1999 GMC C-SERIES Owners Manual

yellowblue
5-29 How to Add Coolant to the Coolant
Surge Tank
If you haven't found a problem yet, but the coolant level
isn't at the COLD ADD mark or higher, add a 50/50
mixture of clean, drinkable water and coolant at the
coolant surge tank, but be sure the cooling system,
including the coolant surge tank pressure cap, is cool
before you do it. (See the Caterpillar

Operation &
Maintenance Manual for the proper engine coolant to use.)
CAUTION:
Steam and scalding liquids from a hot cooling
system can blow out and burn you badly. They are
under pressure, and if you turn the coolant surge
tank pressure cap
-- even a little -- they can come
out at high speed. Never turn the cap when the
cooling system, including the coolant surge tank
pressure cap, is hot. Wait for the cooling system
and coolant surge tank pressure cap to cool if you
ever have to turn the pressure cap.
ProCarManuals.com

yellowblue
5-30
CAUTION:
Adding only plain water to your cooling system
can be dangerous. Plain water, or some other
liquid like 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 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.
ProCarManuals.com

yellowblue
5-31
1. 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 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 cap, but now push down as
you turn it. Remove the pressure cap.
ProCarManuals.com

yellowblue
5-32
3. Then fill the coolant surge tank with the proper
coolant mixture, up to the COLD FULL mark.
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 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 COLD FULL mark.
ProCarManuals.com

yellowblue
5-33
5. Then replace the pressure cap. Be sure the arrows on
the pressure cap line up like this.
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 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 when the clutch
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.
ProCarManuals.com

yellowblue
5-34
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 tells you what to do.
Changing a Flat Tire
A flat or damaged tire can be a major roadside problem.
You're very likely to have to go for help. Few drivers of
these vehicles have the necessary equipment aboard to
be able to change a flat tire safely. For example, youhave to have a truck jack that can lift several thousand
pounds and a torque wrench that can generate several
hundred foot
-pounds (newton-meters) of twisting force.
So if you're stopped somewhere by a flat or damaged
tire or wheel, you should get expert help right then.
If the correct equipment is available, though, here is the
procedure to follow.

Does the tire still seem to have air under pressure in
it? If so, stand to the side and look at the wheel. See
if it looks like another wheel on the vehicle. If so, go
on to the next step. If it doesn't, or even if you can't
be sure, stop and get expert help.
CAUTION:
Tire-rim assemblies can explode. If you work on
a pressurized tire mounted on a damaged wheel,
the assembly can expand with explosive force
without warning. You and others nearby can be
badly injured. Don't work around a tire that has
air under pressure in it when its wheel is or might
be damaged.
ProCarManuals.com

yellowblue
5-35

If the wheel looks normal, see if the wheel has side
rings and a lock ring around the wheel rim. If so,
they must be seated properly. You can compare with
another wheel on the vehicle as you check for this.
For dual wheels, you have to look between the tires
to make this check. You may not be able to tell
if the side rings or lock rings are seated properly
by looking. If you can't be sure, stop and get
expert help.
CAUTION:
If you work on a pressurized tire mounted on a
damaged wheel, the assembly can expand with
explosive force without warning. You and others
nearby can be badly injured. Don't work around
a tire that has air under pressure in it when its
lock ring or side ring might not be
properly seated.
CAUTION:
Rust or dirt on the wheel, or on the parts to
which it is fastened, can make the 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 the 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 you need to, to get all the rust or
dirt off.

If the lock ring and side rings seem to be seated
properly (or if the wheel doesn't have these), let the
air out of the tire. You can do this by taking out the
valve core.

If the flat or damaged tire is one of a dual set, let the
air out of both tires of the dual before you take off
the damaged tire and rim assembly.

If you have the correct equipment, put on the spare
wheel and tire assembly.
ProCarManuals.com

yellowblue
5-36
CAUTION:
Never use oil or grease on studs or nuts. If you
do, the nuts might come loose. Your wheel could
fall off, causing a serious accident.
CAUTION:

There are many ways to be hurt badly, or
be killed, while you are trying to change a
truck tire and rim. Follow all of the safety
precautions on the truck jack and
other equipment.
CAUTION: (Continued)
CAUTION: (Continued)

If you try to put air back into a tire that has
run flat, or even a tire that was quite low on
air, without first finding out why it was low
or flat, the tire can have a sudden air
-out.
This could cause you to lose control of the
vehicle and have a serious crash. Don't
refill a flat or very low tire with air without
first having the tire taken off the wheel and
checked for damage.

Use a clip-on chuck and hose extension when you
add air to your tires. You'll need an accurate truck
tire pressure gage. Stand to one side and add the air.
Be sure you don't go over the top inflation pressure
for the tire.
ProCarManuals.com