There is no thermostat you have to by one at Auto Zone, Oriley's ect.
How do you Replace the thermostat in a 2005 grand prix gt
The thermostat is located near the intake on a 1999 Pontiac Grand Am GT. The thermostat can be located by following the upper radiator hose directly to the thermostat.
Can't give you an exact price, but i just replaced the thermostat in my eclipse gt and it was like $20 for parts, assuming you do the install.
Inside the thermostat housing, follow the upper rad hose back to the engine, under the throttle body.
the thermostat is right under your throttle body and it is difficult to get to
Under the thermostat housing
Follow the link below. This is how I removed the stereo on my 2000 grand prix gt
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Underneath the top radiator hose where is goes into the top of the engine.