I understand that the engine cooling thermostat is designed to guarantee a minimum engine temperature of 192 to 199F. My van has the digital readout that displays the engine coolant temperature. With an ambient of 8F the readout stabilizes between 174 and 177F (>15 miles at 60 mph). If I set the internal heating fans to high I can pull the temperature under 170F. My dealer runs it in the shop and says the system is operating normal. The temperature does go up to about 200F when driving slow in town or idling in the shop. With an ambient of 40F the temperature at 60 mph stabilizes between 181 and 185F. I believe that the thermostat never fully closes. The wax driven reverse poppet choke thermostat is supposed to provide the fastest warm up possible, this vehicle has by far the slowest warmup of the four vehicles I own (including my old van). What are your thoughts?

 

My car has a 2.8CRD Diesel and its target operating temperature is 80C or 176F so it seems to me that the temperature is there and close to right, unless it is supposed to be so much hotter. If the thermostat was stuck even partially open the hose from thermostat to radiator would warm up as the engine warms up - it should stay cold until the enging is warm enough to open the thermostat. I have a stuck open thermostat on my Grand Voyager (Town & Country) and to prove it to myself I did just as described above.

I dont know if it is your problem, for example it could be a water pump problem too I suppose, but it does seem a good bet. Open the hood and monitor the radiator hose temperature first thing on a cold morning and see what you think

vrm8883

 

Pentastar111, your symptoms re. engine heating up in cold weather are identical with my 2.7ltr. diesel Jaguar -- i.e. turning on the heater dropped the engine temperature immediately.
Diesels don't make much spare heat in the coolant (that's why they are so fuel efficient) and you notice it in terms of a long warm up time in winter, and that effect from the heater you mention.
I could make the Jag. warm up a little faster by blocking most of the freezing air flow into the engine bay, then you need a good memory to remove the blockage when it gets warmer. Your digital display of coolant temp. is very handy here.

Leedsman.

 

On previous vans it's a cheap and easy replacement. If that's still true on the 12s go for it. It will ease the mind.

 

Hi Pentastar111

I saw your post from 2013 and in the year 2020, I am having same problem as you. I hope you see this reply..
My minivan is 2013 Dodge Grand caravan and having exact same issue. When ambient is <25F my engine (coolant temp) stabilizes 176-179 on high way, Ambient tmep ~40F the engine temp stabilizes 180-185 on highway. On street drving regardless of ambient temp, the engine is 195F. I have rand new Thermostat and still having the issue. Did you ever figure out what was your problem? Thanks.