Long story short. Let my 99 ES300 warm up about 15 minutes and everything seemed normal. I have a 45 mile commute and after about 30 miles I noticed my temp gauge hadn't moved from the cold position even though I still have heat. I believe it's the thermostat. Is this something I can replace myself? Any help/advice would be greatly appreciated.

Thanks!

 

The thermostat would cause on of two conditions, Either overheat, or not enough heat. If the guage never moved, it sounds like a temp sensor problem.

 

Is there anyway for me to check or should I just take it to the shop? Thanks for the help!

 

yeah, it does sound like a temp sensor problem. because even if you installed the thermostat with the jiggle valve upside down, the engine should warm up a little.
my .02
Charley

 

unplug the temp sender, Check the temp guage, then take a jumper wire and go from the sender plug(the wire connector), and touch it to ground somewhere on the engine, then check guage. If it moved, then the sending unit is bad.

 

Thanks! I will check it out tonight!

 

Or if you have a Digital Volt Meter, Check that there is continuity through the sensor. If so, its good. If not, its bad.

 

Thanks for all the help and it was the temp sending unit!!!