Re: Bad thermostat?
Thermostats do NOT control max operating temp . . . I know this sounds like stupidity, but read this very carefully. Thermostats control MINIMUM temperature. By lowering the thermo number, you will not lower the max temp that an engine reaches under load unless the cooling system is already adequate to cool the engine. If the stat is fully open, it doesn't matter. Sooooooooo, what I am trying to say is if you have a 160 degree 'stat and you are running at an accurate 180 degrees then the cooling system is just barely able to keep up with it's job . 180 is probably a few degrees above the fully open temp of the 160 degree stat, so if a 140 degree stat would also be fully open, and the 160 degree stat is fully open, then you are probably technically, overheating. That definition being that the engine runs above the fully open temperature of the thermostat. That shouldn't happen.
Soooooooooo, you can check the stat, you can do all kinda things, but you need to know the accurate temp while under load (preferably at WOT which is max heat). This will tell you if you are exceeding the "range" capability of your stat which is usually around 15 degrees. If you are, then the stat is not your issue as long as it IS fully opening AND that it is not leaking i.e. bypassing when fully open which would let the hottest coolant back into the engine. So you need a good thermo, with a decent seal, against a good housing . . . But first you need to verify the operating temp. Your gauge is not the way to do this . . .
