The other day the wife picked my truck up from inspection and said it smelled like coolant. I never had any issues before so I looked for leaks. Found none. Took it out and it seemed to take forever to get to 190 but it smelled like coolant before it got there telling me it was warm. The temp. (scan gauge and factory gauge) would go as high as 204 and then all of a sudden drop to 188 in a matter of 20 sec or so and then climb back up and repeat. What gets me is the radiator cap is cold even after a 1/2 hour drive and the bottom hose is cold but the top is hot so the stat must be opening. I thought the stat might have failed 1/2 open which would explain the symptoms so I put a new NAPA one in. Wanted a 190 but saw I got a 195 but put it in and now it won't go above 180. It's in the 30's out here but I thought the radiator should be getting warm. It's like the coolant isn't getting circulated but it never puked or seemed to get over hot. Is it possible the water pump isn't working right? Any other ideas? I'm looking at it all through a microscope now so to speak and I'm not sure whats normal. And just for my knowledge, the coolant flow is from motor through thermostat into top hose through radiator and back to the motor through the bottom hose right? It took me so long to get used to the reverse flow system in my LT1 that now I forget the which way is normal:banghead:. Also, I did a flush this summer and all looked good so I'm pretty sure I don't have any blocked passages.

I don't get the smell but the windshield fogs up all the time,it's a real pain. I wondered if the heater core was the cause but I usually can smell even minute amounts of coolant.

Heater core..............:banghead:

My napa 190 rides about 188, maybe 186 in the colder weather. If im cruising slower, then it runs closer to 180.

My Cummins 190° does the same. It was cold enough on my drive back from Seattle the other day that on shallow downhills I would run at 186° at 75 mph after running several hours. 180° seems to be the temp that it holds when fully closed at low load, such as idling, slow crawling, or coasting down a long hill. The swing is normal. The 190° thermostats crack at 190° ± 3°, and are not full open until 207°. Because of the over-sized cooling the radiator stays fairly cool/cold in the winter when your not towing so there is a rush of cold coolant into the block when the thermostat cracks, and it takes many mile of driving to stabilize the thermostat at the proper position to maintain temp, and then any power change will effect it. As the thermostats age they develop wear spots because they rarely go full open, in fact until I got my 8K lb TT my thermostat would only go full open a few times a year with my 4.5K lb TT, and that's with about 100rwhp over stock. The cooling system is WAY over-sized, and it's great. Anyways, the wear spots make them slower to react and reduce the ability to smoothly open. When I changed my OEM thermostat at 55K miles the difference was night and day. I went with a Cummins stat as I have heard of too many issues with non-Cummins ones. Anyways, as to running 180° on a 195° thermostat, how long had you been driving? I suppose it's possible that NAPA is rating the full open temp, not the crack temp like OEM does. The OEM 180° thermostat is full open at 198°.

My Cummins 190° does the same. It was cold enough on my drive back from Seattle the other day that on shallow downhills I would run at 186° at 75 mph after running several hours. 180° seems to be the temp that it holds when fully closed at low load, such as idling, slow crawling, or coasting down a long hill. The swing is normal. The 190° thermostats crack at 190° ± 3°, and are not full open until 207°. Because of the over-sized cooling the radiator stays fairly cool/cold in the winter when your not towing so there is a rush of cold coolant into the block when the thermostat cracks, and it takes many mile of driving to stabilize the thermostat at the proper position to maintain temp, and then any power change will effect it. As the thermostats age they develop wear spots because they rarely go full open, in fact until I got my 8K lb TT my thermostat would only go full open a few times a year with my 4.5K lb TT, and that's with about 100rwhp over stock. The cooling system is WAY over-sized, and it's great. Anyways, the wear spots make them slower to react and reduce the ability to smoothly open. When I changed my OEM thermostat at 55K miles the difference was night and day. I went with a Cummins stat as I have heard of too many issues with non-Cummins ones. Anyways, as to running 180° on a 195° thermostat, how long had you been driving? I suppose it's possible that NAPA is rating the full open temp, not the crack temp like OEM does. The OEM 180° thermostat is full open at 198°.

Thanks for the info. I drive mostly the same routes so I have a pretty good idea of what my temp should be at what location. Where it was normally at 190 I kept driving and 180ish was as hot as it got. The full open at 207 is great for me to know. Pulling my trailer the other day in some hilly terrain it would go to 207 and then fall off quickly to stabilize around 190. I guess I was just really lucky before with my Powerstroke and the stat I had in this truck. I've had it for 4 years now and it always was a steady 190. I might try a Cummins stat yet to see if I can get back to what I thought was normal. One things for sure. If I had circulation issues like I originally thought I would have melted it by now.