Thank you for asking this question
I have wondered the same in the past.
Before effecting a permanent fix by changing the fan clutch/fan on our 08 Journey with 350 Cummins 6.7L, I also experienced lights from overheating.
I never got to three different lights, however. It is my understanding that there is a sequence; 1st is high temperature warning, and 2nd is high temp STOP which throws a code. The first light alone does not leave a recordable code in the ECU. This is just my understanding, however, and may be incorrect.
As I moved uphill while driving, I could watch the temperatures rise. I understand that even as high as 210 degrees seems to me, that temperature is fine per Cummins. The light would come on at 215 degrees, and I pulled over.
At this point, I had the same questions as you, so I sort of split the difference. I was afraid to stop the engine completely and thus have no coolant flowing, so I allowed the engine to idle a few minutes. The light always went off after a short time - perhaps 90 seconds at idle. I then would shut the engine down after letting it run a bit more to cool off - which it always did while idling. I'm not sure if idling is the correct procedure, but I can say that the temperature always dropped consistently.
After walking the dogs or somesuch, I would crank the engine back up and proceed.
I did learn that if I geared down and let the engine run at 2100-2400 rpms (whatever gear was required to do this from 3rd or 4th), it would cool while running and I didn't have to stop etc., and the light wouldn't come on. The light typically came on when I didn't realize that we were heading up a grade or that cruise control was allowing the engine to lug and rpms to get down to 1500 or so (not an exact figure).
So - for future reference and barring something obvious like coolant spewing everywhere, in which case I would turn it off pronto....what IS the best practice?
Thank you for asking this question and helping my ongoing RV education. I'll keep an eye out for responses!
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John S
2008 Journey 39Z Cummins 350 ISB 6.7L
2006 Honda CR-V LX Tow
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