Buick 1993 Roadmaster Owner's Manual page 224

How to Add Coolant to the Radiator
. .
i=
: .
i
i
i
t
. .
:
:.c,
-
, - ,
I.
.
I
-"
I
-c
2. Then keep turning the
pressure cap, but now
push down as
you
turn
it. Remove the.
pressure cap.
.
-..-
' .
. .
.
., 3. Fill the. radiator with
the proper mix, up to
the base of the filler
neck.
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 to the left 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.