GMC 2007 Yukon XL Owner's Manual page 457

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
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 on page 449 for more information.
If no coolant is visible in the surge tank, add
coolant as follows:
{
Steam and scalding liquids from a hot
®
coolant at
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.
CAUTION:
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