Mine always hovers around the 190 mark also. Right below empty and right above towing.

 

All sounds understandable BUT...I can't buy the "cycling" thermostat concept though. Thermostats are not on/off switches with a lifespan measured in cycles. Thermostats constantly adjust from somewhere inbetween full open and full closed in a reasonably designed cooling system. I can't believe there's much "wear" going on while it's floating within the middle 80% of it's range. If anything, floating would cause spring fatigue resulting in a failed open as opposed to a failed close. VERY few stats fail open...they fail closed.

I also can't believe a constant 40* swing in coolant temp would be good for a motor.

RE: factory 20 psi...I do have to doubt they did that to make the motors last even longer. What would be the impetus to make a machine that never broke? It's prolly a variety of reasons.

 

I could be wrong, but when I have tested thermostats in a pan of boiling water, they most definitely had an "open" and a "closed" WITH NO IN BETWEEN. It was either open or it wasn't.

This was a while ago, so maybe the design is different now? Maybe they use a different design on the CTD?

Anyone know for sure?

Justin

 

That's because you couldn't vary and control the temp within a few degrees. If you could...you'd see it really has infinite positions.

 

Have seen a film on coolant that made reference to the variable positions of a thermostat - from fully closed to fully open and anywhere in between.

I hit the Hwy 2 mi from my house @ morning. Mine only fluctuates about twice from 190 down to 160 +/-, than climbs to 190 and stays there, as far as I can tell. This always made sense to me. Once the fluid (system wide) is heated up, the radiator does it's job and temps a stabilized, under most normal conditions.

Did I understand some of you get repeated major fluctuations - ongoing and all the time?
Rowland

 

My stuck thermostat repair is now in excess of $10,000.00.

 

On boats we have warning buzzers to warn of high temps. Sounds like cheap insurance to add. I'm sure the marine ones could be adapted easily.

 

Last I heard, the ISB's in the small OTR trucks used a 180. Is it possible that Dodge went to a 190 to get more heat in the cab? Or is it that Cummins runs the 180's so that the t-stat is more open to flow more fluid?


Something to think about.

 

Have to be careful regarding software, which could be diffferent in OTR.

In my wife's Mustang I put a 180 because they were out of 190. Caused all sorts of problems because the software had processes it went through when it got to 180. The 180 stat ran at 178 and these processes never/rarely got triggered.

 

I run a 180 in my 01 during the summer without problems. Switch to the 190 during the winter for more cab heat.