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Hot engine fan spinning, what would you do:

  • Keep the engine running till the fan stops.

    Votes: 8 20.5%
  • The hell with it, thats what the engine is made for.

    Votes: 31 79.5%
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Discussion Starter #1 (Edited)
Hey guys, what do you guys think is best in the following situation:

You have been driving during warm weather, you arrive at your destination. Want to stop your engine but you notice that your fan is spinning.

a) Keep the engine running till the fan stops.
b) The hell with it, thats what the engine is made for.

Personally I would opt for B. But if I compare this with a turbo on a car, people say its better to let it cool before shutting down the engine.
 

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I myself have wondered which is better. I used to let it run until the fan stops, but now, even if the fan is running I just shut it down.

I really don't think it hurts anything to just turn the engine off whether the fan is running or not.
 

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If it was necessary for the fan to cool the engine then there would be a relay to keep it going like on a car, or at least a "WARNING" in the owners manual.

I just cut mine off.
 

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Discussion Starter #4
If it was necessary for the fan to cool the engine then there would be a relay to keep it going like on a car, or at least a "WARNING" in the owners manual.

I just cut mine off.
Yeah probably, also when the engine is cut off, the water pump isn't pumping.
 

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Actually, and at the risk of stating the obvious, the fan only comes on because the Coolant-Temperature Sensor has detected a temperature that exceeds a pre-determined, pre-set parameter. The fan is then automatically activated and is designed to stay on until the coolant temperature is restored to somewhere within its "normal" operating range.

Now, and normally, the coolant will remain in its liquid-phase so long as it is circulating through the engine core, but from the moment that an overly-hot engine is shut-off, the coolant within the engine core will continue to absorb heat and, if it's already near its boiling-point, it will "two-phase" (go from a liquid to a vapor), causing the pressure in the cooling system to increase rapidly, which causes the pressure-relief valve to "pop-off" and release some vapor and coolant into the coolant reservoir. As the non-running engine continues to cool, the pressure in the system will continue to drop, to the point that a low-pressure condition will develop and liquid coolant will then be drawn back into system from the reservoir, restoring everything to normal.

In the strictess sense, it would always be operationally optimal, when reaching a destination, to allow the engine to continue to run, at idle, until the fan kicks-OFF; especially on a really hot day when the fan has been running continuously just before you shut the engine down. I say this realizing that most of us (myself included) lack the patience to stand there beside our idling machines, waiting for the fan to shut-off. When I come home to my garage and park, if the fan is running, I'll leave the engine running while I take my riding gear off. By then, invariably, the fan has shut-off and I can kill the engine.

It's unfortunate that Honda's engineers didn't elect to allow our fans to keep running after a "hot-engine-shut-down" (a la most car systems), but I can only speculate that they did this in the interest of saving our already-marginal battery power; what's a properly-cooled engine worth if you don't have enough cranking-power left to start it! Just another example of the kind of compromises that oft-times enter into the design process.

Anyway, my two-bits, FWIW.......................

Cheers
 

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Good info Bar. I've never heard my fan running. Is it loud enough that I would definitely hear it or can it go undetected?

*I only have a hearing problem when my wife is talking. Maybe the fan and my wife's voice sound alike.
 

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on a turbo charged engine, you let it idle to cool down the turbo not the engine, if you didnt let the turbo cool down, the oil would burn off in the turbo and cause carbon build up on the bearings, or bushings, and in time cause turbo failer. now on your Fury, just shutting it off would be ok, letting it idle till the fan turns off is ok too, as your letting the cooling cool down and flow through the engine. but eather way is ok, Now the key to keeping it running cooler should have been asked, One is changing the oil to synthetic oil, like AMSOIL 10w40 high performancem and you could add, water wetter, or change to engine ICE coolant. witch does help lower engine temps from 10 -20 degs when riding. your fan would only come on if sitting still in traffic with no air flow for cooling, also cooler temps when riding make for better power and longer life. I run AMSOIL 10w40 and ENGINE ICE on a dyno have seen 13 degs lower cylinder temps.
 

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As speedy said,

pick up a bottle of "water wetter" and put it in the coolant system. its an awesome product and I have used it for years in all my vehicles and I have NEVER experienced an overheating issue.
it lowers your coolant temp by as much as 20%

My fan rarely comes on and usually only in extremely heavy stop and go traffic.
 

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Discussion Starter #9
I would say there is always a bit oil in your cylinder just to lubricate it, so if this oil would burn up by a temporary increase in temperature. So in time perhaps it could add up.

Just thinking aloud.
 

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Good info Bar. I've never heard my fan running. Is it loud enough that I would definitely hear it or can it go undetected?
Running down the road, at any significant speed, you'll probably not hear it (helmet, wind-noise, pipes, etc.). But at low-speed, or idling, you most certainly would, unless your pipes are earth-shatteringly loud.

Cheers
 

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I would say there is always a bit oil in your cylinder just to lubricate it, so if this oil would burn up by a temporary increase in temperature. So in time perhaps it could add up.
Interesting............I would be very-much interested in any supporting documentation for the concept.

Cheers
 

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the fan only turns on when engine coolant temps reach 220 or higher, when riding and having air flowing over the rad, you should never hear the fan if you do you got poor air flow over the rad. like said before, should only come on at slow speeds in traffic or sitting at a traffic light for a good amount of time. if the fan is coming on alot coolant maybe low, or a bad coolant temp sensor.
 

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Good info Bar. I've never heard my fan running. Is it loud enough that I would definitely hear it or can it go undetected?

*I only have a hearing problem when my wife is talking. Maybe the fan and my wife's voice sound alike.
I can barely hear mine at idle... I mostly feel the hot air it pushes on my legs when stopped.
 

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Discussion Starter #14
Interesting............I would be very-much interested in any supporting documentation for the concept.

Cheers
I copied this from a website:

Oil is a tremendous coolant. In the engine, the oil cools the underside of the pistons, valve springs, camshaft, rods, crankshaft and bearings. The oil picks up the heat from the combustion of fuel, as well as friction, and takes it away (no matter how good the oil may be, there is always friction). The volume of the oil in the crankcase helps transfer the heat, but where a car/truck is used in high temperature climates, for hauling trailers or heavy loads, an engine oil cooler is sometimes recommended.

Thus considering the info above, I would say that if you leave the pistons and cylinders hot they could possibly burn up a tiny amount of oil.

Perhaps clueless or any other mechanic could confirm or deny this?
 

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............Oil is a tremendous coolant. In the engine, the oil cools the underside of the pistons, valve springs, camshaft, rods, crankshaft and bearings. The oil picks up the heat from the combustion of fuel, as well as friction, and takes it away (no matter how good the oil may be, there is always friction). The volume of the oil in the crankcase helps transfer the heat, but where a car/truck is used in high temperature climates, for hauling trailers or heavy loads, an engine oil cooler is sometimes recommended..............
Ah, so. In the context of the above-cited reference , I understand your point. In fact, I am aware of a couple of motorcycle models, sport-bikes as I recall, that share the cooling duties just about equally between the oil AND water circuits, but they have internal oil-spray nozzles and separate oil coolers, which our Fury's do not. Anyway, just an observation..................

Cheers
 

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Running down the road, at any significant speed, you'll probably not hear it (helmet, wind-noise, pipes, etc.). But at low-speed, or idling, you most certainly would, unless your pipes are earth-shatteringly loud.

Cheers
I dont think the fan would ever come on running down the road? Would it?
 

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I dont think the fan would ever come on running down the road? Would it?
Potentially, on a hot, humid, day, or while running uphill for an extended period, then yes, it would. In fact, mine comes on every time I run up the hill to Tahoe, even on a chilly day. Just FWIW..........

Cheers
 

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with any vehicle if you have a mechanical coolant pump, leave it run until fan shuts off. If you shut it off or even kill the engine and leave ignition on until fan shuts off the water pump isnt circulating so you have coolent hitting high temperatures in the cyl. jackets and heads (potentially causing steam pockets) from the cyl. heat radiating into the coolent but not getting replaced with cooler antifreeze.

If you have an electric coolant pump then it will circulate aslong as that circuit is on so will be more beneficial to shut engine off with the kill switch and allow the coolant and fan to circulate until cooler temps are achieved.
 

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As speedy said,

pick up a bottle of "water wetter" and put it in the coolant system. its an awesome product and I have used it for years in all my vehicles and I have NEVER experienced an overheating issue.
it lowers your coolant temp by as much as 20%

My fan rarely comes on and usually only in extremely heavy stop and go traffic.
i have it in my race car and fury...works awesome
 

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The "water-wetter", you just added to your existing level of coolant, assuming it has the correct level of coolant, or you have to take out or flush out some of the coolant out of your cooling system, in order to compensate for the extra amount of liquid (water-wetter) you are adding to the cooling system?

I want to use it on my Fury, but want to make sure I am doing it right.
 
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