Chevrolet 1993 Astro Passenger Owner's Manual page 218

Problems on #he Road
How to Add Coolant to the Radiator
PO422
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
SOt-t~e
pressure left.
2.
Then keep turning the pressure cap, but now push down as you turn
it.
Remc- the pressure cap.
PO423
3.
Fill the radiator with the proper mix, up to the base of the filler neck,
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