Chevrolet 1995 Blazer Owner's Manual page 217

If the coolant inside the coolant recovery tank is boiling, don't
do anything
else until it cools down.
The coolant level should be at the ADD mark. 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.
NOTICE:
Engine damage from running your engine without coolant isn't
covered by your warranty.
If
there seems
to
be no leak, start the engine again. See if
the
fan speed
increases when idle speed is doubled by pushing the accelerator pedal down.
If it doesn't, your vehicle needs service. Turn off the engine.
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