Have a '73 350 4-speed and will be installing an aluminum radiator with cooling fans. These are controlled by a temperature sensor, where on the engine should it be installed for proper operation. Thanks in advance.

 

Use Manifold Port Or One In The Head Opposite Temp Sender

 

They come in several flavors. Some use a sensor on the radiator itself and some in the radiator inlet hose and some with a sensor on the otor. If yours comes with a sensor on the motor the most common place to put it is the sensor hole in the passenger head.

 

I have mine in the intake port. Works fine there.

 

The engine gets hot before the radiator. So you figure it out! Sensing the radiator temp is sorta like looking for a gas station after you run empty. Use the cylinder head port as previously suggested. The only thing I hate about that location is the bridge of wiring from the cylinder head. If you jump from the sensor to the fire wall you create another opportunity for broken connections. Its also VERY close to the exhaust manifold. P.S. the Passenger side cylinder head has the plug you need to remove to install the sensor.

 

Sensing the temp at the radiator, specifically at the radiator exit is not as odd as it sounds. The fans are there to cool the coolant in the radiator, not the engine. The fans really serve no function other than that. When your running down the road, there should be lots more air running thru the radiator than the fans can produce, so if the coolant is cooling to below the trip point on the sensor and the sensor is at the radiator exit, the fans won't run.
If the free ir is not enough to cool the coolant down, then the fans will run.
The system will work well either way, but there may be some argument which metood is "The Best"

 

Thanks for all the information.

 

If you buy a thermostat housing for a 79 at Autozone for $8.00 or so it has a port that a temp sensor will screw right in to. It is a close fit under a dropped air cleaner but it fits. You can run the wiring along the valve cover back to the firewall.



Rick B.

 

G'day,
My 1983 V8 Holden Commodore has the temp switch in the radiator. Although the car originally had a clutch fan like my '74 Vette, I fitted a Ford Falcon twin electric fan shroud and sent the trip wires to the sender in the radiator. When I fitted a 16" single electric fan to the Vette, I fabricated a fibreglass shroud to mount it and as the relay/switch assembly had a capillary type sender, I fitted the sender between the fins under the top hose inlet and it works just fine there.

I agree with SIXFOOTER in that the radiator is the best place to fit the sender for the electric fans. From personal experience with two completely different GM V8 cars, this works just fine.

Regards from Down Under

aussiejohn
19 months to go

 

The exit is where it should be for the reasons he posted.
Fans are to cool the water, the thermostat regulates the engine temp.
Most very expensive cars have the sensor there. It must also be realistically matched to the running temps.

BTW, I am always mystified by temp switches placed in the head.

Here is a quote from one of numerous similar threads.
Unless, they are running a 160° tstat and keeping that temp in the head (which is very doubtful), then the fan is coming on and never shutting off.

 

i think as long as your temp sensor is in your head , manifold or your left side of the radiator then its not going to make a difference at all ... the temp variation between all these locations wouldnt be worth mentioning.

if it was on right side of the radiator then yes i could maybe see some concern . i would rather know what my temp is measured when its at its hottest rather than its coldest. in my vet i have my sensor in the front of the manifold on an airgap right in front of the thermostat. on another 350 in my other car its on the right head. they both run at about 185- 190 so how different could it be?

 

I believe that the thermostatic controller SHOULD be on the right side of the radiator, measuring the radiator exit temp.

In an engine driven fan, all temp control is is provided by the engine thermostat. This allows coolant flow when above a certain temp and restricts it at all other times. This same system remains when the vehicle is converted over to electric fans. If electric fans came on with the ignition, the system would be perfectly analogous to the engine driven system.

However, it is desireable that electric fans not run continuously. They are turned off to save wear and tear on the fans and charging system, to increase mileage, and to reduce noise. The goal of thermostatically controlled fans is to cycle the fans, providing cooling air when needed and shutting off at all other times.

Having the fans controlled by a temperature switch in the engine (upstream of the engine thermostat) will only give the switch a reading modified by the engine thermostat. If you have a 180 degree thermostat in the engine, setting the "off" temperature of the fan controller to 180 degrees or less will result in the fans running continuously after the vehicle is warmed up. Setting this "off " temperature to something above 180 degrees will turn the fans on only after the engine is in the first stages of overheating. Neither of these is desireable.

The proper way to control an engine's temperature is to allow the primary control system, the engine thermostat, to work efficiently and give it a resevoir of coolant at as low a temperature as possible to allow ithe engine thermostat to continuously adjust the engine's temperature. The resevoir of lower temperature coolant is the contents of thee radiator. The fans are the method of removing heat/lowering temperature from the radiator. To control this process of heat removal you must measure the output temperature of this portion of the system. Put the thermostatic controller be on the right side of the radiator, measuring the radiator exit temp.

 

It's the temp sensor for the temp gauge that should be in the head or tstat housing to measure the hottest engine temp.

The temp switch controlling the fans is the one to put on the radiator exit. A 20-30° temp difference is ideal, also to insure that the coolant is not too cold re-entering the engine. This still a rather crude, but still the best way of controlling it on that generation of small block.
The temp switch that GM put in the passenger head is set very high for that reason.

 

This toppic always gets a lot of attention. I think its a good thing, the cooling system is often misunderstood even by guys that have a lot of experience. I always learn something in here

 

The threaded hole in my Dewitts radiator is near the upper radiator inlet on my radiator. It works very well there.

 

....and so do a couple hundred other customers that have used them. Measuring the hot coolant coming out of the motor is going to tell you exactly what is required from the fans. Many Corvettes use this source to feed the temp guage as well, so I guess that's an important number.

 

Then the thermostat housing should also be a good place.

 

It's a great place

 

what about when a thermostat stops working and stays shut which is not uncommon. wouldnt a sensor in the radiator not be such a good idea as the coolant almost stops circulating in the entire system but the reading you would be getting from the sensor would be normal as the radiator water stays constant temperature or even drops while the coolant in your motor is cooking.you wouldnt know until its too late.

 

But you still have a temperature gauge that will show the increase in temp (in most cases)