1999 GMC C-SERIES engine coolant

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5-21
CAUTION:
If your vehicle has air conditioning, the auxiliary
electric engine cooling fan under the hood can
start up even when the engine is not running and
can injure you. Keep hands, clothing and tools
away from any underhood electric fan.
If the coolant inside the coolant recovery tank is boiling,
don't do anything else until it cools down.
Specialty Hood
The coolant level
should be above the
HOT LEVEL mark on the
vehicle with the specialty
hood, or at or above the
COLD LEVEL mark
on the vehicle with the
sloped hood.
Sloped Hood
If it isn't, you may have a leak in the radiator hoses,
heater hoses, radiator, water pump or somewhere else in
the cooling system.
CAUTION:
Heater and radiator hoses, and other engine
parts, can be very hot. Don't touch them. If you
do, you can be burned.
CAUTION: (Continued)
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5-22
CAUTION: (Continued)
Don't run the engine if there is a leak. If you run
the engine, it could lose all coolant. That could
cause an engine fire, and you could be burned.
Get any leak fixed before you drive the vehicle.
NOTICE:
Engine damage from running your engine
without coolant isn't covered by your warranty.
NOTICE:
When adding coolant, it is important that you use
only DEX
-COOL
(silicate-free) coolant.
NOTICE: (Continued)
NOTICE: (Continued)
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 occurs first. Damage caused by the use
of coolant other than DEX
-COOL
is not
covered by your new vehicle warranty.
If there seems to be no leak, start the engine again. See if
the engine cooling fan speed increases when idle speed is
doubled by pushing the accelerator pedal down. If it
doesn't, your vehicle needs service. Turn off the engine.
How to Add Coolant to the Coolant
Recovery Tank
If you haven't found a problem yet, but the coolant level
isn't at or above the HOT LEVEL mark on the vehicle
with the specialty hood, or at or above the COLD LEVEL
mark on the vehicle with the sloped hood, add a 50/50
mixture of clean, drinkable water and DEX
-COOL

engine coolant at the coolant recovery tank. (See ªEngine
Coolantº in the Index for more information.)
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5-23
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 DEX
-COOL
coolant.
NOTICE:
In cold weather, water can freeze and crack the
engine, radiator, heater core and other parts.
Use the recommended coolant and the proper
coolant mixture.
Specialty Hood Sloped Hood
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.
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5-25 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.
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.)
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5-26
4. Then fill the coolant recovery tank to the HOT
LEVEL mark on the vehicle with the specialty hood,
or approximately one
-half full on the vehicle with
the sloped hood.
5. Put the cap back on the coolant recovery tank, but
leave the radiator pressure cap off.
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(s).
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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5-27
Cooling System (Diesel Engine)
When you decide it's safe to lift the hood, here's what
you'll see:
Caterpillar
Diesel Engine
A. Engine Fan
B. Coolant Surge Tank
CAUTION:
If your vehicle has air conditioning, the auxiliary
electric engine cooling fan under the hood can
start up even when the engine is not running and
can injure you. Keep hands, clothing and tools
away from any underhood electric fan.
If the coolant inside the coolant surge tank is boiling,
don't do anything else until it cools down.
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5-28
The coolant level
should be at COLD
ADD or higher. If it
isn't, you may have a
leak in the radiator
hoses, heater hoses,
radiator, water pump
or somewhere else in
the cooling system.
Caterpillar

Diesel
Engine
CAUTION:
Heater and radiator hoses, and other engine
parts, can be very hot. Don't touch them. If you
do, you can be burned.
Don't run the engine if there is a leak. If you run
the engine, it could lose all coolant. That could
cause an engine fire, and you could be burned.
Get any leak fixed before you drive the vehicle.
NOTICE:
Engine damage from running your engine
without coolant isn't covered by your warranty.
If there seems to be no leak, start the engine again. See
if the fan speed increases when idle speed is doubled by
pushing the accelerator pedal down. If it doesn't, your
vehicle needs service. Turn off the engine.
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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.
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