Chevrolet 2007 Avalanche Owner's Manual page 474

How to Add Coolant to the Coolant
Surge Tank
If you have not found a problem yet, check to see if
coolant is visible in the surge tank. If coolant is
visible but the coolant level is not at or above the
FULL COLD mark, add a 50/50 mixture of clean,
drinkable water and DEX-COOL
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 on
page 465 for more information.
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coolant at the
If no coolant is visible in the surge tank, add
coolant as follows:
CAUTION:
{
Steam and scalding liquids from a hot
cooling system can blow out and burn
you badly. They are under pressure, and if
you turn the coolant surge tank pressure
cap — even a little — they can come out at
high speed. Never turn the cap when the
cooling system, including the coolant
surge tank pressure cap, is hot. Wait for
the cooling system and coolant surge
tank pressure cap to cool if you ever have
to turn the pressure cap.