Shutting Down the Engine when Radiator Fan is Running?


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This Sunday I & one of my friend (who is equally interested in automotive) came home after driving my Santro for about 15 odd kms through traffic. When we reached my parking place he saw that the radiator fan (which cools the engine) was running & I switched off the car.
He just shouted stating that this is one of the biggest harm I’m doing to my car engine. As per him it is not a good practice to switch off the engine when the radiator fan is working. He said that during such instances one should put car in Neutral & wait for a minute or so till the fan goes off & then switch off the engine. Although he was not able to technically prove the reasoning behind this but he stated that he has got the same info from his mechanic who works at Maruti A.S.S

Guys do you know if this holds any truth with any technical reason? Please suggest
 

TSIVipul

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Re: Shutting down engine when radiator fan is running

Well,being true,even I too have not paid concern towards it,sometimes I shut it sometimes I let it run.
I too have the same question,should we?
 
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Re: Shutting down engine when radiator fan is running

That is the first time I am hearing this! Technically, radiator is taking the heat out of the engine parts. Coolant which has been through engine is hot and is fed into radiator, which passes it through many pipes to take the energy and make it cool. To increase the dissipation of energy coolant fan is used.

Now I can understand that when you shut off the engine the coolant fan will shut off and coolant will not be circulated through the engine. This *might* cause some damage in the long run.

This practice is mostly followed in cars having turbo. As a good practice one should always idle before moving from cold start and switching off the engine after long drives.
 
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Re: Shutting down engine when radiator fan is running

I have seen in the user manual it states for Turbo Engines. the engine should be run in ideal for atleast 1 minute before and after starting and stopping the engines. This needs to be specially addressed in winter as the temprature is cold. One should not start the engine and drive immediately as the temperature of the engine is still cold and would harm the engine in long run.
As far as the radiator fan is concerned I personally let the engine run for some time till the radiator fan comes to a stop. But sometimes I also shut the engine off and turn on the radiator fan but at this time the fan runs on battery. I believe that the fan just cools the radiator.
Will wait for our experts to throw some light on this topic.
 
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Re: Shutting down engine when radiator fan is running

Hi all,

The reason the radiator fan is installed is to cool the Engine coolant when the Engine is running. As rightly pointed out by Radhesh, a cold engine if loaded immediately after starting will damage the engine in the long run however when we stop the car the main cause of heat formation i.e combustion is absent and therefore it does not matter if the radiator fan is On or OFF.

B
 
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Re: Shutting down engine when radiator fan is running

I don't see there is any harm in killing the engine when fan is running. The purpose of radiator fan is to cool the radiator. Now, when you have killed the engine itself, radiator can take it's own sweet time to cool off. So, no need to let the fan running and wait to switch-off the engine only after the fan stops.

freakdude.
 
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It is always a good habit to have the radiator fan complete its cycle as this will regularize the temperature evenly across all the connectors through which it travels through.
The main function of this fan is to circulate Hot coolant to mix with existing coolant and minimize the temperature. If this process is stopped, a serious damage can be expected..
My advice, let the cycle finish if it has started.
 
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Good practice is to wait till the radiator fan have stopped its running.

when its running , there is cycle of hot water coming out from the engine to radiator and same being cooled while previously cooled water enters. .
in this cycle at idle condition - that is when you are about to park , the engine reaches its minimum temperature .

Any object must be cooled slowly.
so this practice is advised . Fiat uno has its fan running even after the key is removed.

but every time one cant hear the fan's sound.

best practice is idle some time before parking and starting!
 
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So Ilango,
Is it fine to kill the engine even if the radiator fan is running:
1) After coming to hault run the engine for 1 min approx.
2) Kill the engine by turning the engine off.
3) If the radiator fan is still running as the engine is still hot can we kill the engine and then only run the radiator fan on battery.
4) At this time the engine is off but the radiator fan is still running for some time till the engine reaches optimum temperature.

Ilango is this way of operating the engine causing any harm to the engine ?
 
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So Ilango,
Is it fine to kill the engine even if the radiator fan is running:
1) After coming to hault run the engine for 1 min approx.
2) Kill the engine by turning the engine off.
3) If the radiator fan is still running as the engine is still hot can we kill the engine and then only run the radiator fan on battery.
4) At this time the engine is off but the radiator fan is still running for some time till the engine reaches optimum temperature.

Ilango is this way of operating the engine causing any harm to the engine ?
First point is , idling the engine is good practice.
radiator fan , running on battery after the car is switched off , draws power from battery.

Not a harm if you switch off the car without noticing anything. just after a mad rush/highway run etc kind of , idle the engine. that is best , everything will be taken care off
 
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I have all along practiced allowing the radiator fan to come to a halt before switching of.

My uncle (he is no more) who was a rally driver and from I have received my inspirations on driving had adviced this to me way back and had explained to me also. Unfortunately have forgotten his explanation but remembered his practice.
 
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Simply running the fan while the engine is off is silly. Itll just cool off the water standing in the radiator. But when the engine is running the cooled water is pumped back into the block cooling it further. Ive also heard "idle engine until fans shuts down" but without a proper scientific explanation.
 
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The coolant circulates because the pump is pumping it, if the pump has stopped pumping, only the liquid in the radiator will get cooled. When a car is parked, the engine is already near the idling speed with spurts of power to get it to the required position. This does not generate as much heat as would a car running on a road at a speed and therefore IMHO it does not matter whether one waits till the fan is switched off. Again since the coolant entering the engine cooling spaces is at a regulated temperature, this temperature will not rise as much as to generate any vapour even if the car is stopped and the coolant is not flowing after that. These factors have already been taken into account at the design stage and the amount of coolant, the pumping rate are designed with the amount of heat generated, sudden stoppage etc. being taken into consideration.
I would say that waiting for the fan to stop would not increase engine life and would not be deteriorating the engine. The toughest time for a engine is at the start, when the engine is cold and the lubrication in the cylinder and the bearings is at Boundary Lubrication condition.
Sorry for the jargon but its true. I hope this clears the matter.
B
 
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I am aware that this is one of the reason why Turbo charge engine is asked to wait for 1min after and before a complete enginee start/stop.

But This is the same reason by Petrol MPFI enginee is asked to start without leg on peddal?
 
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