Chevrolet IMPALA 2005 Owner's Manual page 285

4. After the engine cools, open the coolant air bleed
valve or valves.
3400 V6 Bleed Valve #1
3400 V6 engine: There are two bleed valves. The first is
located on the thermostat housing. The second is
located on the thermostat bypass tube, on top of the
water pump housing.
3400 V6 Bleed Valve #2
3800 Series II V6 Bleed Valve
3800 V6 engine: There is one bleed valve. It is located
on the thermostat housing.
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