Hi Rob,
I have an L2500 that is doing almost the same as yours was. I have pulled the radiator, flow checked it, pulled off the water pump, like new inside, replaced the thermostat, (the old one worked fine in pot of water on the stove) adjusted the fan belt, replaced the temp sending unit, shot all over the motor with a laser thermometer gun, getting readings around 210. Tractor has never over heated but keeps creaping closer to the red. It used to come right down below the 12 o'clock position at an idle, now it just goes hotter and hotter, never over heats but only goes down to about 1 o'clock when running at full load. never really cools down.
I read all of your posts and dont see that you came to a resolution to your trouble. Did you ever get it squared away? what did you find?
Please get back to me i am really at a loss on this and no one has had any advice that i have not tried yet, or have not already done. I dont want to just keep dumping money into this either! The new water pump that i did not need was more than enough unneeded expense
Thanks
Eric