Buick 1995 Century Owner's Manual page 188

3. Fill the radiator with the proper mix, up
to
the base
of the filler neck.
If you see a stream of coolant coming from
an
air
bleed valve, close the valve. Otherwise, close the
valves after the radiator is filled.
4. Rinse or wipe any spilled coolant from the engine
and compartment.
5. Then fill the coolant recovery tank
to the FULL
HOT mark.
5-22