GMC 2003 Sonoma Owner's Manual page 292

Checking Coolant
The coolant recovery tank is located in the engine
compartment near the passenger side of the vehicle.
See Engine Compatfment Overview on page 5-12
for more information on location.
The vehicle must be on a level surface. When your
engine is cold, the coolant level should be at ADD, or a
little higher. When your engine is warm, the level
should be up to FULL HOT, or a little higher.
Adding Coolant
If you need more coolant, add the proper DEX-COOL@
coolant mixture at the coolant remvery tmk.
Turning the radiator pressure cap when the
engine and radiator are hot can allow steam
and scalding liquids to blow out and burn you
badly. With the coolant recovery tank, you will
almost never have to add coolant at the
radiator. Never turn the radiator pressure
cap
--
even a little
--
when the engine and
radiator are hot.
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