Fred W B
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| posted on 20/6/23 at 01:40 PM |
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Coolant temperature sensor position - Fan operation
Simple question but I am doubting myself. Where to position the coolant temperature sensor to operate the radiator cooling fans in a mid engined car
with the radiator at the front of the car?
I plan to put the temperature gauge sensor for the dashboard gauge in the swirl pot where the water exits the engine, do I put the fan temperature
sensor at the same place, or in the outlet pipe from the radiator? The latter was my initial thought.
Cheers
Fred W B
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nick205
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| posted on 20/6/23 at 02:42 PM |
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Can't answer your question.
Don't mid-engine cars often have multiple radiators?
Are they all for engine coolant or a mix of tasks?
Where do OEM Mid-engine cars fit the coolant temp sensors?
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ken555
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| posted on 20/6/23 at 03:05 PM |
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I have a dual switch/fan close to the exit pipe on the radiator.
Switches at 2 temps, so one or both fans run.
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adithorp
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| posted on 20/6/23 at 03:09 PM |
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Short answer... Either.
At the engine you'll need a higher switching temp than at the rad'.
If you go rad' then from what I can remember, the switch is normally on the inlet side.
It might take a bit of experimentation to find the best switching temp. I used a twin temp switch (designed for 2 fans) when improving the system on
an MK and that allowed me to try 2 different settings without changing the switch (and losing coolant).
Of course you could do both. Mine are switched by the ECU based on engine temp but my rad does have a switch in it that I could wire in (it's
just used as a bung currently). Given the long pipe run that might cover any anomalies you get.
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Fred W B
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| posted on 22/6/23 at 08:28 AM |
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Thanks for the responses all, great to see activity on here, it s been very quite for a long time now.
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mgb281
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| posted on 22/6/23 at 10:22 AM |
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If you are installing one on the radiator then on the exit pipe otherwise you will be running the fan when normal ram effect air would have cooled it
anyway
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Mr Whippy
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| posted on 22/6/23 at 01:03 PM |
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why not one on the engine since that's the thing that's going to melt? Most I've seen are in the side of the block so should always
have a head of water above it. If it was only in a hose and the water level dropped or there was an air lock, then the sensor would not be submerged
and then the fan doesn't come on leading to overheating and more air/steam in the hose and a runaway effect. Chernobyl.
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mgb281
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| posted on 22/6/23 at 02:27 PM |
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Putting one on the engine outlet is okay but will turn the fan on even if normal ram air flow at even low speeds will be sufficient to cool it, you do
need a switch to turn the fan at a lower temperature though. The advantage of having it on the rad outlet or the engine inlet is that it will only
operate if needed, overcooling has no benefit. Most car manufacturers have done this for years. Having it in the bottom hose means that it is always
submerged.
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Mr Whippy
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| posted on 22/6/23 at 02:35 PM |
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quote:
Originally posted by mgb281
Putting one on the engine outlet is okay but will turn the fan on even if normal ram air flow at even low speeds will be sufficient to cool it, you do
need a switch to turn the fan at a lower temperature though. The advantage of having it on the rad outlet or the engine inlet is that it will only
operate if needed, overcooling has no benefit. Most car manufacturers have done this for years. Having it in the bottom hose means that it is always
submerged.
hmm, if ram air was enough to cool the engine it would switch off the fan regardless of were the switch was located, it's the blocks temp that is
important not the rads.
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mgb281
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| posted on 22/6/23 at 07:25 PM |
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quote:
Originally posted by Mr Whippy
quote:
Originally posted by mgb281
Putting one on the engine outlet is okay but will turn the fan on even if normal ram air flow at even low speeds will be sufficient to cool it, you do
need a switch to turn the fan at a lower temperature though. The advantage of having it on the rad outlet or the engine inlet is that it will only
operate if needed, overcooling has no benefit. Most car manufacturers have done this for years. Having it in the bottom hose means that it is always
submerged.
hmm, if ram air was enough to cool the engine it would switch off the fan regardless of were the switch was located, it's the blocks temp that is
important not the rads.
You haven’t understood at all, the engine is circulating hot water through the radiator which triggers the fan, ram air alone in most conditions is
sufficient. In your case the fan is running needlessly. By having the switch in the bottom hose the fan only comes on if ram air is insufficient,
normally a sensor in the bottom hose is set to turn on at a lower temperature as well to ensure the coolant is brought down to a safe temperature.
If your theory was correct somehow the sensor on the engine outlet would turn the fan off because it knows the coolant temperature at the bottom of
the rad, can you explain how that works?
The block/head temperature is regulated by the thermostat which blends hot water from the engine outlet with cooler water from the radiator, when the
engine is very hot all water circulates through the radiator
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Mr Whippy
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| posted on 23/6/23 at 06:14 AM |
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If your theory was correct somehow the sensor on the engine outlet would turn the fan off because it knows the coolant temperature at the bottom of
the rad, can you explain how that works?
– It doesn’t matter. You’d set the fan switch in the block above operating temperature so that if the block goes beyond that the fan kicks in. Once
moving the coolant temp will always be lower than the switch temp so the fan is off, It will only come on once the air flow is not sufficient on its
own.
The block/head temperature is regulated by the thermostat which blends hot water from the engine outlet with cooler water from the radiator, when the
engine is very hot all water circulates through the radiator
– True but the thermostat opens quite early on at quite a low temperature and has no effect at all once the engine is at or above operating
temperature. Place one in a pan and you’ll see it’s fully open when the water is boiling. Its function is to get a cold engine up to operating
temperature quickly, not to regulate the upper temperatures.
Amusingly there is little difference where the switch is located. Just don’t put it at the top as I have seen some people do.
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mgb281
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| posted on 24/6/23 at 06:54 AM |
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" You’d set the fan switch in the block above operating temperature so that if the block goes beyond that the fan kicks in. Once moving the
coolant temp will always be lower than the switch temp so the fan is off, It will only come on once the air flow is not sufficient on its
own."
Yes but you are you are still running the fan more than you need to, your way that has been used for decades turns the fan on regardless of whether
ram air alone is sufficient.
The block/head temperature is regulated by the thermostat which blends hot water from the engine outlet with cooler water from the radiator, when the
engine is very hot all water circulates through the radiator
– True but the thermostat opens quite early on at quite a low temperature and has no effect at all once the engine is at or above operating
temperature. Place one in a pan and you’ll see it’s fully open when the water is boiling. Its function is to get a cold engine up to operating
temperature quickly, not to regulate the upper temperatures.
Not correct, the thermostat continues to open and close after the engine warms up to keep the water at a constant temperature. Here is a scenario that
illustrates this, imagine that you are driving on a main road on a cold winters day, heavy traffic but moving along at 50 mph. In this case the
thermostat will be only slightly open, the very cold coolant is being blended with hot recirculated coolant to maintain the correct running
temperature. If the thermostat didn't do this the running temperature would be low and thermal efficiency would be lost. This happens on a good
many days from autumn to spring, years ago people took their thermostats out to prevent over heating then wondered why the heater didn't work
Amusingly there is little difference where the switch is located. Just don’t put it at the top as I have seen some people do.
Absolutely correct
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