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I have an 81 with 258 got it with an elec fan mounted inside radiator and a manual switch on dash. I would like to find the original fan and clutch if it had a clutch at a junk yard but need to know what it looks like, I also would like to keep the elec. fan and mount it outside rad, with a temp sensor switch...anyone know which switch is best and where to mount it in a water jacket without losing the temp gauge sender so I still have a temp gauge ???
Thanks for any replies.
Torqflo sells some controllers that come with a therm switch that you install between the radiator fins. You can adjust its settings, not sure what the min and max is. I would mount it at the intake of the water into the rad since that should give you the closest reading to engine temperature, which is what you are trying to control. Autozone sells them.

Any reason you are doing away with the electric as a main source of cooling?
Torqflo sells some controllers that come with a therm switch that you install between the radiator fins. You can adjust its settings, not sure what the min and max is. I would mount it at the intake of the water into the rad since that should give you the closest reading to engine temperature, which is what you are trying to control. Autozone sells them.

Any reason you are doing away with the electric as a main source of cooling?

Actually you are trying to control the temp of the water flowing back into the engine, so put the temp switch near the output of the radiator.

The job of the engine thermostat is to keep the engine at the proper temp (note I didn't say "keep the engine cool", because with today's modern emissions systems you must also keep the engine hot enough for proper combustion), and the job of the radiator and fan is to keep the coolant flowing back into the engine at a temp sufficient to let the engine thermostat do its job.

Example: if it is zero degrees outside, the coolant will lose a lot of heat just flowing through the radiator, and you may not even need to run the fan. If the temp switch is monitoring the temp of the coolant entering the radiator, it will turn on even though the coolant would get cooled enough just from the outside temp being so low and without the fan running.

With the switch is near the output, you're sending the right temperature coolant back into the engine with appropriate use of the fan - the fan will run much less on cold days because the radiator does the job without requiring the extra air flow from the fan.

This is also the reason radiator probe temp switches are better for electric fans than engine block temp switches.

Jeff
Actually you are trying to control the temp of the water flowing back into the engine, so put the temp switch near the output of the radiator.

The job of the engine thermostat is to keep the engine at the proper temp (note I didn't say "keep the engine cool", because with today's modern emissions systems you must also keep the engine hot enough for proper combustion), and the job of the radiator and fan is to keep the coolant flowing back into the engine at a temp sufficient to let the engine thermostat do its job.

Example: if it is zero degrees outside, the coolant will lose a lot of heat just flowing through the radiator, and you may not even need to run the fan. If the temp switch is monitoring the temp of the coolant entering the radiator, it will turn on even though the coolant would get cooled enough just from the outside temp being so low and without the fan running.

With the switch is near the output, you're sending the right temperature coolant back into the engine with appropriate use of the fan - the fan will run much less on cold days because the radiator does the job without requiring the extra air flow from the fan.

This is also the reason radiator probe temp switches are better for electric fans than engine block temp switches.

Jeff

Hmm - Never looked at it that way, good point - Guess I need to go move my temp switch! It's always something :)
YOUR QUESTION....
Any reason you are doing away with the electric as a main source of cooling?

I don't want to constantaly monitor temp gauge so I can manually switch fan on. Also don't know how accurate the old temp gauge in the speedo housing is.

I forgot about the radiator type probes I had one before on another vehicle.

Actually I wanted to have both mechanical fan and electric, I am in an area where there are triple digit temps in the summer an thats when I go into the desert and the hills most to prospect. So having 2 options for cooling is a benefit. :thumbsup:
I have to disagree about putting the temp switch near the output of the radiator, because if you do that then your actually running hotter than it reads, because the temp goes up as the coolant flows through the motor, so if your reading 210 down there, it could be 230+ in the head, in which case your overheating and don't even know it.
I have to disagree about putting the temp switch near the output of the radiator, because if you do that then your actually running hotter than it reads, because the temp goes up as the coolant flows through the motor, so if your reading 210 down there, it could be 230+ in the head, in which case your overheating and don't even know it.

No, that's not what happens, I guess I should have provided more information in my post.

Typically the radiator probe is set to a lower temp than the engine thermostat. So if you've got a 195 degree thermostat, you might have your radiator probe set at 180. That way you are always returning 180 degree water to the engine.

If it is cold out and the radiator can cool the coolant to 180 by itself, the fan won't run. In warmer weather the fans runs as necessary to keep the coolant leaving the radiator to 180.

And if overheating happens you would know it because the temp gauge on the dash is still reading the temp in the head, not the temp at the radiator probe.

I've got the 195/180 combo in my CJ and the temperature as reported by both my dash temperature gauge and my EFI computer is very steady at about 205, which is the correct operating temp with a 195 thermostat. These cold days in the winter the only time the fan really runs is if I'm sitting in traffic and there isn't any air flowing through the radiator due to lack of movement of the Jeep. As soon as I start moving the fan will slow down and stop.

I hope this clarifies things.
Jeff