GMC 2008 Chevrolet Tahoe Supplemental Owner's Manual page 45

CAUTION:
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You can be burned if you spill coolant on hot
engine parts. Coolant contains ethylene glycol
and it will burn if the engine parts are hot
enough. Do not spill coolant on a hot engine.
If the DMCM coolant is empty, your vehicle must be
serviced by your dealer and a special fill procedure must
be followed.
Notice: Attempting to fill the DMCM cooling surge
tank yourself when the fluid level is empty can
damage your vehicle. Your vehicle must be serviced.
1. Park the vehicle on a level surface and turn the
vehicle off. You can remove the DMCM coolant
surge tank pressure cap when the DMCM cooling
system, including the DMCM coolant surge tank
pressure cap and DMCM cooling hoses, are no
longer hot. Turn the DMCM coolant surge tank
pressure cap slowly counterclockwise (left) about
one full turn. Wait 30 seconds.
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