Hummer 2006 H2 - Manual (Page 360)

If there seems to be no leak, start the engine again.
The engine cooling fan speed should increase when idle
speed is doubled by pushing the accelerator pedal
down. If it does not, your vehicle needs service. Turn off
the engine.
Notice: Engine damage from running your engine
without coolant is not covered by your warranty. See
Overheated Engine Protection Operating Mode on
page 5-28 for information on driving to a safe place
in an emergency.
Notice: Using coolant other than DEX-COOL ® may
cause premature engine, heater core or radiator
corrosion. In addition, the engine coolant may
require changing sooner, at 30,000 miles (50 000 km)
or 24 months, whichever occurs first. Any repairs
would not be covered by your warranty. Always use
DEX-COOL
® (silicate-free) coolant in your vehicle.
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 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 on page 5-24 for more information.
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 radiator
pressure cap — even a little — they can come
out at high speed. Never turn the cap when the
cooling system, including the radiator pressure
cap, is hot. Wait for the cooling system and
radiator pressure cap to cool if you ever have
to turn the pressure cap.
5-30