GMC YUKON 2007 Owner's Manual

Cooling System
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{CAUTION:
An electric engine cooling fan under the
hood can start up even when the engine
is not running and can injure you. 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.
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.
451

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.
452

Notice:Engine damage from running your
engine without coolant is not covered by your
warranty. SeeOverheated Engine Protection
Operating Mode on page 450for information on
driving to a safe place in an emergency.
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.
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 445for more information.
453

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 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.
{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.
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.
454

{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.
1. 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.
Remove the coolant surge tank pressure
cap by slowly turning the pressure cap
counterclockwise about one full turn. If you
hear a hiss, wait for that to stop. A hiss means
there is still some pressure left.2. Then keep turning the pressure cap slowly,
and remove it.
3. Fill the coolant surge tank with the proper
mixture, to the FULL COLD mark.
455

4. With the coolant surge tank pressure cap off,
start the engine and let it run until you can
feel the upper radiator hose getting hot. Watch
out for the engine cooling fan.
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. Then replace the pressure cap. Be sure the
pressure cap is hand-tight and fully seated.
6. Verify coolant level after engine is shut off
and the coolant is cold. If necessary, repeat
coolant ll procedure steps 1 through 6.
Engine Fan Noise
Your vehicle has electric cooling fans, you may
hear the fans spinning at low speed during
most everyday driving. The fans may turn off if no
cooling is required. Under heavy vehicle loading,
trailer towing, and/or high outside temperatures, or
if you are operating your air conditioning system,
the fans may change to high speed and you
may hear an increase in fan noise. This is normal
and indicates that the cooling system is
functioning properly. The fans will change to low
speed when additional cooling is no longer
required.
456

Power Steering Fluid
SeeEngine
Compartment Overview
on page 430for
reservoir location.
When to Check Power Steering Fluid
It is not necessary to regularly check power
steering uid unless you suspect there is a leak in
the system or you hear an unusual noise. A
uid loss in this system could indicate a problem.
Have the system inspected and repaired.
How to Check Power Steering Fluid
To check the power steering uid, do the following:
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
uid level on the dipstick.
The level should be at the FULL COLD mark.
If necessary, add only enough uid to bring
the level up to the mark.
What to Use
To determine what kind of uid to use, see
Recommended Fluids and Lubricants on page 561.
Always use the proper uid. Failure to use the
proper uid can cause leaks and damage hoses
and seals.
457

Windshield Washer Fluid
What to Use
When you need windshield washer uid, be sure to
read the manufacturer’s instructions before use. If
you will be operating your vehicle in an area where
the temperature may fall below freezing, use a uid
that has sufficient protection against freezing.
Adding Washer Fluid
Your vehicle has a message that comes on when
the washer uid is low. The message is
displayed for 15 seconds at the start of each
ignition cycle. When the CHECK WASHER FLUID
message is displayed, you will need to add
washer uid to the windshield washer uid
reservoir. SeeDIC Warnings and Messages on
page 252for more information.
Open the cap with the
washer symbol on it.
Add washer uid
until the tank is full. See
Engine Compartment
Overview on page 430
for reservoir location.Notice:
When using concentrated washer uid,
follow the manufacturer’s instructions
for adding water.
Do not mix water with ready-to-use washer
uid. Water can cause the solution to
freeze and damage your washer uid tank
and other parts of the washer system.
Also, water does not clean as well
as washer uid.
Fill your washer uid tank only
three-quarters full when it is very cold.
This allows for expansion if freezing
occurs, which could damage the tank if it
is completely full.
Do not use engine coolant (antifreeze) in
your windshield washer. It can damage
your washer system and paint.
458

Brakes
Brake Fluid
Your brake master
cylinder reservoir is
lled with DOT-3 brake
uid. SeeEngine
Compartment Overview
on page 430for the
location of the reservoir.
There are only two reasons why the brake uid
level in the reservoir might go down. The rst
is that the brake uid goes down to an acceptable
level during normal brake lining wear. When
new linings are put in, the uid level goes back
up. The other reason is that uid is leaking out of
the brake system. If it is, you should have your
brake system xed, since a leak means that
sooner or later your brakes will not work well,
or will not work at all.So, it is not a good idea to top off your brake uid.
Adding brake uid will not correct a leak. If you
add uid when your linings are worn, then you will
have too much uid when you get new brake
linings. You should add or remove brake uid,
as necessary, only when work is done on
the brake hydraulic system.
{CAUTION:
If you have too much brake uid, it can spill
on the engine. The uid will burn if the
engine is hot enough. You or others could
be burned, and your vehicle could be
damaged. Add brake uid only when work
is done on the brake hydraulic system.
See “Checking Brake Fluid” in this section.
When the brake uid falls to a low level, the brake
warning light will come on. SeeBrake System
Warning Light on page 233.
Refer to the Maintenance Schedule to determine
when to check your brake uid. SeeScheduled
Maintenance on page 551.
459

Checking Brake Fluid
You can check the brake uid without taking off
the cap.
Look at the brake uid
reservoir. The uid level
should be above
MIN. If it is not, have
your brake system
checked to see if there
is a leak.
After work is done on the brake hydraulic system,
make sure the level is above the MIN but not
over the MAX mark.
What to Add
When you do need brake uid, use only DOT-3
brake uid. Use new brake uid from a sealed
container only. SeeRecommended Fluids
and Lubricants on page 561.
Always clean the brake uid reservoir cap and the
area around the cap before removing it. This
will help keep dirt from entering the reservoir.
{CAUTION:
With the wrong kind of uid in your brake
system, your brakes may not work well, or
they may not even work at all. This could
cause a crash. Always use the proper
brake uid.
460