Engine/Transmission (1998.5 - 2002) Best temp T-stat ?

[LLewandowski]

New truck , On my stock gauge it reads just a tiny bit above half-way (the 140 - 190 mark) .



I'm sure these things arnt that accurate , but thats telling me 170-175ish ?(and thats after driving , at idel it won't budge) I want the hotest T-stat I can get , do you think I have a lower temp one in as of now?

 

[RustyJC]

On my 02, the stock 190 degF thermostat runs a needle width below the 190 mark when running empty and a needle width above the 190 mark when towing. It sounds like your thermostat may be hung partially open if your temps are that low.



Rusty

 

[TowPro]

I remember talking to the Cummins guy when I was buying a thermostat for my 98. he said "dodge is crazy for putting a 195 thermostat in that engine, it needs a 180".

 

[RustyJC]

Well, with all respect for the Cummins parts counter guy ( ), there are very valid thermodynamic and environmental reasons for running 190 versus 180 degree thermostats.



The point of my post was that the 2002 truck of the original poster was originally equipped with a 190 degF thermostat, and it appears to be malfunctioning.



Rusty

 

[BDanner]

4 season thermostat

I run with 2 thermostats. I change between a 180* for summer cooling and a 190* so as to stay warm in the winter. I used to freeze in the cab when OAT was in the 20's. Only 3 bolts to change out and an occasional gasket swap on the thermostat itself. I think the gasket is under $5.



The Cummins thermostats are more industrial quality in appearance than the aftermarket $30 Autozone model. I carry the replacement 180* Cummins thermostat in the truck just in case the 190* Autozone shoots craps.



Just a thought for you 4-season guys! Not practical for everyone.



Bruce in Northern Virginia

 

[Rattlin_Ram]

Bruce, you don't happen to have a part # for the cummins 180* t-stat do ya???

 

[BDanner]

Cummins 180* t-stat #

Try these. Found these numbers here on TDR in Geno's FAQ.





'98 & '99 '00+

Cummins 3935811 3954194 (180° )

3937171 (190°)









Bruce in Nothern Virginia

 

[Rattlin_Ram]

Thanks Bruce!!!

 

[CHolman]

Does anyone know where you can get a 180 degree t-stat for a 04?

 

[HookMeUp]

On a cold day, less than 25° my temp gauge will run up to the 190 mark and then fall back down to the 175 mark, then back up to the 190 mark and then, well you get the the idea. But if it's around 45° and higher it will stay at the 190 mark. What going on??

 

[KKlingbeil]

On a cold day, less than 25° my temp gauge will run up to the 190 mark and then fall back down to the 175 mark, then back up to the 190 mark and then, well you get the the idea. But if it's around 45° and higher it will stay at the 190 mark. What going on??

Mine does something kinna like yours... When its cold out, it will warm up, get to 190, go to about 200, then fall to like 180 or something, and then kinna go back and forth and even out at 190. i think i will try a new thermostat, the original has 108,000 miles on it...



Here's a good question: How long is a thermostat supposed to last???

 

[LLewandowski]

Well , looks like I'm going to get a new T-stat tomarrow .



I was asking the other day about fuel milage and why I wasn't geting over 16mpg , think an engine running too cold coould effect this?

 

[RAMICATOR]

On a cold day, less than 25° my temp gauge will run up to the 190 mark and then fall back down to the 175 mark, then back up to the 190 mark and then, well you get the the idea. But if it's around 45° and higher it will stay at the 190 mark. What going on??

i have notice this sometime also. i think because of the cold air temp at highway speeds, it cools the coolant a lot more than it would a say 75*, hence the drop of temp. IMO

 

[RustyJC]

I was asking the other day about fuel milage and why I wasn't geting over 16mpg , think an engine running too cold coould effect this?

Yep, although not a huge one. That's one of the thermodynamic considerations I mentioned.



Rusty

 

[LLewandowski]

Well I put the new t-stat in and its reading around 190 , if my mpg goes up I'll post the difference .





TY to everyone

 

[WestTN]

One more thing to consider. The stock fan clutch kicks in at 206. A cooler thermostat means more temperature swings in operation and therefore a little more wear.