I know some stuff about cars. I've always worked on my own, but never had to deal with overheating. I bought a 2003 Chevy Impala 3.4L v6, transverse transaxle with 178,000 miles on it for $100. It had a misfire that a friend helped me fix (stripped head where a rocker arm bolted in - I put a helicoil in and it ran wonderfully.

Anyways... I flushed the coolant and put dexcool in but my friend says it has TWO air bleed valves on the coolant system. I can only find the front one, but once I flushed it, the engine stayed cool with no issues in 100° heat. Now it's still just as hot outside, but it overheats to about 70% of the guage and I gotta park and turn the heat on. 

I figured a lower temp thermostat would help and haven't tried it yet, but am I aiming in the right direction, here???