I have a 2002 R6 that seems to be having a cooling issue. I recently moved from Oregon to the Phoenix area of Arizona and I knew I would have cooling problems, but I think this is a little odd. I changed out my coolant from normal antifreeze to Cyclelogic's Engine Ice and it has definitely made a big improvement, but I'm still having issues that my brain tells me shouldn't happen.

Here's the problem. My temperature runs, according to my gauge, within normal operational range. According to the Yamaha Service shop, the cooling fan shouldn't kick in until 225 degrees. Before I even get to 225 degrees, mostly from 212 and above, I start to lose coolant out onto the ground. Not nearly as much as I did with normal antifreeze compared to the Engine Ice, but I still lose some. My fluid levels are where the manufacturer says they should be, full radiator, and the overflow tank between low and full. The fluid is coming from a tube behind the fairing, about midline on the left side, not the tube that hangs down right next to the overflow tank.

Why am I losing fluid before the fan even kicks on, and before the book or the engine light says I'm overheating? The dealer says I must have a cooling problem, but I'm not going to pay them money to try to figure it out just yet.

Has anyone had this problem before and what did they do about it? Is there a different thermostat that I can install in it? Would it be wise to install a switch on the fan so I can turn it on manually? Or do I really have a flow problem? Is this tube supposed to be hooked up to something, like the overflow tank? All the tubes seem to be in order, so it seems strange that this one would leak coolant. Or is there a larger radiator that I can swap out for the dinky stock one?

Any knowledge on this issue would be greatly appreciated!

I think I know more of what is happening with this problem, but I still don't understand why. I pulled my lower fairing and traced the hose I'm losing the fluids from. Lo and behold, it is the overflow hose on the overflow tank that I'm losing my coolant from.

So here's my theory, and this would account for the "bubbling" or "boiling" sound I heard today when I was stopped and shut down after a slow stop and go ride.

The fluid is getting hot enough, even before the engine temp says it's overheating, that is is expanding to the point, the system dumps fluid into the overflow tank, which in turn becomes full and overflows out onto the ground. Why, is what I want to know, and why it's happening when I'm technically not overheating! Is the manufacturers recommendation of keeping the overflow tank full, or near full, too much fluid in the system for a hot environment?

There could be a couple things....if it has a hard time cooling down until like last min there might be a problem with your themostat. If it doesnt and you say you are leaking from behind the fairing, well you have a leak issue with the line that goes behind it that feeds up front. Check to see if the line is cut or not plugged in all the way. Also make sure is isnt coming from anything else like on the block and etc. There is a possibility there is now air in the system, you will need to run it for a while and monitor it and then top off the fluid. if you dont use a pump sometimes to force the coolant into the system, then there is probally still air in there somewhere. hope that helps

I think it might be the thermostat because after examination I have no leaks anywhere but with the overflow tank's overflow hose. I'm thinking that the thermostat must not be working properly causing fluid to fill the overflow tank, because it's not circulating properly, thus it overflows onto the ground once it becomes full.

The last time I checked my fluid level in my radiator it was good, but I will check it again. When I replaced my fluid, I poured in the proper amount according to the manual, so I don't think I have any air pocket problems, but I will dig into that one more too.

Thanks for your thoughts!

Anyone know the temperature that the thermostat is supposed to open at on this bike?

By the way, I checked the fluid levels, it's where it is supposed to be.

NT...it cools down ok...when stopped at a light, then I get moving again it comes right down. Even when I park it and watch the temp after it has been shut down, it continues to climb anywhere from 6-10 degrees before it starts it's trip down, so it's not like the coolant isn't working, it just overflows on me before it even gets close to overheating. Strange....

sounds like you just got too much coolant in there to be honest with you, the thermostat needs to reach a certian temp to open up, and a certian pressure to push new stuff in there as well. If it works the way a car works, the fluid on the top of the radeiator will push the cooler stuff up the hose on the bottom of the radeiator and into the thermostat, when the inner parts of the thermostat reaches a pressure and temp it will open let new cooler coolant in and push the old stuff out and back into the radeiator to be hit by cool flowing air and cool it down. and it just keeps cycling. try draining a little fluid into a clean cup or something, see if that corrects your problem...but save it so if that isnt it you can at least put it back in instead of buying more

Okay the thermostat doesn't need any pressure to work. This is why you can test them by dropping the in a cup of hot water.

It sounds like your stat either isn't opening at the right temp, or is faulty through some other means. I think the stat is a 180, but I could be wrong.

If you have an electric multi-meter you can check to make sure the temp sender is working correctly. You should have 50-64 ohms of resistance at 176, and 16-17 ohms at 248. (Although you won't be able to test you high temp figures)

Also, you might want to drain and refill the coolant. I know it's a PITA, But when I worked at an auto-garage during college, we would get overheating problems from people who would flush their cars and then get an airpocket trapped in the system. Air does horrible things when you're trying to run a liquid cooling system.

I'm not sure I have an air pocket because the problem is still there even though I have replaced the coolant, though it is not as bad with the Engine Ice as it was with normal coolant. I also was able to put in the amount of coolant that the manual says the system holds. If I hadn't, I would suspect an air pocket, but seeing that the problem is the same, just the amount of fluid I lose is less now from the coolant change, I think it must be something else such as the thermostat. Which today, I heard a boiling sound in my system today, yet the temp guage was still showing operational temperatures.

I talked to a mechanic friend of mine, unfortunately not a motorcycle one, but hey, one's better than none!

He seems to believe from my description of things that I have an airflow problem, not necessarily a thermostat problem, but that's just an educated guess without actually being able to observe the problem.

Anyway, I'm still open to ideas, because I'm not sure what I can do in regards to an airflow problem unless I can lower the temperature that the cooling fan kicks on?

check the air box, make sure thats clean and unblocked, blow the radeiator with an air line clean any dirt out of there, go with that for now, cleaner the better

Here's the thing with airflow, and NT it would be airflow through the rad not into the airbox, Air flow will allow you bike to cool more efficiently when you're moving.

But the problem you have is that your cooling system is running at a severe range of temperatures. Not very hot be the sensors, and superhot in the rad. I would lean toward either a bad thermostat, some sort of clogged passageway or some other motor problem that is preventing even circulation of coolant. You are developing hotspots in the motor which isn't good.

The flow problem with the fluid seems more logical than with the air flow through the radiator. My mechanic friend did mention that a thermostat not opening all the way could be the cause of it too. I guess the only way I'm going to find out is to break down and purchase a thermostat and start there, plus do a vineger and water rinse out before I put the coolant back in.

Does anyone know if they make a thermostat for hot weather areas? It gets warm enough in Phoenix that my bike upon start-up is already in operational temperatures.

I know they do for cars, im sure they do for bikes too. Just a low level or low temp thermostat. Cars and trucks that are suppost to be between 190 - 210 can get them for like 165 degrees i think. Downside is that your heat in the winter sucks, and takes the car or truck longer to warm up. People like me in Ct get screwed. 85 - 100 in the summer, and -10 - 30 in the winter

I don't think I will have that problem in Phoenix. Yesterday I started my bike up cold around 5 pm in the afternoon for the first time, thought I would need the choke...it wouldn't start...so I shut it off...and it fired right up....as soon as the temp gauge came on the bike was already 105 degrees....Hmm...it was currently 105 degrees ambient temperature right then that day. Yeah it gets cooler in the winter here, but only down in the 40's at night 70's during the day.