I just changed the thermostat, in hopes that was the cause of my Durango running cold. According to the gauge, it runs between 170-180. I put a 195 stat in, and the one I took out was also 195. I think the gauge is right and telling me it's not getting up to temp. The top radiator hose gets warm, but not as hot as I think It should. I can easily hold my hand on it. Could the coolant temp sensor be the culprit? I have no codes

 

go double check the box the new one came in. also it could have had the wrong stat in the box. or a mismarked stat at the factory. some free info. many years ago i read an artical from chrysler saying to drill a 1/8 hole in a stat. this lets air escape letting the coolant go through the system. this IS a chrysler approved mod. i have done this for decades. but only drill a 1/8 size more is NOT better.

 

The Box and stat said 195. And Im not following what the hole does. It lets coolant flow through, assuming the thermostat is closed?

 

The hole aids in burping air out of the system without the thermostat getting hot enough to open. I suppose it would also let a small amount of coolant to bypass the thermostat in the event that the thermostat failed to open but I don't think 1/8 inch is going to do a significant enough amount of cooling to make much of a difference.

 

It lets air flow through as well as a small amount of coolant. If you've got an air bubble trapped under the thermostat it won't let it (the thermostat) get warmed up to open, since air doesn't transfer heat nearly as well as water.

 

That makes sense. But I don't think I have an air bubble, because then at least it would warm up to where its supposed to be. Is there a chance my gauge is wrong, and my motor is up to temp and there is another reason why heater doesnt get warm like the heater core needs back flushed or something. I really think its the motor temp though, it just doesn't put off as much heat as I remember like when I open the hood.

 

I had that issue too. Did a new t-stat and lots of cardboard, still didn't help. Then one summer it started to overheat, put in a new fan clutch and viola all issues solved.

 

And I understand "feeling" the heat off the engine isn't exactly accurate. But the temp gauge agrees with me

 

That is true, the clutch could be making the fan move more air than it needs to.

 

See I thought about that. I replaced mine with a severe duty from autozone, which I later learned was a bad move. Even after driving for twenty minutes when it's cold out, it never completely shuts off, and I don't know if it's normal. And in warmer temps lt would take forever to come off full blast.