GMC Sierra 2000 Owner's Manual page 248

When the engine is cold, the coolant level should be at
or above the COLD mark. 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.
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.
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