Originally Posted by dieseldan2005
Temp sending unit maybe? The fuel gauges are iffy on almost all the super duties. I have seen those bad on 99's 03's 04's, etc... I would try and hook up a mobile scan tool to your ecm and monitor your coolant temp, just to make sure you don't have an issue with a bad egr cooler or head gaskets.
Thanks, I'll try scanning to see what results I get. Hopefully egr/cooler aren't bad, I replaced motor with another 6.0 w/ only 22,000 mile approx 15k ago. I think I'll need to invest in a monitor or gauge pod to watch everything just to be safe.