7580 Questions

I have been chisel plowing ground with my 7580 the past week.  I bought it to pull my grain buggy for last fall while I got time to get my 305 back together, which I am still working on, uhum, The 7580 on the grain buggy temperature gauge would run pretty much straight up and down.  I started it on the chisel plow and the gauge ran up almost to the red and I was about to quit then the gauge dropped down to the bottom line between straight up and down and the cold line and stayed there for the next day as well then he next day it went up to the red in a couple rounds and I stopped checked it with my temperature gun and the bottom of the thermostat housing was 215 degrees and upper rad hose was 174  lower rad hose was 127 degrees.  I put two new thermostats in it blew the radiator out again with the air gun and now it runs the needle straight up and down, that marking on the gauge says 210 degrees, however, when it was running cooler before I changed the  thermostats I was running a gear faster, now if I pull in that gear my temperature gauge runs higher than straight up and down closer to the red, but stays steady there.  I am thinking a recore of the radiator and rebuild the water pump as the bearing has  some play in it, pretty sure the rad is original as it has maroon paint and black over top of it .  

I'd say DrAllis nailed it.  Our 7580 gauge would show it getting hot when it wasn't working very hard.  We put a new Agco sending unit in it and that one would redline driving down the lane.  We put the old sending unit back in and added a manual gauge.  I never saw the manual gauge go over 180 while the original gauge moved back and forth from good to hot.  I thought the service manual actually warns technicians not to worry about the high readings unless it is blowing coolant and having to be topped off.

like every one says prove your gauge then move on to radiator compression if if cleaning the outside good and the mechanical gauge reads high