2004 GMC YUKON engine overheat

If you decide you can go down a hill safely, then try to
keep your vehicle headed straight down, and use a
low gear. This way, engine drag can help your brakes
and they will not have to do all the work. Descend
slowly, keeping your vehicle under control at all times.
{CAUTION:
Heavy braking when going down a hill can
cause your brakes to overheat and fade. This
could cause loss of control and a serious
accident. Apply the brakes lightly when
descending a hill and use a low gear to keep
vehicle speed under control.
Q:Are there some things I should not do when
driving down a hill?
A:Yes! These are important because if you ignore
them you could lose control and have a serious
accident.
When driving downhill, avoid turns that take you
across the incline of the hill. A hill that is not too
steep to drive down may be too steep to drive
across. You could roll over if you do not drive
straight down.
Never go downhill with the transmission in
NEUTRAL (N). This is called “free-wheeling.” Your
brakes will have to do all the work and could
overheat and fade.
Q:Am I likely to stall when going downhill?
A:It is much more likely to happen going uphill. But if
it happens going downhill, here is what to do.
Stop your vehicle by applying the regular brakes.
Apply the parking brake.
Shift to PARK (P) and, while still braking, restart the
engine.
Shift back to a low gear, release the parking brake,
and drive straight down.
If the engine will not start, get out and get help.
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Then, shut the engine off and close the window almost
all the way to preserve the heat. Start the engine
again and repeat this only when you feel really
uncomfortable from the cold. But do it as little as
possible. Preserve the fuel as long as you can. To help
keep warm, you can get out of the vehicle and do
some fairly vigorous exercises every half hour or so until
help comes.
If You Are Stuck: In Sand, Mud, Ice
or Snow
In order to free your vehicle when it is stuck, you will
need to spin the wheels, but you do not want to
spin your wheels too fast. The method known as
“rocking” can help you get out when you are stuck, but
you must use caution.
{CAUTION:
If you let your tires spin at high speed, they
can explode, and you or others could be
injured. And, the transmission or other parts of
the vehicle can overheat. That could cause an
engine compartment re or other damage.
When you are stuck, spin the wheels as little
as possible. Do not spin the wheels above
35 mph (55 km/h) as shown on the
speedometer.
Notice:Spinning your wheels can destroy parts of
your vehicle as well as the tires. If you spin the
wheels too fast while shifting your transmission
back and forth, you can destroy your transmission.
For information about using tire chains on your
vehicle, seeTire Chains on page 5-82.
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Driving On Grades
Reduce speed and shift to a lower gearbeforeyou start
down a long or steep downgrade. If you don’t shift
down, you might have to use your brakes so much that
they would get hot and no longer work well.
You can tow in DRIVE (D). You may want to shift the
transmission to THIRD (3) or, if necessary, a lower gear
selection if the transmission shifts too often (e.g.,
under heavy loads and/or hilly conditions).
You may also want to activate the tow/haul mode if the
transmission shifts too often. See “Tow/Haul Mode”
earlier in this section for more information.
When towing at high altitude on steep uphill grades,
consider the following: Engine coolant will boil at a lower
temperature than at normal altitudes. If you turn your
engine off immediately after towing at high altitude on
steep uphill grades, your vehicle may show signs similar
to engine overheating. To avoid this, let the engine run
while parked (preferably on level ground) with the
automatic transmission in PARK (P) for a few minutes
before turning the engine off. If you do get the overheat
warning, seeEngine Overheating on page 5-29.
Parking on Hills
{CAUTION:
You really should not park your vehicle, with a
trailer attached, on a hill. If something goes
wrong, your rig could start to move. People
can be injured, and both your vehicle and the
trailer can be damaged.
But if you ever have to park your rig on a hill, here’s
how to do it:
1. Apply your regular brake, but don’t shift into
PARK (P) yet.
2. Have someone place chocks under the trailer
wheels.
3. When the wheel chocks are in place, release the
regular brakes until the chocks absorb the load.
4. Reapply the regular brakes. Then apply your
parking brake and shift into PARK (P).
4-73

Service............................................................5-3
Doing Your Own Service Work.........................5-3
Adding Equipment to the Outside of Your
Vehicle......................................................5-4
Fuel................................................................5-4
Gasoline Octane............................................5-4
Gasoline Specications....................................5-5
California Fuel...............................................5-5
Additives.......................................................5-6
Fuel E-85 (85% Ethanol).................................5-6
Fuels in Foreign Countries...............................5-8
Filling Your Tank............................................5-8
Filling a Portable Fuel Container.....................5-10
Checking Things Under the Hood....................5-10
Hood Release..............................................5-11
Engine Compartment Overview.......................5-12
Engine Oil...................................................5-16
Engine Air Cleaner/Filter................................5-21
Automatic Transmission Fluid.........................5-23
Engine Coolant.............................................5-26
Coolant Surge Tank Pressure Cap..................5-28
Engine Overheating.......................................5-29Cooling System............................................5-32
Engine Fan Noise.........................................5-38
Power Steering Fluid.....................................5-38
Windshield Washer Fluid................................5-40
Brakes........................................................5-41
Battery........................................................5-44
Jump Starting...............................................5-45
All-Wheel Drive..............................................5-51
Rear Axle.......................................................5-52
Four-Wheel Drive............................................5-53
Front Axle......................................................5-54
Bulb Replacement..........................................5-55
Halogen Bulbs..............................................5-55
Headlamps..................................................5-55
Front Turn Signal, Sidemarker and Daytime
Running Lamps.........................................5-56
Side Identication Marker Lamps.....................5-57
Roof Marker Lamps......................................5-58
Taillamps.....................................................5-60
Replacement Bulbs.......................................5-61
Section 5 Service and Appearance Care
5-1

Automatic Transmission Fluid
When to Check and Change
A good time to check your automatic transmission uid
level is when the engine oil is changed.
Change both the uid and lter every 50,000 miles
(83 000 km) if the vehicle’s GVWR is over 8,600 or if
the vehicle is mainly driven under one or more of these
conditions:
In heavy city traffic where the outside temperature
regularly reaches 90°F (32°C) or higher.
In hilly or mountainous terrain.
When doing frequent trailer towing.
Uses such as found in taxi, police or delivery
service.
If your vehicle’s GVWR is not over 8,600 and you do
not use your vehicle under any of these conditions,
change the uid and lter every 100,000 miles
(166 000 km).
SeeScheduled Maintenance on page 6-4.
How to Check
Because this operation can be a little difficult, you may
choose to have this done at the dealership service
department.
If you do it yourself, be sure to follow all the instructions
here, or you could get a false reading on the dipstick.
Notice:Too much or too little uid can damage
your transmission. Too much can mean that some
of the uid could come out and fall on hot engine
part or exhaust system parts, starting a re.
Too little uid could cause the transmission to
overheat. Be sure to get an accurate reading if you
check your transmission uid.
Wait at least 30 minutes before checking the
transmission uid level if you have been driving:
When outside temperatures are above 90°F (32°C).
At high speed for quite a while.
In heavy traffic – especially in hot weather.
While pulling a trailer.
To get the right reading, the uid should be at normal
operating temperature, which is 180°F to 200°F
(82°C to 93°C).
5-23

Engine Coolant
The cooling system in your vehicle is lled 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 rst, 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, seeEngine Overheating on
page 5-29.
A 50/50 mixture of clean, drinkable water and
DEX-COOL
®coolant will:
Give freezing protection down to−34°F (−37°C).
Give boiling protection up to 265°F (129°C).
Protect against rust and corrosion.
Help keep the proper engine temperature.
Let the warning lights and gages work as they
should.
Notice:Using coolant other than DEX-COOL
®may
cause premature engine, heater core or radiator
corrosion. In addition, the engine coolant may
require changing sooner, at 30,000 miles (50 000 km)
or 24 months, whichever occurs rst. Any repairs
would not be covered by your warranty. Always use
DEX-COOL
®(silicate-free) coolant in your vehicle.
What to Use
Use a mixture of one-halfclean, drinkable waterand
one-half DEX-COOL®coolant which won’t damage
aluminum parts. If you use this coolant mixture,
you don’t need to add anything else.
{CAUTION:
Adding only plain water to your cooling
system can be dangerous. Plain water, or
some other liquid such as alcohol, can boil
before the proper coolant mixture will. Your
vehicle’s coolant warning system is set for the
proper coolant mixture. With plain water or the
wrong mixture, your engine could get too hot
but you would not get the overheat warning.
Your engine could catch re and you or others
could be burned. Use a 50/50 mixture of clean,
drinkable water and DEX-COOL
®coolant.
5-26

Notice:If you use an improper coolant mixture,
your engine could overheat and be badly damaged.
The repair cost would not be covered by your
warranty. Too much water in the mixture can freeze
and crack the engine, radiator, heater core and
other parts.
If you have to add coolant more than four times a year,
have your dealer check your cooling system.
Notice:If you use the proper coolant, you do not
have to add extra inhibitors or additives which claim
to improve the system. These can be harmful.
Checking Coolant
The coolant surge tank is
located in the engine
compartment on the
passenger’s side of the
vehicle. SeeEngine
Compartment Overview on
page 5-12for more
information on location.
{CAUTION:
Turning the surge tank pressure cap when the
engine and radiator are hot can allow steam
and scalding liquids to blow out and burn you
badly. Never turn the surge tank pressure
cap — even a little — when the engine and
radiator are hot.
The vehicle must be on a level surface. When your
engine is cold, the coolant level should be at the
FULL COLD mark.
If your vehicle is equipped with a low coolant sensor,
and the LOW COOLANT LEVEL message comes
on and stays on, it means you’re low on engine coolant.
See “Low Coolant Level” underDIC Warnings and
Messages on page 3-70.
5-27

Engine Overheating
You will nd a coolant temperature gage on your
vehicle’s instrument panel. SeeEngine Coolant
Temperature Gage on page 3-49. In addition, you will
nd an ENGINE OVERHEATED, and a REDUCED
ENGINE POWER message in the DIC on the instrument
panel. SeeDriver Information Center (DIC) on
page 3-58.
Overheated Engine Protection
Operating Mode (V8 Engines Only)
If an overheated engine condition exists and the
REDUCED ENGINE POWER 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 5-16.
5-29