From a cold start, the first time it opens it will be just above what it runs normal. I don't know why but I've seen several trucks act this way. Mine opens at 186, but then runs at 180/183 all day long, unless I'm towing then it will go above that.
If you didn't figure it and before you ask, I run a 180 t-stat.arty018:

 

Ive noticed mine will hit 208 then drop to 197. Highest I have seen is 210 but then it dropped down to 197 again very quickly.

 

Mine is the same as yours, pops at around the 208 degree mark at first warm up, has done it since day one. Is this too high? Should I install a 190 degree thermostat?

 

Mine did the same thing. But after a while the first heat cycle would get higher and higher. It was to the point that I was seeing anywhere from 212 to 215 before the stat would open. I installed a 190* stat and all is well again. I would say its time to replace the stat.

 

I'm having the same issue. My T-Stat isn't opening until about 218* and stays between 203-205 constantly, it drives me crazy that my needle sits just past the 200* mark. Thinking its time for a new thermostat.

 

The thermostat is a coil spring (easiest way to explain it) that reacts to a certain pre-set temperature, 180, 190, 195 etc.. Our trucks come with a 190 degree from the factory. It opens/closes slowly to allow just enough coolant to pass to keep the engine at its rated thermostat temp. Normal operation would be in closed position until approx 204-210 degrees, then the thermostat opens as needed & holds its temp to 194-204, lower in colder outside weather and progressively hotter with heavy engine load or hot outside summer weather.

Your temperature is in the normal range. The 190 degree temperature is set to keep the engine burning its fuel "efficient" BUT mainly for the set EGR/emissions.

I have swapped my thermostat to a 180 degree (by stant) and temperatures rarely exceed 194-196 on a hot day. There are many disputes about this, but IMO the cooler coolant temperatures are better, especially pulling a heavy load in 95 degree summer days where keeping the engine cool is needed.

 

That's a very good explanation of how the thermostat plays part of the cooling equation. You're right, there's a huge debate between running the 180 and 190 in a diesel truck.
I actually noticed loss of mileage and longer warm ups with the 180 in my 05' and eventually went back to the 190 for year round. Our temps hit 125 on the asphalt and 115 ambient during our summers in Vegas. This 2010 seems to run much hotter. I'm going to try the 190, to see if I have a worn thermostat, and if that doesn't kick my temps down I'll try the 180.

 

I was a firm believer in running the 180* tstat, swapped back to stock temp one and I'll never put a 180* one back in. Cooler temp seemed to be the only pro, everything else you get is cons from it.

 

Would you care to share exactly what are the cons of running a 180* stat?? I have a 190* in mine and as far as I know have not had any troubles with it. But I also dont do a lot of towing(6k max).

 

So, the factory T-stat is 190 F?

 

That would be correct. We've covered that several times in this thread.

 

My factory one is a 200*.

 

I just changed mine yesterday . My trucks an 012 it had a 200 in it I replaced with a 190. Seems a lot better.

 

well i don't know how possible, but mine came with a 190 degree. so maybe cummins decided to change out thermostats through the years..? Factory thermostat from dealer for my truck is 190 & napa also states factory replacement is 190.

 

I'm new here but have a question. My son have an old 97 cummins that someone put bigger fuel plate in. Lots of them here in WY. Had the thermostate go bad so we put in a new one. The OLD one is a two stage thermostate. Has Mopar stamped on it. We are trying to find another one but no luck.
With the 2stage you warn up more evenly and run much more evenly. On these that is a big factor because of extra power and more heat under heavy load. Does anyone know where to get a 2stage thermostate??

 

You may want to post this in the 12 valve second gen section for more reply's
The old t-stats had 2 springs but I don't really think that they work any better then the single spring type :confused013:
They all have a wax plug that heats up and pushes against the spring to open up the valve.

 

To the OP. my truck has a 200* stock t-stat. Ive been running a 180* for over a year without a single issue. I tow about 16k. And my max temp is 185. Towing from Eugene to Coos Bay.

 

Hi Everyone,

I am new to the diesel engine realm and this change out of a thermostat has me curious and to be honest, I'm looking to be educated on why people change out their thermostat to a lower temp...

If the manufacturer has put in a 200 degree (which I believe mine has being a 2012) what is the real purpose of a cooler running temperature? I can understand longevity of running a cooler engine, but the manufacturer wouldn't just put a higher temp thermostat in for no reason....I would believe it is there for a purpose.
My main question is this: wouldn't a lower coolant temperature result in a lower overall engine temperature, creating more regens (for those of us who are stock configured) and lower gas mileage?

Thanks...