GMC 1998 Safari Owner's Manual page 243

6. Start the engine and let it run until you can feel the
upper radiator hose getting hot. Watch out for the
engine cooling fan.
7. By
this time, the coolant level inside the radiator
filler neck may be lower. If the level is lower, add
more of the proper DEX-COOL@ coolant mixture
through the filler neck until the level reaches the
base of the filler neck.
8. Then replace the pressure cap. At any time
this procedure if coolant begins to flow out
filler neck, reinstall the pressure cap. Be su
arrows on the pressure cap line up like this
5-21