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Discussion Starter #1
I have a 2004 vulcan 750.The bike runs great and cool when you are going down the road.Soon as you come to a couple of stop lights it heats up and the fan kicks on pretty quick,even in cool wheatherIt never used to do that,does anyone have any addvice for me,Thanks Tom
 

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I've also read that if the coolant is more than a 50/50 mix, it lacks some cooling potential.
 

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1985 VN-700
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Mine does the same thing. I installed a new thermostat thinking that was it. No difference. Im thinking either radiator need to be cleaned, or temp sender off and it really isnt that hot.
 

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Linkmeister Supreme
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The temperature gauge sending unit operates totally separate from the coolant fan switch, so if the gauge needle rises and the fan comes on they are both working as they should.

Is there any coolant in the overflow tank?
Is the rest of the cooling system full?

The temp gauge rising also indicates that the thermostat is opening and letting some coolant circulate to the radiator. There may be enough coolant to submerge the temp sending unit and fan switch mounted low on the (edit: left side of the) radiator, but not enough to fill the rad core and cool it efficiently.

(Edit, Mar24: Correction- The temp gauge sending unit is under the tank on the thermostat housing, not on the rad.)

`86 has a point too. Antifreeze is most efficient at a 50/50 mix with distilled water.
If straight antifreeze is installed in the cooling system it may act like these symptoms.???
Don`t know for sure as I have never seen it done or heard of it done before.
Check specific gravity of the coolant in the system to determine strength of mixture.

As L2fish says, it is also possible the rad is plugged. If the end tanks can be removed from the core, it may need to be rodded out at a repair shop.

That`s all I can think of now.
 

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Straight anti freeze will run hotter than the 50/50 mix. It doesn't have the cooling capabilities of the mix. Usually with it heating up that quickly at a stop is an indication that the coolant level is low. It is the same way in a car.
Does it cool back down when you get to moving again? If it does is it cooling down fairly fast? Or cooling a little slower?
 

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If you are out of the freezing temp time where you are, drain and flush your cooling system. Then fill with distilled water & Redline water wetter(or similar). Has all the properties needed for cooling system, is aluminum safe, and transfers 50% more heat to the air than water/AF mix.

The 750 needs lots of moving air to work, slow riding or frequent stops do not bode well with it.

Jon
 

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Down here in the desert I ride in a lot in high winds. I have noticed that when riding with a heavy tail wind (30+) my temp goes up quite a bit after about 10+ miles. When I turn crossways to the wind the temp comes back down. Gotta have that flow across the radiator I guess.
 

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Discussion Starter #9
It cools down when you get moving but not very fast.Do youknow what the sensor at the bottom left side of the radiator does?I know the top sensor by the thermostat is for the fan.I wonder if the bottom sensor has something to do with the temp problem.What do you think?
 

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Linkmeister Supreme
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It cools down when you get moving but not very fast.Do youknow what the sensor at the bottom left side of the radiator does?I know the top sensor by the thermostat is for the fan.I wonder if the bottom sensor has something to do with the temp problem.What do you think?
The sensor on the lower left side of the rad is the cooling fan switch.
The sensor on the thermostat housing is the sending unit for the temp gauge on the dash.
 

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This being an '04 model, seems extreme to be addressing the sensors as the potential source of a coolant problem. What about the basics?

  • What is the coolant level?
  • When was the last coolant changed/flushed?
  • Has the coolant system been bleed?
  • Is the thermostat working properly?
  • etc.
 

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1985 VN-700
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On my 85 700 mine will run right up to the last notch before hot in only a 30 minute ride in stop and go traffic. I have changed the thermostat, flushed and change the coolant, bled the air out of the system as you are supposed to. Now, the funny thing is that the fan turns on after I shut the bike off, and it isnt overheating, so my brother in law thinks the sending unit is sending false signals. He has an infared thermometer but I havent had the time to stop by his garage. Another thing I might do is add a switch to turn the fan on manually when im in traffic.
 

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My bike's fan turns on with the ignition. It was still having some overheating issues before the weather got cool though... I'll probably have to deal with it this summer, but right now it doesn't overheat at all.

Summers here go up to 120+, so... for normal people, having the fan on with the ignition might keep it cool all the time.
 

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I've had the fan come on a few times in warm weather after turning the engine off. I assumed it was normal.
 

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Heading to the DARKSIDE!
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Yes......I second the idea of distilled water and redline water wetter(doing this REALLY works)!.....and maybe a small amount of straight green antifreeze just in case you live in an area where the temp gets a little below freezing(if your not located in an area like that, leave the green antifreeze out). Make sure your thermostat is working properly and is clean...also that your wire connections on the fan motor, fan sensor and temp gauge are good and working well. Check for proper seating,gasket condition and spring tension of the radiator cap. Check overflow tank for clogged rubber hose and also for a cracked tank letting coolant out. Take out the fan sensor and temp sensor and clean the tips with scotch brite/steel wool. They get crusty on the end and can cause false readings. Make sure your cooling system is at the proper coolant mix level and is clean and free flowing. Two other tips that I have performed is.... along with flushing the inside of the radiator make sure you flush out all dirt and bugs from in between all the cooling fins(they get pretty dirty)! The other major tip is to upgrade the plastic OEM fan blade to the Muzzy's Performance Aluminum fan blade(model # HT-H5). I have done this and it really is alot lighter and moves twice as much air through the radiator....effectively cooling the radiator much better. Hopefully this can help all who are redoing there coolant system.:smiley_th
 

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Find an A/C man. My best friend was an A/C man. They use a coil cleaner for the evap coils. You squirt it on in liquid form, it turns into an exoanding foam and pushes all the crap out of the small spaces. Then you spray it off with the hose, easy. We used to do a lot of off road 4wheeling with snorkels in 6 feet of water. After every trip you had to clean your bike right away. If you didnt, well have fun. Thats when we used this stuff. My buddy said you probably should not use it more than a couple times cause its not good for the metal, but I promise you there is not a better or easier way to clean it.
 
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