2012 GMC SIERRA 1500 cooling

Black plate (19,1)GMC Sierra Owner Manual - 2012 - CRC - 11/15/11
Vehicle Care 10-19
{WARNING
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 fire, and you
could be burned. Get any leak
fixed before you drive the vehicle.
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 50 000 km (30,000 mi)
or 24 months, whichever occurs
first. Any repairs would not
be covered by the vehicle
warranty. Always use DEX-COOL
(silicate-free) coolant in 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 on
page 10‑22.
What to Use
{WARNING
Adding only plain water or some
other liquid to the cooling system
can be dangerous. Plain water
and other liquids, can boil before
the proper coolant mixture will.
The coolant warning system is set
for the proper coolant mixture.
With plain water or the wrong
(Continued)
WARNING (Continued)
mixture, the engine could get too
hot but you would not get the
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.
Use a 50/50 mixture of clean,
drinkable water and DEX-COOL
coolant. If using this mixture,
nothing else needs to be added.
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

Black plate (20,1)GMC Sierra Owner Manual - 2012 - CRC - 11/15/11
10-20 Vehicle Care
.Will not damage aluminum parts
.Helps keep the proper engine
temperature
Notice: If an improper coolant
mixture is used, the engine could
overheat and be badly damaged.
The repair cost would not be
covered by the vehicle warranty.
Too much water in the mixture
can freeze and crack the engine,
radiator, heater core, and other
parts.
Notice: If extra inhibitors and/or
additives are used in the vehicle
cooling system, the vehicle
could be damaged. Use only the
proper mixture of the engine
coolant listed in this manual
for the cooling system. See
Recommended Fluids and
Lubricants on page 11‑12 for
more information. Never dispose of engine coolant
by putting it in the trash, pouring it
on the ground, or into sewers,
streams, or bodies of water.
Have the coolant changed by an
authorized service center, familiar
with legal requirements regarding
used coolant disposal. This will help
protect the environment and your
health.
Checking Coolant
The coolant surge tank is located in
the engine compartment on the
passenger side of the vehicle. See
Engine Compartment Overview on
page 10‑6
for more information on
location.
The vehicle must be on a level
surface when checking the coolant
level.
Check to see if coolant is visible in
the coolant surge tank. If the coolant
inside the coolant surge tank is
boiling, do not do anything else until it cools down. 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 is cool before this
is done.
The coolant level should be at or
above the FULL COLD mark. If it is
not, there may be a leak in the
cooling system.

Black plate (21,1)GMC Sierra Owner Manual - 2012 - CRC - 11/15/11
Vehicle Care 10-21
How to Add Coolant to the
Coolant Surge Tank for
Gasoline Engines
If the vehicle has a diesel engine,
see“Cooling System” in the
Duramax Diesel Supplement for
the proper coolant fill procedure.
{WARNING
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.
Notice: This vehicle has a
specific coolant fill procedure.
Failure to follow this procedure
could cause the engine to
overheat and be severely
damaged.
{WARNING
An electric engine cooling fan
under the hood 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
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. If no coolant is visible in the surge
tank, add coolant as follows:
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.

Black plate (22,1)GMC Sierra Owner Manual - 2012 - CRC - 11/15/11
10-22 Vehicle Care
3. Fill the coolant surge tank withthe 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. Be sure the pressure cap is
hand-tight and fully seated.
6. Verify coolant level after the engine is shut off and the
coolant is cold. If necessary,
repeat coolant fill procedure
Steps 1 through 6.
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.
Engine Overheating
If the vehicle has the Duramax®
Diesel engine, see the Duramax
Diesel Supplement for more
information.
The vehicle has several indicators
to warn of engine overheating. There is a coolant temperature
gauge on the vehicle's instrument
panel. See
Engine Coolant
Temperature Gauge on page 5‑16.
In addition, there are ENGINE
OVERHEATED STOP ENGINE,
ENGINE OVERHEATED IDLE
ENGINE, and ENGINE POWER IS
REDUCED messages in the Driver
Information Center (DIC) on the
instrument panel. See Engine
Cooling System Messages on
page 5‑41 andEngine Power
Messages on page 5‑42.
If the decision is made not to lift the
hood when this warning appears,
get service help right away. See
Roadside Assistance Program (U.S.
and Canada) on page 13‑7 or
Roadside Assistance Program
(Mexico) on page 13‑9.
If the decision is made to lift the
hood, make sure the vehicle is
parked on a level surface.

Black plate (23,1)GMC Sierra Owner Manual - 2012 - CRC - 11/15/11
Vehicle Care 10-23
Then check to see if the engine
cooling fans are running. If the
engine is overheating, both fans
should be running. If they are not,
do not continue to run the engine
and have the vehicle serviced.
Notice:Engine damage from
running your engine without
coolant is not covered by the
vehicle warranty. See Overheated
Engine Protection Operating
Mode for information on driving
to a safe place in an emergency.
Notice: If the engine catches fire
while driving with no coolant, the
vehicle can be badly damaged.
The costly repairs would not be
covered by the vehicle warranty.
See Overheated Engine
Protection Operating Mode on
page 10‑24 for information on
driving to a safe place in an
emergency.If Steam is Coming from the
Engine Compartment
{WARNING
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 fire. You
or others could be badly burned.
Stop the engine if it overheats,
and get out of the vehicle until the
engine is cool.
(Continued)
WARNING (Continued)
SeeOverheated Engine
Protection Operating Mode on
page 10‑24 for information on
driving to a safe place in an
emergency.
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.
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

Black plate (24,1)GMC Sierra Owner Manual - 2012 - CRC - 11/15/11
10-24 Vehicle Care
.Idles for long periods in traffic
.Tows a trailer; seeTrailer Towing
on page 9‑78.
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. If stopped in a traffic jam, apply the brake, shift to N (Neutral);
otherwise, shift to the highest
gear while driving —D (Drive)
or 3 (Third).
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.
If the warning continues, pull
over, stop, and park the vehicle
right away.
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. Also, see
“Overheated Engine Protection
Operating Mode”
later in this
section.
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 km (mi) 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. See
Engine Oil on page 10‑7.
Engine Fan
If the 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 fan is spinning slower and the
clutch is not fully engaged. This
improves fuel economy and reduces
fan noise. Under heavy vehicle

Black plate (25,1)GMC Sierra Owner Manual - 2012 - CRC - 11/15/11
Vehicle Care 10-25
loading, trailer towing, and/or high
outside temperatures, the fan speed
increases as the clutch more fully
engages, so an increase in fan
noise may be heard. 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.
This fan noise may also be heard
when starting the engine. It will go
away as the fan clutch partially
disengages.
If the vehicle has electric cooling
fans, the fans may be heard
spinning at low speed during most
everyday driving. The fans may
turn off if no cooling is required.
Under heavy vehicle loading, trailer
towing, high outside temperatures,
or operation of the air conditioning
system, the fans may change to
high speed and an increase in fan
noise may be heard. This is normal
and indicates that the coolingsystem is functioning properly. The
fans will change to low speed when
additional cooling is no longer
required.
Power Steering Fluid
See
Engine Compartment Overview
on page 10‑6 for reservoir location.
When to Check Power Steering
Fluid
It is not necessary to regularly
check power steering fluid unless
there is a leak suspected in the
system or an unusual noise is
heard. A fluid loss in this system
could indicate a problem. Have the
system inspected and repaired.
How to Check Power Steering
Fluid
Notice:Extremely small amounts
of contamination can cause
steering system damage and
cause it to not work properly. Do
not allow contaminants to contact
the fluid side of the reservoir cap/
dipstick or to enter the reservoir.
To check the power steering fluid:
1. Turn the key off and let the engine compartment cool down.
2. Wipe the cap and the top of the reservoir clean.
3. Unscrew the cap and wipe the dipstick with a clean rag.
4. Replace the cap and completely tighten it.
5. Remove the cap again and look at the fluid level on the dipstick.
The level should be at the FULL
COLD mark. If necessary, add only
enough fluid to bring the level up to
the mark.

Black plate (47,1)GMC Sierra Owner Manual - 2012 - CRC - 11/15/11
Vehicle Care 10-47
FusesUsage
51 Heated Mirrors
52 SEO B1 Upfitter Usage
(Battery)
53 Accessory Power Outlet
54 SEO Upfitter Usage
55 Climate Controls (Ignition)
56 Engine Control Module,
Secondary Fuel Pump
(Ignition)
J-Case Fuses Usage
57 Cooling Fan 1
58 Not Used
59 Heavy Duty Antilock
Brake System
60 Cooling Fan 2
61 Antilock Brake
System 1 J-Case
Fuses Usage
62 Starter
63 Stud 2 (Trailer Brakes)
64 Left Bussed Electrical
Center 1
65 Not Used
66 Not Used
67 Transfer Case
68 Stud 1 (Trailer
Connector
Battery Power)
(Optional - 40A Fuse
Required)
69 Mid-Bussed Electrical
Center 1
70 Climate Control Blower
71 Not Used
72 Left Bussed Electrical
Center 2 Relays
Usage
FAN HI Cooling Fan High
Speed
FAN LO Cooling Fan Low
Speed
FAN CNTRL Cooling Fan
Control
HDLP
LO/HID Low-Beam
Headlamp
FOG LAMP Front Fog Lamps
A/C
CMPRSR Air Conditioning
Compressor
STRTR Starter
PWR/TRN Powertrain
FUEL PMP Fuel Pump
PRK LAMP Parking Lamps
REAR
DEFOG Rear Defogger
RUN/CRNK Switched Power