GMC SIERRA 1997 Manual page 255

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.
How to Add Coolant to the Coolant
Recovery Tank
--
Gasoline Engines
If you haven't found a problem yet, but the coolant level
isn't at or above the COLD mark, add a 50/50 mixture of
clean water (preferably distilled) and DEX-COOL@
(silicate-free) antifreeze at the coolant recovery tank. (See
"Engine Coolant'' in the Index for more information.)
I
Adding only plain water to your cooling system
can be dangerous. Plain water, or some other
liquid like alcohol, can boil before the proper
coolant mix will. Your vehicle's coolant warning
system is set for the proper coolant mix.
CAUTION: (Continued)
With plain water or the wrong mix, your engine
could get too hot but you wouldn't get the
overheat warning. Your engine could catch fire
and you or others could be burned. Use a 50/50
mix of clean water and DEX-COOL@coolant.
I
NOTICE:
r
~~
In cold weather, water can freeze and crack the
engine, radiator, heater core and other parts.
Use the recommended coolant and the proper
coolant mix.
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