Scratching head help detroit 60S 12.7

Ok so I'm scratching my head freightliner century truck has a new radiator new pump new fan clutch. When I start driving from zero, you know, hitting my gears to gain speed. It starts to overheat and can go up to 205 to 208. And then I gotta hit the fan clutch manually or It'll come down or if we get to 208 or even 2011 then th3 ecm decides to turn it on whenever it really wants to could be at 199 or 203 or 185 or 211. The computer turns on the fan clutch automatically. And it starts to come down when I'm going up hills even if I'm empty. It'll start overheating as well as it'll go up to like 209 210 and go down again. Should I replace the thermostat on the coolant temperature censor Or how can I test the water pump? I know it's new but it was from fleetpride also not the head I got my truck rebuilt going onto 80k miles already new everything

 

I have an ecm digital monitoring so gauge reads the same as digital

 

Yes it does

 

100% full all the time not wasting either

 

Going down the road on a hot day 195-200 at times stays 187-193 I'm not sure before truck would never go up 205 going up hill with 44k now it does