GMC 2001 Sierra 1500 Pickup Owner's Manual page 319

NOTICE:
When adding coolant, it is important that you
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use only DEX COOL (silicate
If coolant other than DEX
the system, premature engine, heater core or
radiator corrosion may result. In addition, the
engine coolant will require change sooner
30,000 miles (50 000 km) or 24 months,
whichever occurs first. Damage caused by the
use of coolant other than DEX
covered by your new vehicle warranty.
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free) coolant.
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COOL is added to
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at
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COOL is not
If there seems to be no leak, start the engine again.
See if the engine cooling 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 Surge
Tank --Gasoline Engines
If you haven't found a problem yet, but the coolant level
isn't at or above the FILL COLD mark, add a 50/50
mixture of clean, drinkable water and DEX
coolant at the coolant surge tank, but be sure the cooling
system, including the coolant surge tank pressure cap, is
cool before you do it. See "Engine Coolant" in the Index
for more information.
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COOL
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