2003 CHEVROLET TAHOE cooling

Notice:If you use an improper coolant mixture,
your engine could overheat and be badly damaged.
The repair cost wouldn't 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 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. See
Engine
Compartment Overview on
page 5-14
for 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 Ð even a little Ð 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 ªLow Coolant Levelº under
DIC Warnings and
Messages on page 3-64.
5-31

Cooling System
When you decide it's safe to lift the hood, here's what
you'll see:
A. Coolant Surge Tank
B. Coolant Surge Tank Pressure Cap
C. Engine Fan
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. 8100 V8 Engines
All Other Engines
5-36

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.
{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.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 ªOverheated Engine Protection Operating
Modeº 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-COOLž(silicate-free) coolant.
If coolant other than DEX-COOLžis added to
the system, premature engine, heater core or
radiator corrosion may result. In addition, the engine
coolant will require change sooner Ð at 30,000 miles
(50 000 km) or 24 months, whichever occurs ®rst.
Damage caused by the use of coolant other
than DEX-COOL
žis not covered by your new vehicle
warranty.
5-37

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
waterand DEX-COOLžcoolant 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 5-29for more
information.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 coolant
surge tank pressure cap Ð even a little Ð 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.
5-38

{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
žcoolant.
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.
5-39

{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. Park the vehicle on a
level surface. 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.2. 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.
3. Then keep turning the pressure cap slowly, and
remove it.
5-40

4. Then ®ll the coolant surge tank with the proper
mixture, to the FULL COLD mark.5. 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.
5-41

6. Then replace the
pressure cap. Be sure
the pressure cap is
hand-tight and
fully seated.Engine Fan Noise
Your 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 loading, trailer
towing and/or high outside temperatures, the fan
speed increases as the clutch more fully engages. So
you may hear an increase in fan noise. 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.
You may also hear this fan noise when you start the
engine. It will go away as the fan clutch partially
disengages.
5-42