Saturday, November 1, 2014

This just in from Tom Bauer on Cummins Thermostats (Tuggers Vol.62)

I'd like to add a short post script to the thermostat article from the Fall Tuggers.   It's important to know that Cummins thermostats operate the exact opposite of a normal car engine thermostat. Opposite from a car thermostat, a Cummins thermostat CLOSES as the coolant get hotter. This only comes into play when you are attempting to remedy an overheating Cummins away from home port. If a car is overheating under normal conditions, it's usually assumed the thermostat is stuck closed. The "get home" remedy is to remove the thermostat. Your engine may just run cooler than normal. 
If you removed the thermostat from a normally operating Cummins, it would overheat!  I haven't tried it, but in theory, if you didn't have a replacement thermostat, and you were overheating because of a thermostat stuck open, you could force the thermostat closed (or block the passageway) and the engine should return to normal temperature. 
The coolant doesn't want to go through the heat exchanger due to the increased resistance to flow. The path of least resistance (straight back to the coolant pump) must be blocked (closed thermostat) for the coolant to go through the heat exchanger. 

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