1999 GMC YUKON Owner's Manual

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5-15 How to Add Coolant to the Radiator
1. You can remove the radiator pressure cap when the
cooling system, including the radiator pressure cap
and upper radiator hose, is no longer hot. Turn the
pressure cap slowly counterclockwise until it first
stops. (Don't press down while turning the
pressure cap.)
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, but now push
down as you turn it. Remove the pressure cap.

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5-16
3. Fill the radiator with the proper DEX-COOL

coolant mixture, up to the base of the filler neck.
(See ªEngine Coolantº in the Index for more
information about the proper coolant mixture.)
4. Then fill the coolant recovery tank to the
COLD mark.
5. Put the cap back on the coolant recovery tank, but
leave the radiator pressure cap off.

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5-17
6. Start the engine and let it run until you can feel the
upper radiator hose getting hot. Watch out for the
engine cooling fan.
7. By this time, the coolant level inside the radiator
filler neck may be lower. If the level is lower, add
more of the proper DEX
-COOL
coolant mixture
through the filler neck until the level reaches the
base of the filler neck.
8. Then replace the pressure cap. At any time during
this procedure if coolant begins to flow out of the
filler neck, reinstall the pressure cap. Be sure the
arrows on the pressure cap line up like this.

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5-18
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 disengages.
If a Tire Goes Flat
It's unusual for a tire to ªblow outº while you're driving,
especially if you maintain your tires properly. If air goes
out of a tire, it's much more likely to leak out slowly.
But if you should ever have a ªblowout,º here are a few
tips about what to expect and what to do:
If a front tire fails, the flat tire will create a drag that
pulls the vehicle toward that side. Take your foot off the
accelerator pedal and grip the steering wheel firmly.
Steer to maintain lane position, and then gently brake to
a stop well out of the traffic lane.
A rear blowout, particularly on a curve, acts much like a
skid and may require the same correction you'd use in a
skid. In any rear blowout, remove your foot from the
accelerator pedal. Get the vehicle under control by
steering the way you want the vehicle to go. It may be
very bumpy and noisy, but you can still steer. Gently
brake to a stop
-- well off the road if possible.
If a tire goes flat, the next part shows how to use your
jacking equipment to change a flat tire safely.

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5-19
Changing a Flat Tire
If a tire goes flat, avoid further tire and wheel damage
by driving slowly to a level place. Turn on your hazard
warning flashers.
CAUTION:
Changing a tire can cause an injury. The vehicle
can slip off the jack and roll over you or other
people. You and they could be badly injured.
Find a level place to change your tire. To help
prevent the vehicle from moving:
1. Set the parking brake firmly.
2. Put the shift lever in PARK (P).
3. If you have a four
-wheel-drive vehicle,
be sure the transfer case is in a drive
gear
-- not in NEUTRAL (N).
4. Turn off the engine.
To be even more certain the vehicle won't move,
you can put blocks at the front and rear of the
tire farthest away from the one being changed.
That would be the tire on the other side of the
vehicle, at the opposite end.
The following steps will tell you how to use the jack and
change a tire.

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5-20 Removing the Spare Tire and Tools
The equipment you'll need is located in the rear cargo
area. The spare tire is located under the rear of
the vehicle.To open the jack cover, turn the wing nut
counterclockwise and take the cover off.
To take the jack out, turn the wing
-head bolt
counterclockwise and take it and the retainer off. Take
the jack and storage box out and take the tools out of
the box.
Your vehicle may have a pair of emergency gloves
secured to the jack. You can use them when changing
the tire, or during other emergency situations.
Remember to replace them with the jack, so you will
have them if needed later.
The spare tire is stored under the vehicle in an
underbody carrier.

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5-21
A. Hoist Assembly
B. Hoist Shaft
C. Ratchet
D. Jack HandleE. Retainer
F. Valve Stem,
Pointed Down
G. Spare TireFollow these instructions to lower the spare tire:
1. One side of the ratchet has an UP marking. The other
side has a DOWN marking. Assemble the ratchet
to the hook near the end of the jack handle
(as illustrated) with the DOWN marking facing
you. Insert the other end through the hole in the
rear bumper and into the hoist shaft.
2. Turn the ratchet counterclockwise to lower the spare
tire to the ground. Continue to turn the ratchet
until the spare tire can be pulled out from under
the vehicle.
3. When the tire has been lowered, tilt the retainer at
the end of the cable so it can be pulled up through
the wheel opening.
4. Put the spare tire near the flat tire.

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5-22
The tools you'll be using include the jack (A), the jack
handle extension (B), the jack handle (C), the wheel
wrench (D) and the ratchet (E).
The jack handle extension is used if the flat tire is on the
rear of the vehicle.Attach the jack handle (and jack handle extension, if
needed) to the jack.