2003 GMC YUKON DENALI Owners Manual

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 don’t
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.
.
1 ~ ---lg the surge tanl- ,xessure 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 the LOW COOLANT
LEVEL message comes on and
stays on, it means you’re low on engine coolant.
See “Low Coolant Level” under
DIC Warnings and
Messages on page
3-52.
See Engine Compartment Overview on page 5-12 for
more information on location.
5-24

Adding Coolant
If you need more coolant, add the proper DEX-COOL@
coolant mixture
at the surge tank, but only when the
engine
is cool.
1 “J can be burned if you sb... coolant on hot
engine parts. Coolant contains ethylene glycol, and
it will burn if the engine parts are hot
enough. Don’t spill coolant on a hot engine.
When replacing the pressure cap, make sure it is
hand-tight.
Coolant Surge Tank Pressure Cap
The coolant surge tank pressure cap must be fully
installed on the coolant surge tank. See Engine
Compartment Overview on page
5-12 for more
information on location.
Notice: Your pressure cap is a pressure-type cap
and must be tightly installed to prevent coolant
loss
and possible engine damage from overheating.
See “Capacities and Specifications” for more
information.
Engine Overheating
You will find a coolant temperature gage on your
vehicle’s instrument panel. See Engine Coolant
Temperature Gage
on page 3-36. in addition, yoti ill
find a LOW COOLANT, ENGINE COOLANT HOT,
ENGINE OVERHEATED and a REDUCED ENGINE
POWER message in the DIC on the instrument panel.
See DIC Warnings and Messages on page
3-52.
Overheated Engine Protection
Operating Mode
If an overheated engine condition exists and the
REDUCED ENGINE POWER message is displayed, an
overheat protection mode which alternates firing
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. See “Engine Oil” in the Index.
5-25

If Steam Is Coming From Your Engine
L
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. Just turn it off and get
everyone away from the vehicle until
it cools
CAUTION: (Continued) down. Wait until there
is no sign of steam or
coolant before you open the hood.
If you
keep driving when your engine is
overheated, the liquids in it can catch fire. You
or others could be badly burned. Stop your
engine if
it overheats, and get out of the
vehicle until the engine is cool.
See “Overheated Engine Protection Operating
Mode” in the Index for information on driving
to a safe place
in an emergency.
Notice: If your engine catches fire because you
keep driving with no coolant, your vehicle can
be badly damaged. The costly repairs would not be
covered by your warranty. See “Overheated
Engine Protection Operating Mode” in the Index for
information on driving to a safe place in an
emergency.
5-26

If No Steam Is Coming From Your
Engine
An overheat warning, along with a low coolant message,
can indicate a serious problem. See
Low Coolant
Level Warning Message under DIC Warnings and
Messages
on page 3-52.
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:
0 Climb a long hill on a hot day.
Stop after high-speed driving.
0 Idle for long periods in traffic.
0 Tow a trailer. See Towing a Trailer on page 4-47.
If you get the overheat warning with no sign of steam, try
this for a minute or so:
1. Turn on your heater to full hot at the highest fan
speed and open the window as necessary.
If you no longer have the overheat warning, you can
drive. Just
to be safe, drive slower for about 10 minutes.
If the warning doesn’t come back on, you can drive
normally.
If the warning continues, pull over, stop, and park your
vehicle right away.
If there’s still no sign of steam, push down the
accelerator until the engine speed is about twice as fast
as normal idle speed for at least three minutes while
you’re 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” listed previously in this section.
You may decide not
to lift the hood but to get service
help right away.
2. If you’re in a traffic jam, shift to NEUTRAL (N);
otherwise, shift to the highest gear while
driving
- DRIVE (D).
5-27

Cooling System
When you decide it’s safe to lift the hood, here’s what
you’ll see: If the
coolant inside the coolant surge tank
is boiling,
don’t do anything else until
it cools down. The vehicle
should be parked on a level surface.
A. Coolant Surge Tank
B. Coolant Surge Tank Pressure Cap
C. Engine Fan
1
The coolant level should
be at or above the FULL
COLD mark. If
it isn’t,
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.
5-28

Heater and rac.-:or hoses, and other engine
parts, can be very hot. Don’t touch them. If you
do, you can be burned.
Don’t 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.
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 doesn’t, your vehicle needs service. Turn
off
the engine.
Notice: Engine damage from running your engine
without coolant isn’t covered by your warranty.
See “Overheated Engine Protection Operating
Mode”
in the Index for information on driving to a
safe place
in an emergency.
Notice: When adding coolant, it is important that
you use only
DEX-COOL@ (silicate-free) coolant.
If coolant other than DEX-COOL@ is added to
the system, premature engine, heater core or radiator corrosion
may result. In addition, the engine
coolant will require change sooner
- at 30,000 miles
(50 000 km) or 24 months, whichever occurs first.
Damage caused by
the use of coolant other
than DEX-COOL@ is not covered by your new vehicle
warranty.
How to Add Coolant to the Coolant
Surge Tank
If you haven’t found a problem yet, check to see if
coolant is visible in the surge tank. If coolant is visible
but the coolant level isn’t 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. See Engine Coolant on
page 5-22 for more
information.
If no coolant is visible in the surge tank, add coolant as
follows:
5-29

Steam and scalding liquids f I hl 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.
5-30

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 wouldn't get the overheat warning.
Your engine could catch fire 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. You can be burned
if you spill coolant on tist
engine parts. Coolant contains ethylene glycol
and
it will burn if the engine parts are hot
enough. Don't
spill coolant on a hot engine.
1. Park the vehicle on a
level surface.
SURGE RESERVOIR
15 PSI
TANK - 105 kPa
D'EXPANSION I
You
can 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
(left) about one full turn. If you hear a hiss, wait for
that
to stop. A hiss means there is still some
pressure left.
5-31