Buick 2001 Regal 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.
5-16
See "Engine
Compartment
Overview" in the
Index for more
information
on location.
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.