On a 1990-91 it is behind the housing the upper hose attaches to ON A 1.6 LITER
there is no 2.0l Pontiac lemans.it must be a swap from sunrunner.
diagram of timing belt
The marks are on the timing belt cover,and on the pulley for the crank.
its under the drivers side dase
The thermostat on a 2000 Pontiac Grand Am 2.4 liter 4 cylinder is located on the side of the engine. It can be found by following the upper radiator hose.
Raise or lower the temperature to change the reading on the thermostat.
information on how to change the themostat on a 94 Pontiac Grand am SE 2.3 liter
Try a engine reconditioning shop where they sell rebuilt engines, look in the yellow pages in your area.
In a 2.5L the handle end faces up.
Your question would be better answered if reposted including the year of your car.
Just follow the upper rad hose back to the top of the engine. Where it bolts in is where the thermostat is located.