2003 GMC SIERRA engine

1. Loosen the screws on the cover of the housing and
lift up the cover.
2. Remove the air cleaner/filter from the housing. Care
should be taken to dislodge as little dirt as possible.
3. Clean thefilter sealing surface and the housing.
4. Install the new engine air cleaner/filter.
5. Reinstall the cover and tighten the screws.
{CAUTION:
Operating the engine with the air cleaner/filter
off can cause you or others to be burned. The
air cleaner not only cleans the air, it helps to
stopflame if the engine backfires. If it isn’t there
and the engine backfires, you could be burned.
Don’t drive with it off, and be careful working on
the engine with the air cleaner/filter off.
Notice:If the air cleaner/filter is off, a backfire can
cause a damaging enginefire. And, dirt can
easily get into your engine, which will damage it.
Always have the air cleaner/filter in place when
you’re driving.
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2003 - Sierra Denali

Automatic Transmission Fluid
When to Check and Change
A good time to check your automatic transmissionfluid
level is when the engine oil is changed.
Change both thefluid andfilter every 50,000 miles
(83 000 km) if the vehicle is mainly driven under one or
more of these conditions:
•In heavy city traffic where the outside temperature
regularly reaches 90°F (32°C) or higher.
•In hilly or mountainous terrain.
•When doing frequent trailer towing.
•Uses such as found in taxi, police or delivery
service.
If you do not use your vehicle under any of these
conditions, change thefluid andfilter every
100,000 miles (166 000 km).
SeePart A: Scheduled Maintenance Services on
page 6-4.
How to Check
Because this operation can be a little difficult, you may
choose to have this done at the dealership service
department.
If you do it yourself, be sure to follow all the instructions
here, or you could get a false reading on the dipstick.
Notice:Too much or too littlefluid can damage
your transmission. Too much can mean that some
of thefluid could come out and fall on hot engine
part or exhaust system parts, starting afire.
Too littlefluid could cause the transmission to
overheat. Be sure to get an accurate reading if you
check your transmissionfluid.
Wait at least 30 minutes before checking the
transmissionfluid level if you have been driving:
•When outside temperatures are above 90°F (32°C).
•At high speed for quite a while.
•In heavy traffic–especially in hot weather.
•While pulling a trailer.
To get the right reading, thefluid should be at normal
operating temperature, which is 180°Fto200°F
(82°Cto93°C).
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2003 - Sierra Denali

Get the vehicle warmed up by driving about 15 miles
(24 km) when outside temperatures are above 50°F
(10°C).Ifit’s colder than 50°F (10°C), drive the vehicle
in THIRD (3) until the engine temperature gage
moves and then remains steady for 10 minutes.
A coldfluid check can be made after the vehicle has
been sitting for eight hours or more with the engine off,
but this is used only as a reference. Let the engine
run at idle forfive minutes if outside temperatures are
50°F (10°C) or more. If it’s colder than 50°F (10°C), you
may have to idle the engine longer. Should thefluid
level be low during this cold check, youmustcheck the
fluid hot before addingfluid. Checking thefluid hot
will give you a more accurate reading of thefluid level.
Checking the Fluid Level
Prepare your vehicle as follows:
•Park your vehicle on a level place. Keep the engine
running.
•With the parking brake applied, place the shift lever
in PARK (P).
•With your foot on the brake pedal, move the shift
lever through each gear range, pausing for about
three seconds in each range. Then, position the shift
lever in PARK (P).
•Let the engine run at idle for three minutes or more.Then, without shutting off the engine, follow these steps:
The transmission dipstick handle is located at the rear
of the engine compartment, on the passenger’s
side. SeeEngine Compartment Overview on page 5-12
for further information on location.
1. Flip the handle up and then pull out the dipstick
and wipe it with a clean rag or paper towel.
2. Push it back in all the way, wait three seconds and
then pull it back out again.
5-21
2003 - Sierra Denali

Engine Coolant
The cooling system in your vehicle isfilled 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 occursfirst, 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, seeEngine Overheating on
page 5-26.
A 50/50 mixture of clean, drinkable water and
DEX-COOL
®coolant will:
•Give freezing protection down to−34°F(−37°C).
•Give boiling protection up to 265°F (129°C).
•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 occursfirst.
Damage caused by the use of coolant other
than DEX-COOL
®is not covered by your new vehicle
warranty.
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2003 - Sierra Denali

What to Use
Use a mixture of one-halfclean, drinkable waterand
one-half DEX-COOL®coolant 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 wouldn’t get the overheat warning.
Your engine could catchfire and you or others
could be burned. Use a 50/50 mixture of clean,
drinkable water and DEX-COOL
®coolant.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. SeeEngine
Compartment Overview on
page 5-12for more
information on location.
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2003 - Sierra Denali

{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—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”underDIC Warnings and
Messages on page 3-51.
Adding Coolant
If you need more coolant, add the proper DEX-COOL®
coolant mixtureat the surge tank, but only when the
engine is cool.
{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.
When replacing the pressure cap, make sure it is
hand-tight.
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2003 - Sierra Denali

Coolant Surge Tank Pressure Cap
The coolant surge tank
pressure cap must be fully
installed on the coolant
surge tank.
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 willfind a coolant temperature gage on your
vehicle’s instrument panel. SeeEngine Coolant
Temperature Gage on page 3-36. In addition, you will
find a LOW COOLANT, ENGINE OVERHEATED and a
REDUCED ENGINE POWER message in the DIC on
the instrument panel. SeeDriver Information Center
(DIC) on page 3-42.
Overheated Engine Protection
Operating Mode
If an overheated engine condition exists and the
REDUCED ENGINE POWER message is displayed, an
overheat protection mode which alternatesfiring
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.
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2003 - Sierra Denali

If Steam Is Coming From Your Engine
{CAUTION:
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 down.
CAUTION: (Continued)
CAUTION: (Continued)
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 catchfire.
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 catchesfire 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.
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2003 - Sierra Denali