vehicle Care
If there is an engine overheat
warning, but no steam is seen or
heard, the problem may not be too
serious. Sometimes the engine can
get a little too hot when the vehicle:
.Climbs a long hill on a hot day.
. Stops after high-speed driving.
. Idles for long periods in traffic.
. Tows a trailer; see Trailer Towing
0 307.
If the ENGINE OVERHEATED
STOP ENGINE or the ENGINE
OVERHEATED IDLE ENGINE
message appears with no sign of
steam, try this for a minute or so: 1. Turn the air conditioning off.
2. Turn the heater on to the highest temperature and to the
highest fan speed. Open the
windows as necessary.
3. When it is safe to do so, pull off the road, shift to P (Park) or
N (Neutral) and let the
engine idle. If the temperature overheat gauge is
no longer in the overheat zone or an
overheat warning no longer
displays, the vehicle can be driven.
Continue to drive the vehicle slowly
for about 10 minutes. Keep a safe
vehicle distance from the vehicle in
front. If the warning does not come
back on, continue to drive normally
and have the cooling system
checked for proper fill and function.
If the warning continues, pull over,
stop, and park the vehicle
right away.
If there is still no sign of steam and
the vehicle is equipped with 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
five minutes while the vehicle is
parked. If the warning is still there,
turn off the engine and get everyone
out of the vehicle until it cools down.
If there is no sign of steam, idle the
engine for five minutes while
parked. If the warning is still
displayed, turn off the engine until it
cools down.Overheated Engine
Protection
Operating Mode
If an overheated engine condition
exists and the ENGINE POWER IS
REDUCED message displays, an
overheat protection mode which
alternates firing groups of cylinders
helps to prevent engine damage. In
this mode, a loss in power and
engine performance will be noticed.
This operating mode allows the
vehicle to be driven to a safe place
in an emergency. Driving extended
distances and/or towing a trailer in
the overheat protection mode
should be avoided.
Caution
After driving in the overheated
engine protection operating
mode, the engine oil will be
severely degraded. Any repairs
performed before the engine is
cool may cause engine damage.
Allow the engine to cool before
(Continued)

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
Vehicle Care 381
Headlamp Wiring
An electrical overload may cause
the lamps to go on and off, or in
some cases to remain off. Have the
headlamp wiring checked right away
if the lamps go on and off or
remain off.
Windshield Wipers
If the wiper motor overheats due to
heavy snow or ice, the windshield
wipers will stop until the motor cools
and will then restart.
Although the circuit is protected
from electrical overload, overload
due to heavy snow or ice may
cause wiper linkage damage.
Always clear ice and heavy snow
from the windshield before using the
windshield wipers.
If the overload is caused by an
electrical problem and not snow or
ice, be sure to get it fixed.
Fuses and Circuit
Breakers
The wiring circuits in the vehicle are
protected from short circuits by a
combination of fuses and circuit
breakers. This greatly reduces the
chance of damage caused by
electrical problems.
{Danger
Fuses and circuit breakers are
marked with their ampere rating.
Do not exceed the
specified amperage rating when
replacing fuses and circuit
breakers. Use of an oversized
fuse or circuit breaker can result
in a vehicle fire. You and others
could be seriously injured or
killed.
To check a fuse, look at the
silver-colored band inside the fuse.
If the band is broken or melted,
replace the fuse. Be sure to replace
a bad fuse with a new one of the
identical size and rating. Fuses of the same amperage can
be temporarily borrowed from
another fuse location, if a fuse goes
out. Replace the fuse as soon as
possible.
Engine Compartment
Fuse Block
If the vehicle has a diesel engine,
see the Duramax diesel
supplement.
The engine compartment fuse block
is in the engine compartment, on
the driver side of the vehicle.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
494 Index
D
Damage Repair, Collision . . . . . . . 472
Danger, Warning, and Caution . . . . 3
Data CollectionInfotainment System . . . . . . . . . . 478
OnStar . . . . . . . . . . . . . . . . . . . . . . . 478
Data Recorders, Event . . . . . . . . . 477
Daytime Running Lamps (DRL) . . . . . . . . . . . . . . . . . . 179
Defensive Driving . . . . . . . . . . . . . . . 236
Diagnostics
OnStar . . . . . . . . . . . . . . . . . . . . . . . 484
Distracted Driving . . . . . . . . . . . . . . . 235
Dome Lamps . . . . . . . . . . . . . . . . . . . 183
Door Ajar Light . . . . . . . . . . . . . . . . . . . . . 158
Locks . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Power Locks . . . . . . . . . . . . . . . . . . . . 41
Drive Belt Routing, Engine . . . . . . 464
Driver Assistance Systems . . . . . 288
Driver Information
Center (DIC) . . . . . . . . . . . . . 158, 160
Driving Assistance Systems . . . . . . . . . . 292
Characteristics and
Towing Tips . . . . . . . . . . . . . . . . . 303
Defensive . . . . . . . . . . . . . . . . . . . . . 236
Drunk . . . . . . . . . . . . . . . . . . . . . . . . . 236 Driving (cont'd)
For Better Fuel Economy . . . . . . . 33
Hill and Mountain Roads . . . . . . 245
If the Vehicle is Stuck . . . . . . . . . 247
Loss of Control . . . . . . . . . . . . . . . 238
Off-Road . . . . . . . . . . . . . . . . . . . . . 239
Off-Road Recovery . . . . . . . . . . . 238
Vehicle Load Limits . . . . . . . . . . . 248
Wet Roads . . . . . . . . . . . . . . . . . . . 244
Winter . . . . . . . . . . . . . . . . . . . . . . . . 245
Dual Automatic Climate Control System . . . . . . . . . . . . . . . . 228
E
E85 or FlexFuel . . . . . . . . . . . . . . . . 300
Electrical Equipment,Add-On . . . . . . . . . . . . . . . . . . . . . . . 336
Electrical System Engine Compartment Fuse
Block . . . . . . . . . . . . . . . . . . . . . . . . 381
Fuses and Circuit Breakers . . . 381
Instrument Panel Fuse Block . . . . . . . . . . . . . . . . . . . 385, 386
Overload . . . . . . . . . . . . . . . . . . . . . 380
Emergency OnStar . . . . . . . . . . . . . . . . . . . . . . . 480
Engine Air Cleaner/Filter . . . . . . . . . . . . . 358 Engine (cont'd)
Check Light (Malfunction
Indicator) . . . . . . . . . . . . . . . . . . . . 150
Compartment Overview . . . . . . . 345
Coolant Heater . . . . . . . . . . . . . . . 260
Coolant Temperature
Gauge . . . . . . . . . . . . . . . . . . . . . . 144
Coolant Temperature Warning Light . . . . . . . . . . . . . . . 155
Cooling System . . . . . . . . . . . . . . . 359
Drive Belt Routing . . . . . . . . . . . . 464
Exhaust . . . . . . . . . . . . . . . . . . . . . . 264
Fan . . . . . . . . . . . . . . . . . . . . . . . . . . . 365
Oil Life System . . . . . . . . . . . . . . . 353
Oil Pressure Gauge . . . . . . . . . . 143
Oil Pressure Light . . . . . . . . . . . . 156
Overheated Protection Operating Mode . . . . . . . . . . . . . 364
Overheating . . . . . . . . . . . . . . . . . . 363
Power Messages . . . . . . . . . . . . . 164
Running While Parked . . . . . . . . 265
Starting . . . . . . . . . . . . . . . . . . . . . . . 258
Entry Lighting . . . . . . . . . . . . . . . . . . . 184
Equipment, Towing . . . . . . . . . . . . . 325
Event Data Recorders . . . . . . . . . . 477
Exit Lighting . . . . . . . . . . . . . . . . . . . . 184
Extender, Seat Belt . . . . . . . . . . . . . . 75
Exterior Lamp Controls . . . . . . . . . 176

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
498 Index
Maintenance Schedule (cont'd)Recommended Fluids and
Lubricants . . . . . . . . . . . . . . . . . . . 456
Transfer Case . . . . . . . . . . . . . . . . 272
Malfunction Indicator Lamp . . . . . 150
Manual Mirrors . . . . . . . . . . . . . . . . . . 47
Manual Mode . . . . . . . . . . . . . . . . . . . 268
Manual Windows . . . . . . . . . . . . . . . . 52
Media Avoiding Untrusted Devices . . 195
Memory Features . . . . . . . . . . . . . . . . 13
Memory Seats . . . . . . . . . . . . . . . . . . . 62
Messages Engine Power . . . . . . . . . . . . . . . . 164
Vehicle . . . . . . . . . . . . . . . . . . . . . . . 164
Vehicle Speed . . . . . . . . . . . . . . . . 164
Mirrors Automatic Dimming . . . . . . . . . . . . . 50
Automatic Dimming
Rearview . . . . . . . . . . . . . . . . . . . . . . 52
Blind Spot . . . . . . . . . . . . . . . . . . . . . . 50
Convex . . . . . . . . . . . . . . . . . . . . . . . . . 47
Folding . . . . . . . . . . . . . . . . . . . . . . . . . 49
Heated . . . . . . . . . . . . . . . . . . . . . . . . . 50
Manual . . . . . . . . . . . . . . . . . . . . . . . . . 47
Manual Rearview . . . . . . . . . . . . . . . 52
Power . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Tilt in Reverse . . . . . . . . . . . . . . . . . . 51 Mirrors (cont'd)
Trailer Tow . . . . . . . . . . . . . . . . . . . . . . 48
Mirrors, Interior Rearview . . . . . . . . 51
Monitor System, Tire Pressure . . . . . . . . . . . . . . . . . . . . . . 399
Multi-band Antenna . . . . . . . . . . . . . 194
N
Navigation OnStar . . . . . . . . . . . . . . . . . . . . . . . 481
New Vehicle Break-In . . . . . . . . . . . 255
Noise Control System . . . . . . . . . . 373
O
Odometer . . . . . . . . . . . . . . . . . . . . . . . 142 Trip . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
Off-Road . . . . . . . . . . . . . . . . . . . . . . . 239 Driving . . . . . . . . . . . . . . . . . . . . . . . . 239
Recovery . . . . . . . . . . . . . . . . . . . . . 238
Oil
Engine . . . . . . . . . . . . . . . . . . . . . . . . 350
Engine Oil Life System . . . . . . . 353
Engine Oil Pressure Gauge . . . 143
Pressure Light . . . . . . . . . . . . . . . . 156
Older Children, Restraints . . . . . . . 92
Online Owner Center . . . . . . . . . . . 468
OnStar . . . . . . . . . . . . . . . . . . . . . . . . . 478
OnStar Additional Information . . . . . . . . . . . . . . . . . . . . 485 OnStar Connections . . . . . . . . . . . . 482
OnStar Diagnostics . . . . . . . . . . . . . 484
OnStar Emergency . . . . . . . . . . . . . 480
OnStar Navigation . . . . . . . . . . . . . . 481
OnStar Overview . . . . . . . . . . . . . . . 479
OnStar Security . . . . . . . . . . . . . . . . 481
Operating Mode
Overheated EngineProtection . . . . . . . . . . . . . . . . . . . 364
Operation Fog Lamps . . . . . . . . . . . . . . . . . . . 181
Ordering Service Publications . . . . . . . . . . 474
Outlets Power . . . . . . . . . . . . . . . . . . . . . . . . 133
Overheated Engine
Protection Operating Mode . . . . 364
Overheating, Engine . . . . . . . . . . . . 363
Overview . . . . . . . . . . . . . . . . . . . . . . . 188
P
Park Shifting Into . . . . . . . . . . . . . . . . . . . 262
Shifting Out of . . . . . . . . . . . . . . . . 263
Parking Brake . . . . . . . . . . . . . . . . . . . . . . . . . 281
Brake and P (Park)
Mechanism Check . . . . . . . . . . 375