12.7 detroit overheating and everything is new

Mine is new , alone with everything else .
S/S radiator tubes , Most everything is new from Grill to mudflaps
It doesn't seem to be boiling over , as my driver wont let it get over 225 and water boils at 212 plus pressure at 10lbs it would take 225 deg to boil .
I will try another new manual temp gauge but a diff brand , if that don't work I guess I'll take the head off and dig around

 

Yes from the last rebuild of original engine the fuel mileage went from 7 to 4.5 and barely 5.4ish after all the stuff been done and power never came back
(This engine used to impress me as a Detroit , with power and economy ) after this last rebuild ,bobtail it will only get 6.6 mpg , when before it would get better than 9 bobtail .
It was a $13,500. inframe by Clarke , remand head, turbo, and injectors .
That shop was going thru theft and a bunch of stuff about that time . afterward while I was trying to get the bugs worked out , they ended up getting rid of every single employee that worked there and thought I was involved in it till I showed receipts , but still have problems never solved and they don't care .
So she running hot and I'm changing the new manual Kenworth gauge out today to see what to do next .
Thank you all from input and opinions
I always had Detroit engines from 1989 till now , but I'm going with the RED HEAD engines from now on ..

 

No pyro , Temp gauge is same with ecm
, took the truck back to Clarke in Tupelo in hopes of finding something out ,
here is what I got
they worked all day riding around bobtail jamming to the stereo and when I got there and asked what did he find out
" your truck has lots of power and everything seems right on "
ok what about it running hot ?
Oh you have a radiator leak !! I asked where ? He showed me 3 drips in the floor where it had been sitting for a while as the engine was not hot at all and it 97 outside
I said OH YEA That is the reason its running hot
take the cap off every day and add maybe a quart every 3000 + miles
SO they hit me with a bill again and again nothing done .
So the gauge is right and I guess I can put 2 new 180 stats in and see how long before melt down and replace the engine with a crate engine ........