Thermostat Change and Electric Fan Temps

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03-10-2021
780ripper

Thermostat Change and Electric Fan Temps

Hi Guys, I'm changing to a cooler (160F) thermostat and would like to know what temperature range to set my cooling fans to? I figured that a good range would be 170F on and 155F off, with about 45 sec run on time after the ignition is turned off. Any input is appreciated.
03-10-2021
trlrider

Quote:

Originally Posted by 780ripper

Hi Guys, I'm changing to a cooler (160F) thermostat and would like to know what temperature range to set my cooling fans to? I figured that a good range would be 170F on and 155F off, with about 45 sec run on time after the ignition is turned off. Any input is appreciated.

Out of curiosity, why are you going with such a low thermostat?
Most modern engines have been found to function better at 190 - 195. Just curious, always learning based on others experiences.
What is the engine/trans/chassis set-up?
03-10-2021
780ripper

Hi tlr, so several reasons for the thermostat change:

the engine oil, transmission oil and coolant are tied into the same radiator so everything then runs hot,
im running a cast iron big block which generates a ton of heat, this degrades the oil and kills bearings
any oil i put in looks vaporized when i change it and
i plan on towing my trailer with this truck so i want to try and run it as cool as possible.
03-10-2021
lionelhutz

175* on and 170* off might be a good start to test. The fans should cycle on and off when stopped at idle if everything is working correctly. Use 155* off and they'll always run.
03-10-2021
In-Tech

Also lowers the octane requirement :innocent2:
03-10-2021
LeMarky Dissod

Quote:

Originally Posted by 780ripper

Hi Guys, I'm changing to a cooler (160°f) thermostat and would like to know what temperature range to set my cooling fans to?
I figured that a good range would be 170°F on and 155°F off, with about 45sec run on time after the ignition is turned off. Any input is appreciated.

Those fan-on settings are too cold for any thermostat, even the 160°F thermostat. Once a thermostat opens it should not open and close chronically; it should open wide and stay wide open til the powertrain is done working.

Quote:

Originally Posted by 780ripper

several reasons for the thermostat change:

the engine oil, transmission oil and coolant are tied into the same radiator so everything then runs hot
im running a cast iron big block which generates a ton of heat, this degrades the oil and kills bearings
any oil i put in looks vaporized when i change it, and
i plan on towing my trailer with this truck so i want to try and run it as cool as possible.

160°F thermostats are fully closed below 160°F, and fully open by about 176°F.
If you want the fans CONSTANTLY on for some strange reason? Fan-OFF @ 160°F or less.

With a 160°F / 71°C thermostat:
Set the Fan-OFF @ 176°F / 80°C. Any lower and the thermostat will stutter.
Set the Fan-ON @ 185°F / 85°C. This might let the fans shut off while the vehicle is moving fast enough to do the fan's work for them (45MpH or more).

Be sure the radiator (and external ATF cooler if also equipped?) are getting as much airflow into them as possible so that the fans' work is made easier.
Check your baffling, and consider adding coroplast in choice spots if need be.
03-13-2021
780ripper

thank you to everyone who replied, all great info, i would also like to thank the ppl who examined and corrected my tune file I will test the fans soon,
03-16-2021
780ripper

new 160F thermostat is in, i drilled a small bypass hole in it and the truck runs great, way cooler than before, now i just have to re-flash the pcm with the new fan control temps
03-17-2021
trlrider

Quote:

Originally Posted by 780ripper

Hi tlr, so several reasons for the thermostat change:

the engine oil, transmission oil and coolant are tied into the same radiator so everything then runs hot,
im running a cast iron big block which generates a ton of heat, this degrades the oil and kills bearings
any oil i put in looks vaporized when i change it and
i plan on towing my trailer with this truck so i want to try and run it as cool as possible.

Roger that! I guess coming from a Racing Background we always set oil, trans, engine, etc up with separate coolers and not integrated. And yes, the big block makes allot of oil temp heat.
Good Luck on your quest!
03-17-2021
Fast355

Quote:

Originally Posted by LeMarky Dissod

Those fan-on settings are too cold for any thermostat, even the 160°F thermostat. Once a thermostat opens it should not open and close chronically; it should open wide and stay wide open til the powertrain is done working.160°F thermostats are fully closed below 160°F, and fully open by about 176°F.
If you want the fans CONSTANTLY on for some strange reason? Fan-OFF @ 160°F or less.

With a 160°F / 71°C thermostat:
Set the Fan-OFF @ 176°F / 80°C. Any lower and the thermostat will stutter.
Set the Fan-ON @ 185°F / 85°C. This might let the fans shut off while the vehicle is moving fast enough to do the fan's work for them (45MpH or more).

Be sure the radiator (and external ATF cooler if also equipped?) are getting as much airflow into them as possible so that the fans' work is made easier.
Check your baffling, and consider adding coroplast in choice spots if need be.

Too much of a temperature cycle when you stop for me. With a 170°F thermostat my low speed comes on at 178°F and I have it set to turn the fans off at 176°F. I keep the on/off settings close because once the water starts to cool off at the coolant temp sensor the fans have already run long enough. It tends to run within a few degrees of 180. Like 178-182°F.