Buick 2001 Century Owner's Manual page 234

How to Add Coolant to the Radiator
NOTICE:
Your engine has a specific radiator fill procedure.
Failure to follow this procedure could cause your
engine to overheat and be severely damaged.
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.)
See "Engine Compartment
Overview" in the Index
for more information
on location.
If you hear a hiss, wait for that to stop. A hiss means
there is still some pressure left.
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.
2. Then keep turning the
pressure cap, but now
push down as you
turn it. Remove the
pressure cap.
5-17