tow GMC SIERRA CLASSIC 2007 Owners Manual

3. With your foot on the brake pedal, run the
engine for at least once minute and shift to
DRIVE (D). Then shift to NEUTRAL (N) and
then REVERSE (R) to ll the hydraulic system.
Then, position the shift lever in PARK (P).
4. Allow the engine to run at idle (500–800 rpm).
Slowly release the brake pedal.
Then, without shutting off the engine, follow
these steps:
Cold Check Procedure
The purpose of the cold check is to determine if the
transmission has enough uid to be operated safely
until a hot check can be made. The uid level rises
as uid temperature increases. Do not ll above the
COLD CHECK band if the transmission uid is
below normal operating temperatures.
1. 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.
3. Check the uid level reading. Repeat the
check procedure to verify the reading.4. If the uid level is within the COLD CHECK
band, the transmission may be operated until
the uid is hot enough to perform a hot
check. If the uid level is not within the COLD
CHECK band, add or drain uid as necessary
to bring the level into the middle of the
COLD CHECK band.
5. Perform a hot check at the rst opportunity
after the normal operating temperature of
160°F (71°C) to 200°F (93°C) is reached.
6. If the uid level is in the acceptable range,
push the dipstick back in all the way.
495

Hot Check Procedure
The uid must be hot to ensure an accurate
check. The uid level rises as the temperature
increases.
1. Operate the transmission in DRIVE (D) range
until the normal operating temperature of
160°F (71°C) to 200°F (93°C) is reached.
2. Pull out the dipstick and wipe it with a clean
rag or paper towel.
3. Push it back in all the way, wait three seconds
and then pull it back out again. Repeat the
check procedure to verify the reading.
4. Safe operating level is within the
HOT RUN band on the dipstick. The width of
the HOT RUN band represents approximately
1.06 quart (1.0 liter) of uid at normal
operating temperature.
5. If the uid level is not within the
HOT RUN band, add or drain uid as
necessary to bring the uid level to within
3 the HOT RUN band.
6. If the uid level is in the acceptable range,
push the dipstick back in all the way.
How to Add Automatic Transmission
Fluid
Refer to the Maintenance Schedule to determine
what kind of transmission uid to use. See
Recommended Fluids and Lubricants on page 629.
Add uid only after checking the transmission uid
while it is hot. A cold check is used only as a
reference. If the uid level is low, add only enough
of the proper uid to bring the level up to the HOT
area for a hot check. It does not take much uid,
generally less than one pint (0.5 L). Do not overll.
Notice:Use of the incorrect automatic
transmission uid may damage your vehicle,
and the damages may not be covered by
your warranty. Always use the automatic
transmission uid listed inRecommended
Fluids and Lubricants on page 629.
After adding uid, recheck the uid level as
described under “How to Check Automatic
Transmission Fluid,” earlier in this section.
When the correct uid level is obtained, push
the dipstick back in all the way.
496

A cold uid 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 for ve minutes if
outside temperatures are 50°F (10°C) or more. If it
is colder than 50°F (10°C), you may have to idle
the engine longer. Should the uid level be
low during this cold check, you must check the
uid hot before adding uid. Checking the uid hot
will give you a more accurate reading of the
uid level.
Checking the Fluid Level
Prepare your vehicle as follows:
1. Park your vehicle on a level place. Keep the
engine running.
2. With the parking brake applied, place the shift
lever in PARK (P).
3. 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).
4. Let the engine run at idle for three minutes
or more.Then, without shutting off the engine, follow
these steps:
The transmission
dipstick handle with this
graphic is located at
the rear of the engine
compartment, on
the passenger’s side
of the vehicle.
SeeEngine Compartment Overview on page 480
for more 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.
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If No Steam Is Coming From Your
Engine
The ENGINE COOLANT HOT message, along
with a low coolant condition, can indicate a serious
problem.
If you get an engine overheat warning, but see or
hear no steam, the problem may not be too
serious. Sometimes the engine can get a little too
hot when you:
Climb a long hill on a hot day.
Stop after high-speed driving.
Idle for long periods in traffic.
Tow a trailer. SeeTowing a Trailer on
page 429.
If you get the ENGINE COOLANT HOT message
with no sign of steam, try this for a minute or so:
1. If your air conditioner is on, turn it off.
2. Turn on your heater to full hot at the highest
fan speed and open the windows as
necessary.
3. If you are in a traffic jam, shift to
NEUTRAL (N); otherwise, shift to the highest
gear while driving — DRIVE (D) or THIRD (3).If you no longer have the overheat warning, you
can drive. Just to be safe, drive slower for
about 10 minutes. If the warning does not come
back on, you can drive normally.
If the warning continues, pull over, stop, park, and
fast idle your vehicle right away.
If there is still no sign of steam and your vehicle
is equipped with an engine-driven cooling fan,
push down the accelerator until the engine speed
is about twice as fast as normal idle speed for
at least three minutes while you are parked.
If there is still no sign of steam and your vehicle is
equipped with an electric engine cooling fan, idle
the engine for three minutes while you are parked.
If you still have the warning, turn off the engine
and get everyone out of the vehicle until it
cools down. Also, see “Overheated Engine
Protection Operating Mode” later in this section.
You may decide not to lift the hood but to get
service help right away.
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Overheated Engine Protection
Operating Mode (V8 Engines Only)
If an overheated engine condition exists and
the REDUCED ENGINE POWER message
is displayed, an overheat protection mode which
alternates ring 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. SeeEngine Oil (Gasoline Engine) on
page 486.
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
8.1L V8 Engines
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Engine Fan Noise
If 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.If 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.
514

Front Turn Signal, Sidemarker and
Daytime Running Lamps
A. Sidemarker Lamp
B. Retainer Clip
C. Front Turn Signal Lamp
D. Daytime Running Lamp (DRL)To replace a front turn signal, sidemarker or DRL
bulb, do the following:
1. Open the hood. SeeHood Release on
page 479for more information.
2. Remove the headlamp assembly as described
previously. SeeHeadlamps on page 533for
more information.
3. Press the retainer clip (B), located behind the
turn signal assembly, towards the outside of
the vehicle.
4. Pull the turn signal assembly out of the
vehicle.
534

{CAUTION:
Rust or dirt on a wheel, or on the parts to
which it is fastened, can make wheel nuts
become loose after a time. The wheel
could come off and cause an accident.
When you change a wheel, remove any
rust or dirt from places where the wheel
attaches to the vehicle. In an emergency,
you can use a cloth or a paper towel to do
this; but be sure to use a scraper or wire
brush later, if needed, to get all the rust
or dirt off. SeeChanging a Flat Tire on
page 564.
When It Is Time for New Tires
One way to tell when it
is time for new tires is
to check the treadwear
indicators, which will
appear when your tires
have only 1/16 inch
(1.6 mm) or less of tread
remaining. Some
commercial truck tires
may not have treadwear
indicators.
555

CAUTION: (Continued)
Use another type of traction device
only if its manufacturer recommends
it for use on your vehicle and tire size
combination and road conditions. Follow
that manufacturer’s instructions. To help
avoid damage to your vehicle, drive
slowly, readjust or remove the device if it
is contacting your vehicle, and do not
spin your vehicle’s wheels.
If you do nd traction devices that will t,
install them on the rear tires.
Notice:If your vehicle does not have dual
wheels and is equipped with a tire size other
than P265/75R16, LT265/75R16, P265/70R17
or P275/55R20, use tire chains only where legal
and only when you must. Use chains that
are the proper size for your tires. Install them
on the tires of the rear axle. Don’t use
chains on the tires of the front axle.Tighten them as tightly as possible with the
ends securely fastened. Drive slowly and follow
the chain manufacturer’s instructions. If you
can hear the chains contacting your vehicle,
stop and retighten them. If the contact
continues, slow down until it stops. Driving
too fast or spinning the wheels with chains on
will damage your vehicle.
If a Tire Goes Flat
It is unusual for a tire to blowout while you are
driving, especially if you maintain your vehicle’s
tires properly. If air goes out of a tire, it is
much more likely to leak out slowly. But if you
should ever have a blowout, here are a few tips
about what to expect and what to do:
If a front tire fails, the at tire will create a drag
that pulls the vehicle toward that side. Take
your foot off the accelerator pedal and grip the
steering wheel rmly. Steer to maintain lane
position, and then gently brake to a stop well out
of the traffic lane.
563

4. Turn the wheel wrench (H) counterclockwise
to lower the spare tire to the ground. Continue
to turn the wheel wrench until the spare tire
can be pulled out from under the vehicle.
If the spare tire does not lower to the ground,
the secondary latch is engaged causing
the tire not to lower. SeeSecondary Latch
System on page 580.
5. Use the wheel
wrench hook which
allows you to
pull the hoist cable
towards you to
assist in reaching
the spare tire.6. Tilt the retainer (D)
at the end of the
cable (C) when the
tire has been
lowered, so it can
be pulled up through
the wheel opening.
7. Put the spare tire near the at tire.
570