Buick 1998 Century Owner's Manual page 282

Checking Coolant
When your engine is cold, the coolant level should be at
the COLD mark or a little higher. When your engine is
warm, the level should be up to the HOT mark or a
little higher.
If this light comes on, it
means you're low on
engine coolant.
Adding Coolant
If you need more coolant, add the proper DEX-COOL@
coolant mixture at the coolant recovery tank, but be
careful not to spill it.
If the coolant recovery tank is completely empty, add
coolant
to
the radiator. (See "Engine Overheating" in
the Index.)
6-22