What temperature to have electric fan turn on??

[vdubnut62]

Why would the O rings fail? Don't they have 220 degree plus oil splashed on the back side anyway.?
Somebody correct me if I'm wrong, I haven't been into my changfoid to take a look see.
Ron.

[Henry W]

O-rings used on oil pickups are able to withstand high temperatures. I beleive most modern engine manufactures use Viton O-rings and seals. Viton o-rings can take much higher temperatures than Nitrile/Buna-N. Viton o-rings can handle up to 400 F. oil temperature while, Nitrile/Buna-N is only good up to 250 F.

http://www.rainierrubber.com/pdf/Viton-Selection-Guide.pdf

Henry

[mobile_bob]

the changfa cylinder orings can stand some pretty elevated temperatures
i had my s195 all the way up to 260F once with no repercussions

mine system normally runs between 205 and 215F, with a 195 tstat
the stat stays open and the electric fan maintains the temperature between
this range.

fwiw
bob g

[tinkerer]

Thanks for all the replies guys! I see that the general consensus is to have the sensor in the top hose. You guys probably have more experience in this than me, but, I do want to explain why I was thinking it should be in the lower hose. I was thinking that if it is in the bottom of the hose and the radiator is doing its job, then the fan wouldn't kick on. But, if it was in the top hose, it could cause the fan to kick on as the thermostat, if working properly, would keep the coolant very close to the fan on temp even though the radiator is cooling the coolant enough by the time it enters the lower hose. I would think that this would cause the fan to run more than it is needed and also cause peaks and drops in the engine coolant temp rather than a constant temperature. I would think that this would be harder on engine gaskets and such.  I have operated a Kubota RTV utility vehicle that has a small 3 cylinder Kubota diesel in it that has an electric fan. Its sensor is in the top of the thermostat housing and I've noticed that the temperature varies quite a bit from the time the fan kicks on and until it kicks off. I was thinking that if the sensor was in the lower hose it would eliminate this temperature variance? Maybe it would not?....Whats your guys opinions on that? The radiator I have is a 3row radiator for a Honda Civic. I see that the one surplus center is selling with their 2TNV-70's is only a 1 row. I think I should have plenty of radiator. Here is the link to the fan I have..
http://www.ebay.com/itm/HONDA-CIVIC-DEL-SOL-3-ROW-ALUMINUM-RADIATOR-12-FAN-CAP-/380363062386?pt=Motors_Car_Truck_Parts_Accessories&hash=item588f67bc72&vxp=mtr

Thanks!
Ben

[Carlb]

If you put it in the lower I would think you would want it to go on at about 140 degrees F or so.

[Tom Reed]

I understand your logic about using the lower hose. But there is a reason manufacturers to it the way they do. Lets imagine the scenario that the engine is warmed up and running a light load, then all of a sudden a big load comes on and the engine is now working at max hp. A slug of hot water will flow out of the engine, through the radiator and eventually the temp will raised enough that the fan kicks on. Now you've got a radiator full of hot water that will be going into the engine without being cooled and the engine might over heat. With the sensor in the top hose the fan will kick on and cool the hot water as it comes into the radiator. This will actually supply a more steady inlet temp to the motor.

If you want to minimize cycling set the fan to come on at 210 deg and size the fan to be just big enough to do the job at full load max ambient temp.

[tinkerer]

I understand your logic about using the lower hose. But there is a reason manufacturers to it the way they do. Lets imagine the scenario that the engine is warmed up and running a light load, then all of a sudden a big load comes on and the engine is now working at max hp. A slug of hot water will flow out of the engine, through the radiator and eventually the temp will raised enough that the fan kicks on. Now you've got a radiator full of hot water that will be going into the engine without being cooled and the engine might over heat. With the sensor in the top hose the fan will kick on and cool the hot water as it comes into the radiator. This will actually supply a more steady inlet temp to the motor.

If you want to minimize cycling set the fan to come on at 210 deg and size the fan to be just big enough to do the job at full load max ambient temp.

Tom, thanks for the explanation. That makes perfect sense. I had never thought of it that way. Now for my next question... Since the top radiator hose would be best for the sensor, my engine has two plugs that I could screw a sensor in. These plugs are just before the thermostat. Would this location work or should the sensor be after the thermostat?