that's a good possibility. Let me know how that turns out.

if that doesnt solve the problem i suggest you check the water pump. look for any puddles that may be forming under your car. similar thing happened to me with the overheating and it was due to a bad water pump. i also kept getting low on coolant (all symptoms solved by getting the pump fixed)

yea the fact he said that he saw fluid over by the bleeder valve for the coolant system points at the water pump......easy to replace......and if they put a used engine in.......a probable cause......i was having cooling issues too......so i changed the thermostat to a lower degree one( i was in your position) after that i rarely ever saw above the 1/2 way mark.......then it started getting hot again.....was losing coolant thats when i noticed the drip below the pump, changed it, back to below or at 1/2 way.......since then i have had no problems besides upper hose blowing........upper radiator hose blown up = no fun lol........but yea check the pump, pretty easy to replace