Electric fan thermostatic switch location; radiator or intake?

[derotoreut]

I am trying to figure out where is the best place to install my dual electric fan thermostatic switch. Should the switch be installed into the radiator or the intake manifold? I have the capability to install it in either location. My aluminum radiator (from Wizard Cooling) came with a welded coupling, which would allow me to install it into the radiator. Or is it best to be located at the intake manifold?

FYI I have a 383 stroker putting out 465 HP. Currently I have the thermostatic fan switch installed in the welded bung on the radiator, but I don't know if this is the best location. I did this so I could install the temperature gauge sender at the intake manifold (because there is no location on the block for it). Please chime in on this too, because this may not be the best location for a gauge sender.

I am running dual SPAL 13" fans with relays off of the single thermostatic switch. I also have a trinary switch installed in my Vintage Air AC system to control the fans. Thanks for your help.

[hayhauler71]

In the radiator at the upper hose would be the best spot as the coolant leaves the thermostat that is where I mounted mine

[Classic Heartbeat]

The probe for the thermostat should be placed in the radiator. The fans are cooling the water in the radiator, not the engine. WES

[Andy4639]

Originally Posted by Classic Heartbeat

The probe for the thermostat should be placed in the radiator. The fans are cooling the water in the radiator, not the engine. WES

Couldn't have said better!

[piecesparts]

Originally Posted by Classic Heartbeat

The probe for the thermostat should be placed in the radiator. The fans are cooling the water in the radiator, not the engine. WES

Actually I would think that you would want to know what your engine is at for temperature and not the radiator. I have installed several fan switches and all of them were triggered by a sensor in the intake manifold. I feel that the best thing is to put one in and adjust it to keep your engine at a set temperature. There are some aftermarket systems that do have a connection that uses a probe that sticks into the radiator fins, or into the return hose from the T/stat, but if you want a direct and functional connection, I would seriously consider a mounting point in the intake manifold. Putting the temp probe in the head does result in false temps due to combustion heat.

I spent a lot of money on my engine and I put in an aftermarket radiator and dual electric fans to keep it cool. The design of the fan switch is up to the buyer, but you definitely want one to work when you need it. Cooling an engine that is cooled by water is to move the right amount of air across a finned coil that has the water in it to supprt effective heat transfer. Actually an electric fan is better than many engine driven fans for a couple reasons. The first being that the fan continues to run at the speed that it was turning at 60 MPH with the car at dead stop, thus assisting in cooling the engine faster. Also the removal of the fan from the engine provides for approximately 10 hp more power to be used in the tranmission and this gains a little gas mileage. Finally, COLD weather, the lack of a fan turning on a cold morning, will allow the engine to heat up to temp faster.

My fan switch has a dual fan speed capability which turns the first fan on at a speed only necessary to keep the temp at the point that I set it for. If the temps goes up, the fan switch increases the fan's speed and then if really hot, the second fan is started to assist. I have yet to see the second fan run.

Both trucks in the attached pictures have aftermarket SPAL fan sets. The white truck has the fans behind the factory radiator and I used that truck for daily work (summer and winter driving), the black truck has a 400+ hp stroker engine behind the SPAL fans and an aluminum radiator that has been all over the country in more than one Hot Rod Power tour. I am happy to say they have supported me well.

[derotoreut]

Originally Posted by piecesparts

Actually I would think that you would want to know what your engine is at for temperature and not the radiator. I have installed several fan switches and all of them were triggered by a sensor in the intake manifold. I feel that the best thing is to put one in and adjust it to keep your engine at a set temperature. There are some aftermarket systems that do have a connection that uses a probe that sticks into the radiator fins, or into the return hose from the T/stat, but if you want a direct and functional connection, I would seriously consider a mounting point in the intake manifold. Putting the temp probe in the head does result in false temps due to combustion heat.

I would consider it, but I don't have a place in the intake manifold. Unless I get a water neck with threaded connection I can't really do it. I am using the current place in the intake for my water temp gauge sender.

Originally Posted by piecesparts

I spent a lot of money on my engine and I put in an aftermarket radiator and dual electric fans to keep it cool. The design of the fan switch is up to the buyer, but you definitely want one to work when you need it. Cooling an engine that is cooled by water is to move the right amount of air across a finned coil that has the water in it to supprt effective heat transfer. Actually an electric fan is better than many engine driven fans for a couple reasons. The first being that the fan continues to run at the speed that it was turning at 60 MPH with the car at dead stop, thus assisting in cooling the engine faster. Also the removal of the fan from the engine provides for approximately 10 hp more power to be used in the tranmission and this gains a little gas mileage. Finally, COLD weather, the lack of a fan turning on a cold morning, will allow the engine to heat up to temp faster.

I too have spent a great deal of money on my stroker engine. I want to make sure it is cooled properly. My radiator is a custom aluminum build from Wizard Cooling. I have dual SPAL fans set up in it with a single thermostatic switch in the radiator. I'm just not sure the switch is properly located.

Originally Posted by piecesparts

My fan switch has a dual fan speed capability which turns the first fan on at a speed only necessary to keep the temp at the point that I set it for. If the temps goes up, the fan switch increases the fan's speed and then if really hot, the second fan is started to assist. I have yet to see the second fan run.

Both trucks in the attached pictures have aftermarket SPAL fan sets. The white truck has the fans behind the factory radiator and I used that truck for daily work (summer and winter driving), the black truck has a 400+ hp stroker engine behind the SPAL fans and an aluminum radiator that has been all over the country in more than one Hot Rod Power tour. I am happy to say they have supported me well.

Can you please provide me with more information regarding your fan switch set up. Is it a single switch that has the capability to turn on two fans separately? I'm wondering if I need two separate thermostatic switches to run the two fans.

[Classic Heartbeat]

Classic Heartbeat - You are answering your own argument...if the water in the engine is under 180 degrees then there is no need to cool any water in the radiator.

Why would you not cool the water in the radiator? When the water in the the engine reaches 180 it is exchanged with the radiator water. So the water in the engine is now cooled water lowering the temp of the engine. The water in the radiator is hot water and needs to be cooled off. If not the next exchange is exchanging hot engine water for hot radiator water. Why is the radiator water hot? Because the fans turned off the exact moment the exchange happens because the engine read cooler. This sets you up to at the very least an engine running hotter than it should or worce an overheating.

If it is time for an exchange, then the Tsat opens and at the same time the fans come on.

If the fans come on when the water is exchanged but turn off once the water is exchanged there isn't time for the fans to adaquitly (spell) cool the water.

If the water in the radiator was not cooled, then it would still be above 180* in the engine...and the fans will remain on.

My point exactly. Now you have set up a situation where the engine temp and radiator temp are the same. Rendering the radiator useless and setting up for overheating.

My engine sure isn't overheating...

It wouldn't as long as you are driving down the road. Then the air forced through your radiator by the simple fact that you are moving is cooling the water in the radiator. This is why people do not have problems with overheating untill they get stuck in traffic. Not moving either fast enough or often enough to keep the radiator cool.

Electric fans are designed to push or pull air through the radiator even if the vehicle is stopped. You have to have air flow through a radiator in order for it to cool the water inside. Stagnet or slow flowing air will not do it. WES

[derotoreut]

OK I'm NOT doubting you. I'm just trying to understand the logic. Why do instructions from vendors like Painless and Be Cool (and others) tell you to install the thermoswitch in the head or intake manifold? See link for instructions:

http://static.summitracing.com/globa...ss_install.pdf
http://static.summitracing.com/globa...nstruction.pdf

My thermostatic switch is not a probe type that gets shoved into the fins of the radiator. Its has a NPT connection (I believe 1/2") for threading into place. I currently have it installed in the radiator, as you can see by the pictures. I just want to make sure this is the best location because these vendors are saying to place it in the head or intake.

My other issue is the location of the temperature gauge sender, which is typically installed on the driver side head. My sender will not fit there, so I had it installed in the intake manifold. Is this OK? You can see it sitting on the intake next to the place where it was installed.

[Andy4639]

It depends on if you want the fan's to kick on with motor temp or water temp.
If you want to keep the motor temp down hook it in the block are the intake.
I like the side mount on the drivers side of motor.
But the main thing the fans do is draw air through the radiator so it cools the water off better.

[WIDESIDE72]

Originally Posted by Andy4639

It depends on if you want the fan's to kick on with motor temp or water temp.
If you want to keep the motor temp down hook it in the block are the intake.
I like the side mount on the drivers side of motor.
But the main thing the fans do is draw air through the radiator so it cools the water off better.

X2
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[derotoreut]

So it's OK to install the electric fan thermostatic switch in the radiator (as in my picture), and the water temperature gauge sender in the intake manifold?

[WIDESIDE72]

Not to be argumentative, but you are actually trying to coolthe ENGINE, not the water... Ion my Malibu with a 383 I had it in the head...
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[BMERDOC]

As long as the fan switch is as close to the thermostat as possible, in the manifold by the tstat, in the thermostat housing or in the radiator you'll be fine. I would install the temp gauge sender as close to the thermostat as I can get it. In the manifold or the thermostat housing would be great.

[72 K20]

Not trying to hijack ,,,, what are the details on your serpentine setup ?


Thank You ! Tom

[volksworld]

any production car with an electric fan that i have ever worked on has had the fan switch in the radiator... factory engineers must know something...depending on temp range of the switch you could have fan running with thermostat still closed if switch was on engine...which would be as effective as hot wiring the fan and letting it run all the time...or putting the steel one back on...

[pumpkin]

The location of the fan switch depends on how stable a temp. you want the engine to run at, and how often you want the fan to cycle on and off. If it is mounted in the engine, the engine temp will remain more constant, and be able to cool more eficiantly. If it is in the rad, the engine will get to, say 190, and then a while later the rad will get to 190. By the time the rad is at 190 the engine could be at 210. Both locations will work, but if you want the engine to run at a certain temp, you will hae to play around with sending unit temps. I prefer to mount them in the engine.

[derotoreut]

Looks like I started a pretty good debate between locating the fan thermostatic switch in the radiator or on the engine head or intake. Everyone seems to make valid points either way. It is interesting because many vendors that sell the thermoswitches tell you to install them in either the head or the intake. Then there are those that have probes that require insertion into the fins. I'm wondering if the switches like those put out by Be Cool or others require placement in the head (or intake) because of the temperature range? Keep your comments coming. This is good info.

[ulakovic22]

It should be in the head or manifold. It's a closed system, so at some point the temperature of the water should stabilize and be the same throughout (radiator/engine), but I personally care about how hot my engine is running, not how hot the radiator is. If you keep the engine happy the radiator will be fine, same can't be said the other way.

[Andy4639]

I did a google search and found this response.

Most engine functions are affected by the coolant temperature. Determining whether the engine is hot or cold is largely dependent on the temperature of the coolant. An accurate temperature signal to the PCM is supplied by the coolant temperature sensor or Engine Coolant Temperature (ECT) sensor. The coolant temperature sensor is a thermistor mounted in the engine coolant stream. A thermistor is an electrical device that varies its resistance in relation to changes in temperature. Low coolant temperature produces a high resistance and high coolant temperature produces low resistance. The PCM supplies a signal of 5 volts to the coolant temperature sensor through a resistor in the PCM and measures the voltage. The voltage will be high when the engine is cold and low when the engine is hot.

[ItsRandy]

Use an adjustable solid-state fan controller and it doesn't matter where you put the sender as long as it reads the engine/coolant temp. You can adjust where your fans come on as long as you have a good temp reference point. I think the temp gauge needs to be "under" the thermostat in the intake manifold. I had mine in the head (Dakota Digital gauges) and "saw" a pretty good hot spot and heat soak from the headers.

[Classic Heartbeat]

Are we running air cooled engines? Explain to me how the little electric fans we put on the front or rear of our radiators blow enough air to cool a water cooled engine. (and add to that fact that they are blowing air through a hot radiator first.) The fact of the matter is, they don't. If your fans come on when the water in the engine is lets say 180, and you have a 180 thermostat the heated water in the engine gets flushed out and cooled water from the radiator replaces it. So now the water in the engine is lets say 150. So the temp sender for the fans (because it is placed in the head or somewhere else in the engine) tells the thermostat again for the fans to turn off the fans. How does this make sence? You now have 180 water in the radiator that needs to be cooled befor it cycles again and the fans are shut off. They shut off because the sending unit wrongly placed in the engine told the fans to shut off because the water was cooled down. So now you will have 180 water in the radiator to replace the 180 water in the engine. How does this cool the engine? The answer is, it doesn't. The only reason that the water is any cooler in the radiator is because of ambient temp air flowing through the radiar with isn't enough, or we wouldn't need fans or shrouds to direct air through the radiator. WES

[Classic Heartbeat]

Sometimes companies come up with and sell parts just for asthetics or just to have another part to sell. WES

[derotoreut]

Originally Posted by ItsRandy

Use an adjustable solid-state fan controller and it doesn't matter where you put the sender as long as it reads the engine/coolant temp. You can adjust where your fans come on as long as you have a good temp reference point. I think the temp gauge needs to be "under" the thermostat in the intake manifold. I had mine in the head (Dakota Digital gauges) and "saw" a pretty good hot spot and heat soak from the headers.

This is one of my concerns. Since I have a 465 HP stroker engine with AFR aluminum racing heads and headers, I'm thinking this engine may run hotter, and expect this might happen. I would prefer not to place neither the fan thermostatic switch nor the temperature gauge sender in the head. Keep the comments and opinions coming. Thanks.

[dwcsr]

I'm not getting into the semantics of cooling water or engines the end result is cooling the engine parts.

The most accurate temp readings are in the head or manifold where the heat is generated. The notion of your engine being to hot for a switch in the head doesn't make sense unless I miss read it. Water temps vary greatly through out the motor and radiator as much a 100 degrees. The Tstat keeps your engine at a minimum temp and the fan stat turns your fan on at a minimum temp to help regulate that temp. If you don't want the switch in the motor then you need an adjustable with a probe in the radiator so you can calibrate it to the gauge.

If you want your fan on at 185 then put a 185 fan switch in the head and use a 170 Tstat and your done. Don't over think this your not launching a shuttle.

All fan switches are +/- 5 degrees for the expensive ones and +/- 8 degrees for the cheap $15 ones. That means they could come on at 185 one time and maybe 193 the next and 178 the next. So don't cheap out the the switch

[71Sixer]

^^x2...my electric fan swith is a 180* switch and it is located right next to the Tstat on the intake. When the coolant and engine temp reaches 180, the fans come on. My temperatures remain steady at 180* to 185* on the temperature sender.