check for blown head gasket.......block tester?.....
I did a compression test a few days ago and cylinders 1,2,4 were all 165. #3 was 160. So that seems ok from what I have heard.
only thing I can think of if it isn't the T-stat or a head gasket is that you have a bunch of sludge built up in the coolant passages in either your block or the head ( which is where most heat is created). If you still can't find the cause, throw an aluminum replacement radiator on it and be done.
I just installed a brand new 3row copper/brass v6 radiator with new coolant about a couple months ago. I replaced a perfectly good thick single row all aluminum radiator (one of the toyota 4x4 vendors sells it). I still have not installed a oem Toyota t-stat to replace the one I installed with the radiator. It's on my list of things to do when I get back in town.
