2002 GMC YUKON radiator

2-81
At approximately 265
F (130
C), the message center
will display a TRANS FLUID HOT message and the
transmission will enter a transmission protection mode.
When the transmission enters the protection mode, you
may notice a change in the transmission shifting
patterns. The transmission will return to normal shifting
patterns when the transmission fluid temperature falls
below 260
F (127
C).
See ªMessage Centerº in the Index for
further information.
If the transmission fluid reaches temperatures of
approximately 275
F (135
C) or greater, the message
center will display a TRANS HOT...IDLE ENG warning
message. Pull the vehicle off the roadway when it is safe
to do so. Set the parking brake, place the transmission in
PARK (P) and allow the engine to idle until the
transmission temperature falls below 260
F (127
C).
If the transmission continues to operate above 265
F
(130
C), contact your nearest dealer or the GM
Roadside Assistance Center. See ªRoadside Assistanceº
in the Index.
NOTICE:
If you keep driving your vehicle with the
transmission temperature gage above the
normal operating range, you can damage the
transmission. This could lead to costly repairs
that may not be covered under your warranty.
The following situations can cause the transmission to
operate at higher temperatures:

Towing a trailer

Hot outside air temperatures

Hauling a large or heavy load

Low transmission fluid level

High transmission fluid level

Restricted air flow to the radiator and the auxiliary
transmission oil cooler (if equipped).
A temporary solution to hotter transmission operating
temperatures may be to let the transmission cool down.
If the transmission is operated at higher temperatures on
a frequent basis, see ªScheduled Maintenanceº in the
Index for the proper transmission maintenance intervals.

2-89 Trans Fluid Hot
If you have an automatic transmission, you have a
transmission temperature warning display contained in
the message center.
If the transmission
fluid temperature
becomes high, the
message will be displayed.
When the transmission enters the protection mode, you
may notice a change in the transmission shifting
patterns. When the transmission fluid temperature
returns to normal, the display will turn off and the
transmission shifting patterns will return to normal.
NOTICE:
If you keep driving your vehicle with the
transmission TRANS FLUID HOT message
displayed, you can damage the transmission.
This could lead to costly repairs that may not be
covered under your warranty.
The following situations can cause the transmission to
operate at higher temperatures:

Towing a trailer

Hot outside air temperatures

Hauling a large or heavy load

Low transmission fluid level

High transmission fluid level

Restricted air flow to the radiator and the auxiliary
transmission oil cooler (if equipped).
A temporary solution to hotter transmission operating
temperatures may be to let the transmission cool down.
If the transmission is operated at higher temperatures on
a frequent basis, see ªScheduled Maintenanceº in the
Index for the proper transmission maintenance intervals.

2-90 Trans Hot...Idle Engine
Your vehicle has a transmission over-temperature
display contained in the message center.
If this warning message is
displayed, pull the vehicle
off the roadway when it is
safe to do so.
Set the parking brake and place the transmission in
PARK (P). Idle the engine until the message center no
longer displays a message. If idling the engine does not
turn the warning message off after 10 to 15 minutes,
contact your nearest dealer or the GM Roadside
Assistance Center. See ªRoadside Assistanceº
in the Index.
NOTICE:
If you keep driving your vehicle with the
transmission TRANS HOT...IDLE ENGINE
message displayed, you can damage the
transmission. This could lead to costly repairs
that may not be covered under your warranty.
The following situations can cause the transmission to
operate at higher temperatures:

Towing a trailer

Hot outside air temperatures

Hauling a heavy load

Low transmission fluid level

High transmission fluid level

Restricted air flow to the radiator and the auxiliary
transmission oil cooler (if equipped).
A temporary solution to hotter transmission operating
temperatures may be to let the transmission cool down.
If the transmission is operated at higher temperatures on
a frequent basis, see ªScheduled Maintenanceº in the
Index for the proper transmission maintenance intervals.

5-13
The coolant level
should be at or above
the FILL 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. 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 ªOverheated Engine Protection Operating
Modeº in the Index.
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.

5-15
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 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. So
use the recommended coolant.
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. Don't spill coolant on a hot engine.

5-16
Your vehicle may be
equipped with one of
the two caps shown.
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. 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.
2. Then keep turning the pressure cap slowly, and
remove it.
3. Then fill the coolant surge tank with the proper
mixture, to the FILL COLD mark.

5-17
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 FILL COLD mark.5. Then replace the pressure cap. Be sure the pressure
cap is hand
-tight and fully seated.

6-31
Engine Coolant
The cooling system in your vehicle is filled 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 first, 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, see ªEngine Overheatingº in
the Index.
A 50/50 mixture of clean, drinkable water and
DEX
-COOL coolant will:

Give freezing protection down to
-34F (-37C).

Give boiling protection up to 265F (129C).

Protect against rust and corrosion.

Help keep the proper engine temperature.

Let the warning lights and gages work as
they should.
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.