2004 GMC SIERRA cooling

Trailer Brakes
If your trailer weighs more than 2,000 lbs. (900 kg)
loaded, then it needs its own brakes ± and they must be
adequate. Be sure to read and follow the instructions
for the trailer brakes so you'll be able to install,
adjust and maintain them properly.
Your trailer brake system can tap into the vehicle's
hydraulic brake system only if:
·The trailer parts can withstand 3,000 psi
(20 650 kPa) of pressure.
·The trailer's brake system will use less than
0.02 cubic inch (0.3 cc) of ¯uid from your vehicle's
master cylinder. Otherwise, both braking systems
won't work well. You could even lose your brakes.
If everything checks out this far, make the brake tap at
the port on the master cylinder that sends the ¯uid
to the rear brakes. But don't use copper tubing for this.
If you do, it will bend and ®nally break off. Use steel
brake tubing.
Driving with a Trailer
{CAUTION:
If you have a rear-most window open and you
pull a trailer with your vehicle, carbon
monoxide (CO) could come into your vehicle.
You can not see or smell CO. It can cause
unconsciousness or death. See
Engine
Exhaust on page 2-53
. To maximize your safety
when towing a trailer:
·Have your exhaust system inspected for
leaks, and make necessary repairs before
starting on your trip.
·Keep the rear-most windows closed.
·If exhaust does come into your vehicle
through a window in the rear or another
opening, drive with your front, main
heating or cooling system on and with the
fan on any speed. This will bring fresh,
outside air into your vehicle. Do not use
the climate control setting for maximum air
because it only recirculates the air inside
your vehicle. See
Climate Control System
on page 3-21.
4-91

When You Are Ready to Leave After
Parking on a Hill
1. Apply your regular brakes and hold the pedal down
while you:
·Start your engine
·Shift into a gear
·Release the parking brake
2. Let up on the brake pedal.
3. Drive slowly until the trailer is clear of the chocks.
4. Stop and have someone pick up and store the
chocks.
Maintenance When Trailer Towing
Your vehicle will need service more often when you're
pulling a trailer. SeeScheduled Maintenance on
page 6-4for more information. Things that are especially
important in trailer operation are automatic transmission
¯uid (don't over®ll), engine oil, axle lubricant, belt,
cooling system and brake system. Each of these is
covered in this manual, and the Index will help you ®nd
them quickly. If you're trailering, it's a good idea to
review these sections before you start your trip.
Check periodically to see that all hitch nuts and bolts
are tight.
Trailer Wiring Harness
Your vehicle is equipped with one of the following wiring
harnesses for towing a trailer or hauling a slide-in
camper.
Basic Trailer Wiring
All regular, extended cab crew cab pickups have a
six-wire trailer towing harness.
The six-wire harness is located at the rear of the vehicle
and is tied to the vehicle's frame. The harness requires
the installation of a trailer-wiring harness connector,
which is available through your dealer.
4-95

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 Speci®cations....................................5-5
California Fuel...............................................5-5
Additives.......................................................5-6
Fuels in Foreign Countries...............................5-6
Filling Your Tank............................................5-7
Filling a Portable Fuel Container.......................5-9
Checking Things Under the Hood....................5-10
Hood Release..............................................5-10
Engine Compartment Overview.......................5-12
Engine Oil...................................................5-18
Engine Air Cleaner/Filter................................5-23
Automatic Transmission Fluid (Except Allison
Transmission
ž) ..........................................5-25
Automatic Transmission Fluid (Allison
Transmission
ž) ..........................................5-28
Manual Transmission Fluid.............................5-31
Hydraulic Clutch...........................................5-32
Engine Coolant.............................................5-33
Coolant Surge Tank Pressure Cap..................5-36
Engine Overheating.......................................5-36Cooling System............................................5-39
Engine Fan Noise.........................................5-44
Power Steering Fluid.....................................5-45
Windshield Washer Fluid................................5-46
Brakes........................................................5-48
Battery........................................................5-52
Jump Starting...............................................5-53
Rear Axle.......................................................5-59
Four-Wheel Drive............................................5-60
Noise Control System.....................................5-62
Tampering with Noise Control System
Prohibited.................................................5-62
Bulb Replacement..........................................5-64
Halogen Bulbs..............................................5-64
Headlamps..................................................5-64
Front Turn Signal, Sidemarker and Daytime
Running Lamps.........................................5-66
Roof Marker Lamps......................................5-67
Center High-Mounted Stoplamp (CHMSL) and
Cargo Lamp.............................................5-69
Pickup Box Identi®cation and Fender Marker
Lamps.....................................................5-70
Taillamps.....................................................5-71
Replacement Bulbs.......................................5-74
Section 5 Service and Appearance Care
5-1

A. Engine Air Cleaner/Filter. SeeEngine Air
Cleaner/Filter on page 5-23.
B. Coolant Surge Tank. See
Engine Coolant on
page 5-33.
C. Air Filter Restriction Indicator (If Equipped). See
Engine Air Cleaner/Filter on page 5-23.
D. Engine Oil Dipstick. See
Engine Oil on page 5-18.
E. Automatic Transmission Dipstick (If equipped).
See
Automatic Transmission Fluid (Except Allison
Transmissionž) on page 5-25orAutomatic
Transmission Fluid (Allison Transmissionž)on
page 5-28.
F. Fan. See
Cooling System on page 5-39.
G. Engine Oil Fill. See
Engine Oil on page 5-18.H. Power Steering Fluid Reservoir. See
Power Steering
Fluid on page 5-45.
I. Remote Negative (-) Terminal (GND). See
Jump
Starting on page 5-53.
J. Remote Positive (+) Terminal. See
Jump Starting on
page 5-53.
K. Brake Fluid Reservoir. See
Brakes on page 5-48.
L. Clutch Fluid Reservoir (If Equipped). See
Hydraulic
Clutch on page 5-32.
M. Underhood Fuse Block. See
Fuses and Circuit
Breakers on page 5-126.
N. Battery. See
Battery on page 5-52.
O. Windshield Washer Fluid Reservoir. See
Windshield
Washer Fluid on page 5-46.
5-13

A. Engine Air Cleaner/Filter. SeeEngine Air
Cleaner/Filter on page 5-23.
B. Coolant Surge Tank. See
Engine Coolant on
page 5-33.
C. Air Filter Restriction Indicator (If Equipped). See
Engine Air Cleaner/Filter on page 5-23.
D. Engine Oil Dipstick. See
Engine Oil on page 5-18.
E. Automatic Transmission Dipstick (If Equipped).
See
Automatic Transmission Fluid (Except Allison
Transmissionž) on page 5-25orAutomatic
Transmission Fluid (Allison Transmissionž)on
page 5-28.
F. Engine Oil Fill. See
Engine Oil on page 5-18.
G. Fan. See
Cooling System on page 5-39.H. Remote Negative (-) Terminal (GND). See
Jump
Starting on page 5-53.
I. Power Steering Fluid Reservoir. See
Power Steering
Fluid on page 5-45.
J. Remote Positive (+) Terminal. See
Jump Starting on
page 5-53.
K. Brake Fluid Reservoir. See
Brakes on page 5-48.
L. Clutch Fluid Reservoir (If Equipped). See
Hydraulic
Clutch on page 5-32.
M. Underhood Fuse Block. See
Fuses and Circuit
Breakers on page 5-126.
N. Battery. See
Battery on page 5-52.
O. Windshield Washer Fluid Reservoir. See
Windshield
Washer Fluid on page 5-46.
5-15

A. Engine Air Cleaner/Filter. SeeEngine Air
Cleaner/Filter on page 5-23.
B. Coolant Surge Tank. See
Engine Coolant on
page 5-33.
C. Air Filter Restriction Indicator (If Equipped). See
Engine Air Cleaner/Filter on page 5-23.
D. Engine Oil Dipstick. See
Engine Oil on page 5-18.
E. Automatic Transmission Dipstick (If Equipped).
See
Automatic Transmission Fluid (Except Allison
Transmissionž) on page 5-25orAutomatic
Transmission Fluid (Allison Transmissionž)on
page 5-28.
F. Engine Oil Fill. See
Engine Oil on page 5-18.
G. Fan. See
Cooling System on page 5-39.H. Remote Negative (-) Terminal (GND). See
Jump
Starting on page 5-53.
I. Remote Positive (+) Terminal. See
Jump Starting on
page 5-53.
J. Power Steering Fluid Reservoir. See
Power Steering
Fluid on page 5-45.
K. Brake Fluid Reservoir. See
Brakes on page 5-48.
L. Clutch Fluid Reservoir (If Equipped). See
Hydraulic
Clutch on page 5-32.
M. Underhood Fuse Block. See
Fuses and Circuit
Breakers on page 5-126.
N. Battery. See
Battery on page 5-52.
O. Windshield Washer Fluid Reservoir. See
Windshield
Washer Fluid on page 5-46.
5-17

How to Check and Add Fluid
The proper ¯uid should be added if the level does not
reach the bottom of the diaphragm when it's in place in
the reservoir. See the instructions on the reservoir cap.
Engine Coolant
The cooling system in your vehicle is ®lled with
DEX-COOLžengine 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
žextended 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
Engine Overheating on
page 5-36.A 50/50 mixture of clean, drinkable water and
DEX-COOL
žcoolant will:
·Give freezing protection down to-34ÉF (-37ÉC).
·Give boiling protection up to 265ÉF (129ÉC).
·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-COOLžmay
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
ž(silicate-free) coolant in your vehicle.
5-33

What to Use
Use a mixture of one-halfclean, drinkable waterand
one-half DEX-COOLžcoolant 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
žcoolant.
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.
5-34