I have searched for a bit now and have found a couple of different answers, everything from 165-210.
What is the best temp? I just flushed my system out and before I would never get above 180, and the fan seemed to always be going. Now it got above 210 for about 15 sec but sits just before the 210 mark. Mabey 200 but when I start driving about 15mph it falls way down to the 165 mark, then goes back up to 200ish when I am sitting at a stop light for more then a min.

Anyone?

 

sounds to me like you have a problem with your cooling system, likely some air in there.

the factory stat is a 190 F temperature, so 200-215 would be the 'normal' range(when the stat gets to 190 it allows the coolant to flow and it will then cool down closing the stat and the cycle will repeat until it stabilizes and you find a consistent temperature)

now if your temp gauge runs almost straight up that is perfectly acceptable for these trucks.

however your fluctuations seem extreme, your stat may be stuck open and your clutch could possibly be bad not allowing it to keep the temp down while stopped.

 

I just had the fan clutch replaced a couple hundred miles ago. I am gonna try and pull the therm and see if it is stuck open or not. Might as well considering how cheap and easy it is. Dont you just pull the top hose and scrape it out?

 

Here's where mine usually sits whether im moving or sitting. I replaced my fan clutch last summer also.

 

Mine sits in the exact same spot.

+1 shrp, I am thinking air or tstat

 

Well when I did my thermostat we had to take off the fan and unbolt the bracket so the a/c and alternator could move forward. Other wise the part of the housing that bolts down wouldn't clear it to come out.

 

Yeah my A/C and Alternator bracket had to come off to get it out. But I was doing the plenum gasket when I did mine, so it was the only logical thing to do.

 

Well if that is normal then I guess I am ok. It hasn't done it today. I think the system just needed to burp...

 

I'm Curious about that correct operating temp as well. I am concerned that the
engine is not entering open loop operations... or is it closed, I can't remember.
It seams that the MPG's could be better, and feel like it was better when it was
running hotter...

I have a 180 stat, and think sometimes that it should be closing down and
warming things up. When I bought the D it had a stuck closed 195... since I
replaced it with the 180, I really don't have a point of reference...

 

mine runs just (litteraly JUST, not even far enough for most people to notice) left of dead center (01+ dont have number son the gauge) so yours is running on the cold side , but thats bc of the 180* stat, this change is done by most people in order to improve performance slightly, this is done bc the engine runs colder as im sure you have noticed.