First you have to see what the actual temp of the coolant is, if it's actually getting that high and the gauge reads correctly, then??

How does the temp sender look? Clean and tight? Battery connections clean and tight (I only say this because of grounding issues)? Maybe the gauge is just getting some intermitant signal from???

I'm not fimiliar with the Od's engine, but always check to make sure the electricals are working as they should. You may need a schematic to trace the signal from the sender to the gauge and see what it goes through like the ECU, cluster, dimmer switch, ground points etc, if anything.