Chevrolet 1993 Astro Passenger Owner's Manual page 215

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PO453
The coolant level should be at or above FULL. If it isn't, you may have a
leak in the radiator hoses, heater hoses, radiator, water pump or somewhere
else in the cooling system.
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CAUTION
How to Add Coolant to the Coolant Recovery Tank
If
you haven't found a problem yet, but the coolant level isn't at or above
FULL, add a 50/50 mixture of clean water (preferable distilled) and a proper
antifreeze at the coolant recovery tank. (See "Engine Coolant" in the Index
for more information about the proper coolant mix.)
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