Engine/Transmission (1994 - 1998) 1997 Thermostat Fluctuations

[rknichols]

I've followed the THERMOSTAT issue on the 97's for some time. I've had a Cummins and a MOPAR and both have fluctuated up and down. Before leaving Michigan and heading to Florida this week I changed anti-freeze so decided to put on new hoses and try a NAPA thermostat as I've read some threads that it works the best. It fluctuated from 140 to 190 until the outside temperature hit 70, then it stopped and remained on 180 the rest of the trip. I was pulling about 6000# of trailer. I'm interested to see what it does tomorrow when I unhook and drive empty again. It is bothersome to watch it go up and down. Always checking to see if it keeps climbing.

 

[y-knot]

They are known to stick, just hope it doesn't stick closed. They do make "fail-safe" thermostates, but I don't know if they make them for a cummins.