Cooling Fan

[starkruzen]

To my knowledge, my cooling fan has never activated. Is it just not getting hot enough or is there a malfuntion? How can you test it?

 

Thanks

[skydoc_17]

Start your bike, Let it idle on the side stand for about 15 minutes, that puppy ought to be coming on about then! With the engine running, and moving thru traffic, it is pretty hard to hear it cut on and off. But in your drive way, at idle, you should have NO problem hearing it turn on. To test the fan motor, pull the plug and put 12 volts to it. ( I use a battery charger) 2 Jumper wires from the battery will do the same thing. The only other thing it could be would be the thermostatic switch (fan Switch) that kicks the fan on when the temp. gets too high. Living in FLA. I can't believe that your fan has never come on. Try the kick stand test, then let us know what happened.

Earl

[Monty]

It takes a little bit, as the fan doesn't come on until around 215 degrees F.

 

As said, leave it on the sidestand, and give it some RPMs. Shine a flashlight in there from the left side, and you should see it come on after it gets hot enough.

[midnightventure]

The only time I ever heard mine was after sitting in a line at the bank on a very hot day for several minutes.

[V7Goose]

As others have already said, it takes quite some time at idle before the engine gets hot enough to kick on the fan. When moving, even in the hottest conditions, it will never come on. The fan is not loud, and many people do not notice it.

 

BUT... I have had several people bring bikes to me for tuning where I have found objects lodged in the fan preventing it from turning. Needless to say, this is a very bad thing if you get caught in a summer traffic jam!

 

There are only two ways to test the fan - either find the wires to the sensor, unplug them, and use a jumper to trigger the fan on, or just fire up the bike and let it idle without any external cooling fan. After something like five or ten minutes, the bike will get hot enough to trigger the fan and you will get a big blast of hot air blowing back along both sides of the engine. I always experience this when syncing the carbs before I get done. Watch your dash and the coolant overflow tube while the bike is running - if the fan does not work, the overheat light will come on and coolant will begin to spurt from from the tube. If you shut it down soon after the light comes on, no damage will be done.

Goose

[dingy]

Below is a link to the schematic for the RSV's

 

Fan circuit is located in lower right corner.

 

As Goose said you can pull the connector at the thermostat and jumper the two wires together with a paperclip on the wire connector. Key will need to be in ON position.

 

Or as SkyDoc said you can pull the connection that goes to the fan and put positive on one side and negative on the other, Black wire is ground & Blue wire is positive.

 

Whichever one is easier to get at. To me the thermostat is easier, all you have to do is jumper it.

 

99-09 Yamaha Royal Star Venture Wiring Diagram Rev B.pdf

 

Gary

[starkruzen]

Well, just like you said, cranked it up, set the idel a little higher and in about 10 minutes the cooling fan came on! Well, at least I know it works!

 

Thanks for the help!

[paysaw]

My 83 runs hot.it never boils over and I have the fan mod.Is it a good idea to take my thermostat out?,Thoughts!!!

[V7Goose]

My 83 runs hot.it never boils over and I have the fan mod.Is it a good idea to take my thermostat out?,Thoughts!!!

It is never a good idea to take the thermostat out.

 

First of all, taking a good thermostat out cannot help your bike run cooler unless the radiator is already heavily plugged, and even then, it probably won't help at all. Here is why:

 

The engine and cooling system were designed to always keep the temperature in the correct range. I know on a 2nd gen, the engine actually runs about 10 degrees cooler when the outside temperatures are above 90 than it does when it is in the 70s - proof that the cooling system is not only capable of keeping the engine cool in all conditions, but actively making adjustments based on those conditions. I assume the 1st gens cool just as well if there is not something wrong.

 

So, if the system with the thermostat in place works fine, what can happen if you remove it? First, the engine will not warm up to the proper operating temperature near as fast, even on hot days. This both increases the pollution and adds wear to the internal engine parts. Second, in many conditions, the engine will NEVER reach proper operating temperature without the thermostat resulting in continuing pollution and excess internal engine wear.

 

It is true that even a fully open thermostat still provides some restriction to the maximum flow of coolant, but if the engine is not cooling properly with it in there (assuming the thermostat is operating correctly), it almost certainly will not cool any better with it removed. The most likely reason an engine will not cool properly is a dirty and plugged radiator, which restricts the coolant flowing through it. Removing the thermostat to allow the coolant to flow faster won't help at all if the radiator is what is causing it to not flow. There are a few cases where only some of the passages are plugged, and increasing the coolant flow through the others might help a bit, but even if it does, you are simply on borrowed time before the engine is destroyed.

 

As with other problems that a bike might have, it is always better to actually find what is wrong and fix it than look for a way to hide the problem.

Goose

[wes0778]

It is never a good idea to take the thermostat out.

 

First of all, taking a good thermostat out cannot help your bike run cooler unless the radiator is already heavily plugged, and even then, it probably won't help at all. Here is why:

 

The engine and cooling system were designed to always keep the temperature in the correct range. I know on a 2nd gen, the engine actually runs about 10 degrees cooler when the outside temperatures are above 90 than it does when it is in the 70s - proof that the cooling system is not only capable of keeping the engine cool in all conditions, but actively making adjustments based on those conditions. I assume the 1st gens cool just as well if there is not something wrong.

 

So, if the system with the thermostat in place works fine, what can happen if you remove it? First, the engine will not warm up to the proper operating temperature near as fast, even on hot days. This both increases the pollution and adds wear to the internal engine parts. Second, in many conditions, the engine will NEVER reach proper operating temperature without the thermostat resulting in continuing pollution and excess internal engine wear.

 

It is true that even a fully open thermostat still provides some restriction to the maximum flow of coolant, but if the engine is not cooling properly with it in there (assuming the thermostat is operating correctly), it almost certainly will not cool any better with it removed. The most likely reason an engine will not cool properly is a dirty and plugged radiator, which restricts the coolant flowing through it. Removing the thermostat to allow the coolant to flow faster won't help at all if the radiator is what is causing it to not flow. There are a few cases where only some of the passages are plugged, and increasing the coolant flow through the others might help a bit, but even if it does, you are simply on borrowed time before the engine is destroyed.

 

As with other problems that a bike might have, it is always better to actually find what is wrong and fix it than look for a way to hide the problem.

Goose

 

The Cliff Notes version is the thermostat maintains the MINIMUM engine temp and provides enough restriction, when fully open, so the coolant stays in the radiator long enough to loose enough heat to be able to properly cool the engine.

 

Not sure about the Yamaha radiators, but the cooling systems I have worked on for 33+ years expect the radiator to change the temperature (inlet to outlet) of the coolant in a range of 12 to 15 degrees. If the "drop" is much less than 12 (closer to 0) there is usually said to be a capacity problem. (radiator is too small or externally plugged) if the "drop" is much more than 15 (Further from 0) there is usually a Flow problem. (the radiator is internally plugged, water pump not pumping sufficient flow, or thermostat not opening.)

[starkruzen]

Well said Wes!

[Venturous Randy]

My 83 runs hot.it never boils over and I have the fan mod.Is it a good idea to take my thermostat out?,Thoughts!!!

 

The bypass on the piping below your radiator is the same thing as taking the thermostat out. You could check to make sure it is in the correct place, or change what you have and see how it does. The tops of the letters should point toward the 5 o'clock position, if my memory serves me correctly. And yes, on some vehicles, not enough restriction can cause an engine to overheat as coolant is flowing too fast thru the radiator to be cooled.

RandyA

[KiteSquid]

On 1st gen small block Chevrolet motors (IIRC 1954-2002), if you take the thermostat out the water circulates through the radiator and the front of the engine block, so the rear gets HOT..... This MIGHT be the same situation in our bikes, but I have not really looked hard at the coolant flow....

[V7Goose]

I am not an expert in this area, but personally, I think the idea that too much water flow through the radiator can cause an engine to overheat is nothing but a fallacy. I have seen it repeated in many places, but it defies logic. I think it is nothig more than a bad rumor that people pick up and spread like any other rumor.

 

The engine cooling system is a closed system with heat being added by the combustion on one side and being removed by the radiator on the other. If the two sides are balanced, meaning the radiator is capable of dissipating the same amount of heat that is made by the engine at some minimum gallons per minute (GPM) flow of coolant, then Any greater flow of coolant must work at least equally as well under the same external conditions.

 

Yes, it is true that a fixed volume of water flowing faster through the radiator cannot loose as much heat in one pass since it does not spend as much time in the cooling side of the system, but that argument has almost nothing to do with the actual thermodynamics of the engine cooling. What we are really interested in is the amount of heat the radiator can dissipate over a fixed period of TIME, and this can only get BETTER with faster water flow, not worse. Heat is transferred from the coolant to the air by how much surface area of the radiator is available and how much difference there is in the temperature on each side of that surface. Since neither the surface area nor the air flow changes if the thermostat is removed, then the amount of total heat that is dissipated over one minute must be at least equal to or greater than the amount of heat that is dissipated with a lower flow rate.

 

Think about it this way - the radiator does nothing more than transfer heat from one side to the other until the temperature is equal on both sides. If you INCREASE THE AIR FLOW over the cooling fins you carry away more heat each minute (that is why you have a fan), but only to the extent that there is enough heat being generated on the hot side of the system (and that is why your fan shuts off). If you increase the air flow too much, you can remove more heat than the system can produce over the same period of time (and THAT is why you have a thermostat). Sooooo, if increasing the air flow over one side of the radiator surface cools the fluid on the other side faster, then the reverse must also be true - increasing the water flow over the cooling fins MUST have an equally dramatic affect on the heat transfer, meaning it heass the air faster and, therefore, cools the fluid.

 

But the bottom line is still this: the cooling system is designed to work properly with your motor with the thermostat and all the other pieces in place and working properly. If you remove any of those pieces, your engine suffers.

Goose

Edited July 8, 2010 by V7Goose

[tpalshadow]

Goose, I do understand what you are saying but it raises the question why is there a thermostat to open or close at all? Why not just leave it open all the time and only have a switch that turns the fan on or off?

 

To my knowledge all water cooled systems have a thermostat and you don't want them to be stuck open...definitely not closed. I think the speed at which the overheating occurs is much faster if it is closed, but it can still overheat if stuck open.

 

I would assume the surface area which the liquid covers on the 'hot' side is much larger than the 'cold' side. If you had a big enough radiator where the surface areas were the same than I would say an open thermo would not be a problem.

 

In summary I think the fact that we have a thermostat indicates it needs to operate properly.

 

[Freebird]

I'm sure that Kent will answer this but I've always understood that the thermostat serves two purposes. In automobiles, it enables the water to reach a high enough temperature for the heater to do its job. Even more importantly though, in automobiles and on motorcycles, the engines are designed to run more efficiently within a certain temperature range. The thermostat keeps the engines within that range.

[Guest tx2sturgis]

I am not an expert in this area, but personally, I think the idea that too much water flow through the radiator can cause an engine to overheat is nothing but a fallacy. I have seen it repeated in many places, but it defies logic. I think it is nothig more than a bad rumor that people pick up and spread like any other rumor.

 

The engine cooling system is a closed system with heat being added by the combustion on one side and being removed by the radiator on the other. If the two sides are balanced, meaning the radiator is capable of dissipating the same amount of heat that is made by the engine at some minimum gallons per minute (GPM) flow of coolant, then Any greater flow of coolant must work at least equally as well under the same external conditions.

 

Yes, it is true that a fixed volume of water flowing faster through the radiator cannot loose as much heat in one pass since it does not spend as much time in the cooling side of the system, but that argument has almost nothing to do with the actual thermodynamics of the engine cooling. What we are really interested in is the amount of heat the radiator can dissipate over a fixed period of TIME, and this can only get BETTER with faster water flow, not worse. Heat is transferred from the coolant to the air by how much surface area of the radiator is available and how much difference there is in the temperature on each side of that surface. Since neither the surface area nor the air flow changes if the thermostat is removed, then the amount of total heat that is dissipated over one minute must be at least equal to or greater than the amount of heat that is dissipated with a lower flow rate.

 

Think about it this way - the radiator does nothing more than transfer heat from one side to the other until the temperature is equal on both sides. If you INCREASE THE AIR FLOW over the cooling fins you carry away more heat each minute (that is why you have a fan), but only to the extent that there is enough heat being generated on the hot side of the system (and that is why your fan shuts off). If you increase the air flow too much, you can remove more heat than the system can produce over the same period of time (and THAT is why you have a thermostat). Sooooo, if increasing the air flow over one side of the radiator surface cools the fluid on the other side faster, then the reverse must also be true - increasing the water flow over the cooling fins MUST have an equally dramatic affect on the heat transfer, meaning it heass the air faster and, therefore, cools the fluid.

 

But the bottom line is still this: the cooling system is designed to work properly with your motor with the thermostat and all the other pieces in place and working properly. If you remove any of those pieces, your engine suffers.

Goose

 

 

Goose, I would tend to agree in any normal fluid dynamic scenario thru a simple smooth-bore pipe, but I think your ignoring one thing: Cavitation.

 

When coolant is allowed to flow too rapidly, (too much flow) thru the small convoluted water passages within a radiator, the fluid cavitates severely within the passages of the radiator and heat transfer efficiency is LOST, not gained.

 

I'm no expert either, but I have heard for years that a smooth, controlled flow of coolant (thru the radiator) is much more efficient, and provides more cooling, than a rapid, uncontrolled flow of coolant, due to this cavitation.

 

[V7Goose]

Don is exactly correct - the engine must operate within a specific design range for lowest pollution, best fuel economy, and longest life. The thermostat lets it heat up to that range the fastest, then keeps it in that range under different outside conditions.

 

The engine life issue is because all metals expand at different rates and by different amounts. When the engine is designed, they have to select clearances between the various parts that will allow it to run when started cold, keep running when one metal, such as an aluminum piston, expands faster than the metal it is near (such as a steel cylinder wall), and still maintain all the acceptable clearances after all metals have completely heated and expanded to their maximum size.

 

All that changing of metal sizes and clearances is why water cooled engines have closer tolerances and longer life than air cooled engines. But ONLY if they have a properly operating thermostat and cooling system!

Goose

[V7Goose]

Goose, I would tend to agree in any normal fluid dynamic scenario thru a simple smooth-bore pipe, but I think your ignoring one thing: Cavitation.

 

When coolant is allowed to flow too rapidly, (too much flow) thru the small convoluted water passages within a radiator, the fluid cavitates severely within the passages of the radiator and heat transfer efficiency is LOST, not gained.

 

I'm no expert either, but I have heard for years that a smooth, controlled flow of coolant (thru the radiator) is much more efficient, and provides more cooling, than a rapid, uncontrolled flow of coolant, due to this cavitation.

 

You are absolutely correct about the concept of cavitation and how it would affect the cooling capacity. The unknown part for me is if cavitation would actually happen inside a radiator. I do not believe so. Since the speed of the water pump does not change, there is actually a fairly small difference in water flow through the area where the thermostat is mounted if it is removed (compared to a wide-open thermostat, of course). I believe cavitation is a relatively high-speed phenomenon in a completely submerged environment (no air), and I doubt seriously it would actually occur in a radiator.

Goose

[wes0778]

Don is exactly correct - the engine must operate within a specific design range for lowest pollution, best fuel economy, and longest life. The thermostat lets it heat up to that range the fastest, then keeps it in that range under different outside conditions.

 

The engine life issue is because all metals expand at different rates and by different amounts. When the engine is designed, they have to select clearances between the various parts that will allow it to run when started cold, keep running when one metal, such as an aluminum piston, expands faster than the metal it is near (such as a steel cylinder wall), and still maintain all the acceptable clearances after all metals have completely heated and expanded to their maximum size.

 

Goose

 

Yup, would you believe the pistons for some engines are machines oval shaped, so that they end up round when the engine reaches "operating" temperature.

 

Also as for heat transfer, the law of diminishing return comes in to play. When the speed at which a fluid passes over a surface reaches a certain point, it is moving too fast to absorb heat from that surface.

Kinda the same situation as picking up a hot baked potato. Grab it and hold on to it and you will experience heat transfer. But if you bounce it up and down in your hand, it is touching you too fast for heat to transfer to your hand.

[Guest tx2sturgis]

I believe cavitation is a relatively high-speed phenomenon in a completely submerged environment (no air), and I doubt seriously it would actually occur in a radiator.

Goose

 

I could be using the term incorrectly, maybe its called aeration, but what I'm referring to is the air and vapor bubbles that are trapped in the coolant system and washed thru the radiator if the flow is too fast....causing efficiency to drop off.

 

 

 

Edited July 8, 2010 by tx2sturgis

[wes0778]

. Since the speed of the water pump does not change, there is actually a fairly small difference in water flow through the area where the thermostat is mounted if it is removed (compared to a wide-open thermostat, of course). Goose

 

 

Actually since most, if not all, vehicle water pumps are of the "non-positive displacement" type, flow can vary widely, depending on the restriction encountered. The thermostat acts as a variable orifice (read restriction) which controls the volume of coolant flowing to the radiator.

[V7Goose]

Yup, would you believe the pistons for some engines are machines oval shaped, so that they end up round when the engine reaches "operating" temperature.

 

Also as for heat transfer, the law of diminishing return comes in to play. When the speed at which a fluid passes over a surface reaches a certain point, it is moving too fast to absorb heat from that surface.

Kinda the same situation as picking up a hot baked potato. Grab it and hold on to it and you will experience heat transfer. But if you bounce it up and down in your hand, it is touching you too fast for heat to transfer to your hand.

This is not an accurate representation of heat transfer. It is never moving too fast to pick up heat, but if the duration of contact is short, it only picks up a little heat - the longer the contact, the more heat.

 

Think of a hot griddle as the hot water in your radiator. The entire surface is equally hot,a nd if you were to just briefly tap it with one finger, it would be like your potato - you might feel a slight warmth, but nothing real hot. Now swing your arm so that your finger slides very rapidly from one side of the griddle to the other - each individual point of contact in that arc is probably even briefer than the quick tap you tried first, but your finger remains in contact for the entire distance. I'm pretty darn certain you will be yelping before your finger gets to the other side! For heat transfer, it is the DURATION of the contact (along with the relative temperature difference), not the speed of the motion that affects how much heat you pick up. Since the radiator is in contact with the hot coolant 100% of the time, it is transferring the maximum heat possible (based on the relative temperature differences) 100% of the time. The reason a fan makes it cool more is because the air flow is moving the heat away from the radiating surface, thereby reducing the relative temperature on one side.

 

I could be using the term incorrectly, but what I'm referring to is the air and vapor bubbles that are trapped in the coolant system and washed thru the radiator if the flow is too fast....causing efficiency to drop off.

Your term is slightly off, but the concept is mostly correct. This is exactly why I mentioned cavitation in the absence of air. The same priciple applies to a boat propeller. If the propeller blades break the surface of the water, they pick up lots of air from the splashing, thus causing interruption to the smooth flow around the blades at even low speeds. But if the propeller is completely submerged, it must turn MUCH faster before the friction and flow currents around the blades begin to form the vacuum that is the source of cavitation (they form their own bubbles directly from the water).

 

If your cooling system is properly filled and has a functioning overflow tank, there should be no air inside, thus there is no splashing and air bubbles to interfere with the heat transfer.

Goose

[V7Goose]

Actually since most, if not all, vehicle water pumps are of the "non-positive displacement" type, flow can vary widely, depending on the restriction encountered. The thermostat acts as a variable orifice (read restriction) which controls the volume of coolant flowing to the radiator.

Yes, your statement does not disagree with me at all. We all understand that a closed, or even partially closed thermostat causes a big difference in fluid flow. But my comment specifically compared it to a wide open thermostat. While I have never measured the actual flow difference, it is my belief that at the low flow pressure generated by a "non-positive displacement" pump, there is actually a fairly small difference in GPM between a fully open thermostat or no thermostat at all.

 

To me, however, the flow rate with or without a thermostat is simply an interesting academic point to debate since there is absolutely no positive benefit to be gained by actually removing it! That's why I am just sticking with my opinion here instead of actually doing the research needed to prove or disprove my point.

Goose

[twigg]

The thermostat turns a passive system into a positive feedback system that is able to respond to environmental conditions, and engine work.

 

If there were no thermostat, the engine would warm up to correct temperature very slowly, because it would have to heat all the fluid in the system at the same time as the rad is trying to cool it.

 

In warm climates that would increase wear, and in cold climates it would probably never heat up unless you were stuck in traffic.

 

The thermostat "begins" to open at a set temp, and is only "fully" open much hotter. This means that it restricts the flow sufficiently to keep the engine at the correct temperature all the while the system is heating, and crucially, it can close again if it senses that the coolant is cooling too much.

 

The whole system is pressurised to help it work more efficiently so ...

 

If the thermostat sticks closed, you are in trouble. The small amount of coolant in the engine will rapidly heat and you will get little or no warning before it overheats and seizes, unless there is a secondary "engine temp" warning on the engine side of the system.

 

If it sticks open, or you remove it, then your engine will warm up slowly, may never warm in some places and you will be running way out of peak efficiency ..... increased wear, etc.

 

In very cold weather it is possible that the cooling provided by the radiator can overcome the ability of the thermostat to regulate it, that is why you sometimes see part of the radiator blanked off in winter.

 

Hope this helps.