Buick 2001 Century Owner's Manual page 230

If the coolant inside the coolant recovery tank is boiling,
don't do anything else until it cools down.
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.
When the engine is
cold, the coolant level
should be at or above
the COLD mark on the
coolant recovery tank.
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.
See "Overheated Engine Protection Operating
Mode" in the Index.
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