Buick 2004 LeSabre Owner's Manual page 264

Radiator Pressure Cap If Steam Is Coming From Your Engine
Notice: The radiator cap on your vehicle is a
pressure-type cap and must be tightly installed to
prevent coolant loss and possible engine damage
from overheating. Be sure the arrows on the cap
line up with the overflow tube on the radiator
filler neck.
See Engine Compartment Overview on page 5-12 for
more information on location.
Engine Overheating
You will find a warning light about a hot engine as well
as an engine coolant temperature gage on your
vehicle's instrument panel cluster.
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