WOW, I think you found an issue with the belt. Who's belt and tensioner?

 

If the coolant looks rusty I would flush the whole thing with straight water untill it runs clean and refill with the correct stuff and see what happens. Mixing HOAT with other stuff causes wird problems.

 

dont be sorry it was a good idea, im just happy happy happy i dont have to worry about the transmission

 

for some reason my truck used to eat a belt to the point of snapping faster then i had to change the oil, after 10 belts it just flat out stopped doing it, and this belt is like 1.5years old and looks great, ever heard of this?

not sure, its the better belt from advanced and the tensioner might be MOPAR, it took 2 or 3 tensioners till they actually had a good one and ive returned like 10 belts that were for my truck and too dang big, i now make them pull 2 or 3 belts and check the lengths
i have a brand new belt hanging around and a tensioner is like 110 from advanced with lifetime warrenty but i dont want to chuck cash at it, on a whim but if i need it ill deffinalty get it

 

UpDate
just put on brand new temp sensor, and cleaned the intercooler and condensor something fierce, purple power and bugs b gone also check coolant for chunkies and there was nothing in the bucket when i drained a quart

last night the truck would not purge the air out of the system, it took about 24ounces and i drained more then that, so i ran it 50mph at 2800 rpms and drove the temp up to ~210 and it wouldnt go higher, and i checked it hot but the readiator was full, can the system purge itself and fill itself from the resivor? i filled it a bit last night at it was low after my run today

also i didnt see the head gasket bubbles while running it

the coolant looks fine maby a little rusty but its hard to tell since its red and ive added green, but i dont want to replace it all if i might have to drain it again,
i will be running 2 hour round trip on 95 tommarrow so i will be pushing 80-85 and see if it can keep cool

 

I would not attribute it to lack of airflow through the radiator. Mine has had most all the fins smashed in for years (thanks to my kids one day at ages like 2 and 5 thinking it was cool to smush them over!) and it does not run hot, even towing, up hill in 100deg temps.
Mixing the coolants will not turn anything to jello. HOAT is actually compatible with green coolant, green jsut has a much shorter service life.
(Not the same for OAT or Dexcool. It will turn cloudy if mixed with green.)

There is a good way to purge it by removing one of the little hoses to the head I believe. Sure it's written up on here somewhere, been a couple years since I changed the coolant on mine.

Maybe just the temp sensor was bad. Every time the temp would spike, did the fan kick in? You can hear it easily. If it's not kicking in, either it's not getting hot or the fan clutch isnt working right. COuld cause the temp to spike I suppose, but under normal conditions driving empty even in warm weather it should rarely kick on.
Dont put a lower temp t-stat in it. It's a false bandaid and diesels like to run at 200.
Belt sounds loose from your description, but every time I've had a loose serpentine belt on any engine, or a belt fouled with oil or something the belt squeals pretty good. If it's not squealing, then its probably not slipping.

Regarding eating belts, my 07 used to eat power steering pumps, unrelated, but what I've found is getting the right width and dia pulley is darn near impossible. Had to re-use the OE pulley every time and there is alot of confusion at the parts stores that show Cummins applications that are not correct. You may have had one of those mis matched pulleys (1 rib narrower)?

Don't know if any of this helps, but???

And once you get it sorted out for good, I'd flush it good and repalce with HOAT coolant. I dont think the mixed coolant is part of your problem now though.
Good luck

 

The purging trick and procedures for refilling the coolant is well described in the write-up on changing the water pump if ya need it...you disconnect the heater hose from the nipple back by #4 cylinder to purge the block..

Just out of curiosity, I tried running my truck at 2500 rpm last night on the way home, at 90mph I still couldn't get it to stay at 2500! ( that was about 2200)... whatcha doin there boy???

 

He tachs out quick with the G56 and 3.73 gears. 2300 rpm is around 70-75 mph. Same as I do with 48re and 4.10 gears.

 

2300 rpm with a g56 and 3.73?? ive got the same set up in an 06 and im only doing 2000 rpm at 70 mph almost sounds more like 4.10 ratio doesn't it?

 

rpms sound right. same as mine 70 = 2200 to 2300

 

Guys guys!! I was kidding! I am aware its a function of gearing.....
if I were loaded or had the OD off, I would be running up there too...
geesh......

 

driving a 6speed with true granny gears, 1st redlines at 7mph and if you dump the clutch the duallys hop, it sounds like you have a problem if you cant keep a steady rpm,
id really like a 2 speed rear end in so i could run high gears when im empty but that wont happen

 

thanks
the only fin damage is minor from boots when dummies stand on the bumper to work on it but i have a fin comb and i did actually straighten out a few bad spots (you can get a 7 sided coil fin comb from any AC supply shop for like $10 , it works OK

it couldnt have been a pulley because they werent changed when it stopped eating the belt

and you cant hear a belt squeak or the fan kick on over 2,000 rpms the truck roars for being stock

temp sensor did NOTHING, the air purged itself out, what ever was left in it
and when it runs cool at 90+mph ill consider changing the coolant, its on the list but i only want todo it once
i think its the belt and fan and wind force all together giving me fits

 

i think its the belt stretched or tensioner is going bad- heres why
i can turn 28-2900rpms in 4th (50-55mph) and it stays cool
and i can twist the belt 360 degrees and pull it back enough to take it off the pulleys with no wrench

so here my thought
i think at 75mph and 2400 rpms the belt is barely holding but still doing its job
but at 2500rpms and 80mph the force of the wind hitting the fan, increase of rpms and a slightly loose belt is letting the water pump slip Majorly (youll never hear the squeal unless its louder then a pig)

is this a possible cause?
and where should i get a new tensioner? Napa?
also temp sensor did nothing, the gauges does the same dance still

 

This is another situation where gauges would help diagnose the issue.

A pyro would tell you where your EGT's are when you are pushing the truck and it starts to get hot.
If the EGT's are too high, a boost gauge would tell you how your turbo is performing. Low boost at high loads would cause high EGT's which may be
causing the truck to run hot.

The factory in-dash water temp gauge is "real" unlike the oil pressure gauge but the sweep on it is very small.
My in-dash water temp gauge barely moves as the engine goes from 190F-220F.

I have an electric Autometer water temp gauge. Drilled and tapped the cast iron thermostat housing.
Since it is post thermostat, it tells me exactly when the thermostat opens and it's much more accurate than the factory in-dash gauge.