2nd temp sensor

[thepunisher]

I am doing the Jeep Cherokee fan install on my '72. I bought a second temp sensor switch to run with a relay. Where can I install the temp sensor? Is there a location on the passenger side of the block or the head just like the temp sensor on the drives side? I have some other options but I'd like to get a reading from the engine. This is a 350 GM crate motor with valve cover bolts on the edges.

[BCOWANWHEELS]

I couldnt get that fan to even cool my 6 cyl. Engine

[thepunisher]

Awesome, that's a confidence builder. I figured if the single fan wasn't moving enough air I would add a pusher fan in front of the radiator.

[mclairmo]

I though that most electric fans use a temp sensor probe that is inserted into the radiator. My Flex a Lite Black Magic has a bulb that merely touches the radiator fins and senses the temp in order to control when the fan turns on.

[Tx Firefighter]

There will be sensor holes on each head. The one on the right side will be plugged. Remove the plug and use that.

[hayhauler71]

You can buy an aftermarket fan switch from summit racing that threads into your engine block or intake manifold that is preset to turn your fan on at various temps and than shut off at various temps.

[Longhorn Man]

The fan doesn't cool the engine, it cools the rad.
you are better off getting the temperature reading from the rad.. upper drivers side, 3 or 4 inches from the top. That is the best place to put it.

[BCOWANWHEELS]

I prefer on the hot side of thermostat in the intake

[Longhorn Man]

you can prefer it, but it doesn't make it the best set up.

[thepunisher]

I wasn't comfortable with the stab through kind of temp sensor. I didn't feel like that was going to be the most robust setup. I want a temp sensor in the head to take a reading of how hot the coolant is in the engine. I wanted on at 180 degrees and off at 170. I already had a relay so I just bought a standard temperature switch from the local auto parts store.

[westofb]

Originally Posted by thepunisher

I wasn't comfortable with the stab through kind of temp sensor. I didn't feel like that was going to be the most robust setup. I want a temp sensor in the head to take a reading of how hot the coolant is in the engine. I wanted on at 180 degrees and off at 170. I already had a relay so I just bought a standard temperature switch from the local auto parts store.

I think with that set up your electric fan will run constantly once your truck reaches operating temp.

[mclairmo]

I think there is a very good reason why the aftermarket uses a probe that reads the temp off the radiator and not the engine. The radiator and engine temps will likely be different and when the fan should turn on is really dependant on the temp of the water in the radiator, not the engine.

[thepunisher]

I'm OK with the fan running constantly as long as the truck doesn't overheat. I am worried about this setup not being adequate to keep the engine cool enough though. I'm going to do an at home flush of the coolant. When I refill it I am going to add purple ice (first time I have tried this brand). I have used water wetter in the past and have had success with getting ~10 degrees of extra cooling. I'm looking for longevity in the motor so I want the engine to run below 200 degrees.

<addition>
Both types of aftermarket sensor kits are available. Flex-a-lite sells the radiator style, painless sells a sending unit style. I see this as personal preference. Once the thermostat is open and coolant is flowing through the entire coolant system why does it matter where the temperature is taken (honest question not a rhetorical statement)? The goal is to keep the engine at optimal operating temperature. I know the temperature of the coolant will vary throughout the system so where you take the temp will vary. But so what, as long as the coolant is getting cooled and in turn the engine what makes the radiator a better location for the temperature. Am I missing something?
<end addition>

[mclairmo]

IMO, you want the electric fan on as little as possible to prevent overcooling, to extend the life of the expensive fan motor and to prevent unnecessary stress on the charging system/alternator. The engine temp will usually be higher than the radiator temp, especially in the head. Putting the probe in the radiator will allow the fan to operate only when really needed. If your fan is not pulling enough cfm, though, then maybe you are correct and running it on all the time is best. In that case, forget the temp sensor/probe and run a toggle switch to the dash like a race car. You can then turn it on and off whenver you want based on what your temp gauge reads or just leave it on all the time.

[Longhorn Man]

if you are worried about max cooling, then why start with a sub par unit to begine with? A fan with a clutch is going to pull more air, and last. Usually when a clutch goes out, you have full time fan instead of NO fan like when a fan motor or relay or wires or sensor or even a fuse fails.
I've replaced many head gaskets due to a failed electric fan... not a single one due to a failed fan clutch.