Just inboard of the Water Pump, at the end of the Lower Radiator Hose, on the front passenger side of the engine...
The engine thermostat, on a 2008 Chevy Impala 3.5 V6, is located on the lower front side of the engine. The thermostat will have a water hose going into the top of it.
The 2008 Chevrolet Impala has a V6 engine.
The 2011 Chevrolet Impala has a V6 engine.
The 2001 Chevrolet Impala has a V6 engine.
The 2005 Chevrolet Impala has a V6 engine.
The 2013 Chevrolet Impala has a V6 engine.
The 2009 Chevrolet Impala has a V6 engine.
The 2004 Chevrolet Impala has a V6 engine.
The 2010 Chevrolet Impala has a V6 engine.
The 2007 Chevrolet Impala has a V6 engine.
The 2002 Chevrolet Impala has a V6 engine.
The 2006 Chevrolet Impala has a V6 engine.