I am noticing a problem with my bike after I have been on longer rides (> 30 miles). Short distances I have no problems. And on the longer rides I don't have any problems until I start getting into stop and go type of conditions which usually is at the end of my rides.
The temperature gage stays pretty steady around the little white thermometer. But as soon as I hit regular street traffic and lights, it will start inching towards the red zone. Several times, I am left with fluid spewing out of the overflow hose after stopping.
The fan kicks on after riding and I can hear the air flow. But I don't know if it every kicks on (or even if it is supposed to) when I am riding and it starts getting that hot.
Right now the only thing I can think of trying is flushing the coolant system.
Anyone ever do this? Any other hints or clues?

Thanks :)

Here are the things it could be in rough order of liklihood for troubleshooting:


1. Low coolant level.

2. Bad thermostat. Drop it in boiling water and see if it opens. Push on it and see if feels sticky. Is it corroded?

3. Thermal switch not working at correct temperature or intermittent fan operation.
Somehow you are going to need to check this. Also, make sure the fan is working at full power. Idle the bike until the fan cycles on and off. Use an ammeter to check the fan.

4. Clogged radiator or coolant passages.
Flush out your engine and radiator. You could have the radiator flow tested at a radiator shop. Radiator flushing products can make the problem worse-- they can dislodge particles which then clog up the passages worse. Remove the radiator and backflush. Flush out coolant pasages into engine.

5. Water pump impeller corroded or broken.

6. Piston rings worn out or other internal engine problem-- cam timing chain slipped. Ignition timing.


7. Head gasket leak (not likely.)

8. Low oil level (even less likely.)


Good Luck

Mike...My fan comes on only when the indicator is right at the thermometer, usually idling at a light etc. I think it should come on well before the red zone. I'm guessing it's not as hot up there as it has been in mid-Ohio here lately (mid to upper 90s), and my temp guage never gets to the thermometer while I'm moving. Yours sounds a little high, so my vote is a bad thermostat or clogged radiator/water passages as KD says above. Since you say your fan comes on after a ride, I would note where the temp guage is when you hear it. If it is much past midway, I would...
Drain/flush the system
Remove the radiator and back flush
Install new coolant
Go for a ride....note the temp guage. Hopefully you will have 'flushed' your problem...
Check the thermostat as KD suggests

Even if the thermostat checks out ok, you may still want to replace it. Sometimes they work sporatically when they get on in age.

Thanks for your suggestions.

1. Low coolant level.
}This is only a problem when most of the fluid has gone through the over flow

2. Bad thermostat. Drop it in boiling water and see if it opens. Push on it and see if feels sticky. Is it corroded?
}I plan on checking this when I flush.

3. Thermal switch not working at correct temperature or intermittent fan operation.
Somehow you are going to need to check this. Also, make sure the fan is working at full power. Idle the bike until the fan cycles on and off. Use an ammeter to check the fan.
}The only time I notice my fan going on is when the bike has been shut down after a longish ride. Never while at idle or while riding, that I can tell.

4. Clogged radiator or coolant passages.
Flush out your engine and radiator. You could have the radiator flow tested at a radiator shop. Radiator flushing products can make the problem worse-- they can dislodge particles which then clog up the passages worse. Remove the radiator and backflush. Flush out coolant pasages into engine.
} I am going to try regular flushing first. If I have to check the fan, I will backflush it.

5. Water pump impeller corroded or broken.
}I sure hope not. I will try to run the bike with the cap off, if I get flow I am going to assume the impeller is okay.

6. Piston rings worn out or other internal engine problem-- cam timing chain slipped. Ignition timing.
} Not having any performance issues, just got a new IC Ignitor.

7. Head gasket leak (not likely.)
} No fluid leaks except from the overflow hose.

8. Low oil level (even less likely.)
} Oil was fine before I changed and fine now.

Mike...My fan comes on only when the indicator is right at the thermometer, usually idling at a light etc. I think it should come on well before the red zone. I'm guessing it's not as hot up there as it has been in mid-Ohio here lately (mid to upper 90s), and my temp guage never gets to the thermometer while I'm moving. Yours sounds a little high, so my vote is a bad thermostat or clogged radiator/water passages as KD says above. Since you say your fan comes on after a ride, I would note where the temp guage is when you hear it. If it is much past midway, I would...
Drain/flush the system
Remove the radiator and back flush
Install new coolant
Go for a ride....note the temp guage. Hopefully you will have 'flushed' your problem...
Check the thermostat as KD suggests

I didn't have this problem all winter. But then I was riding in temps 60 and below. This all started when the outdoor temperatures started going over 70. Looks like I will have to break out the service manual and do what you and KD suggest.

Thanks

Even if the thermostat checks out ok, you may still want to replace it. Sometimes they work sporatically when they get on in age.
I will try that if I am still having problem after checking everything else out. The one thermostat I am suspicious of right now is the one for the fan. I may replace that outright. Now were did I put that manual.

Thanks

I wanted to report back my results.

Last Friday, I did the full flush. This requires draining and filling your cooling system 5 times. Once to empty old coolant and put the flush compound in, three times to rinse out the system and finally to fill it back up with fresh coolant.

I am really glad I did it. After the first run with the flush compound, there was so much crud in the crankcase, that I had to get a piece of wire to poke through it to get the crankcase to start draining fluid. Don't want stuff like that flowing through your system.

It seems the biggest problem was a bad radiator cap. I went on two hundred mile rides over the weekend and no problems with the overflow line expelling any coolant. Only once did the engine seem to be running hot and that was in bumper to bumper traffic I got stuck on from an accident back up on the freeway.

I am going to keep monitoring the tempurature. With the one problem solved, I am a little suspicious of the tempurature regulator. I may pull it and test it if I still have problems with the temp dial on the dash. But unless that becomes a regular problem, I am considering this job done.

Mike, Thanks for the update.. lots of times we don't hear the end results.. glad to know you may have solved most of the problems with the flush.

I was going to mention radiator cap. That's one commonly overlooked item and it can cause a pain. Glad to hear that you got it flushed. I flushed mine when I brought her home, thankfully no crud.


I wanted to report back my results.


It seems the biggest problem was a bad radiator cap. I went on two hundred mile rides over the weekend and no problems with the overflow line expelling any coolant. Only once did the engine seem to be running hot and that was in bumper to bumper traffic I got stuck on from an accident back up on the freeway.

Mike,
I have the exact same problem with my 96 Vulcan.
I'm glad that you got the problem resolve. I will try to do likewise.
http://www.vn750.com/forum/images/smilie/icon_smile.gif
Thanks