What would you do- random overheat

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Bill Lumberg

Merica
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Nothing alarming, but after a long stretch with zero issues, Ive had a few Hi temp situations on my 14. April 1, 3am at my first Tour of Honor site, I left the bike running for two minutes at just over freezing while I got my shot. Got on the bike and pulled across the street to plot nav, and I saw it switch from a number to Hi. Shut it off for 3 minutes while I fiddled with the gps, and no further issues for the rest of that TOH SS1K or any day after.... Until today. 75F. Heavy traffic. Almost 30 minutes with very little movement. Bike went to Hi twice. Both times I killed it and pulled to the shoulder immediately, letting the fan run for a bit. No further issues. Coolant is fresh (from last year) and at the proper level. Im not alarmed, but I am a bit puzzled, as I normally deal with much hotter conditions and traffic without seeing this. This is after a year, including a full southern summer, with no heat issues whatsoever. I dont know what to check. Your input is appreciated.

 
Make sure the radiator cap is on tight! You may think it is full based upon the level in the overflow tank but if the cap isn't secure, it won't suck liquid back into the radiator as it cools - might be only half full.

Other than that, I would verify that the thermostat is OK and opening/closing when it should.

Kinked or collapsed line somewhere is a (slight) possibility.

We will assume that the water pump is working...

 
I wonder how similar your situation could be to one I used to have on a car about 20 years ago. I checked the coolant levels a few times, but kept finding this car would give no interior heat in the winter, yet the engine was in the high temp zone - in our Canadian winter. Turned out there was some slow leak in the coolant circuit, and it seemed just at the threshold where the mechanical thermostat should have "popped" - but must not have been, I had the thermostat out and tested it in a pail of hot water etc - but it wasn't the root cause. Parked outside, I didn't really observe a pool of leaked coolant, but sure enough, after I replaced rad hoses top and bottom, then re-established levels, the problem never returned.

 
If you haven't yet, pull the panel and check the radiator itself not just the overflow as we sometimes just depend on the tank being accurate and working right. Other than that it might be thermostat change out time.

Let us know what you find.

Dwayne

 
I already have a replacement radiator cap that I bought as a precaution with my previous overheat issue. Ill put that on today. I need to look up where the thermostat is. Ill probabably have that replaced as a precautionary measure.

 
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If you are going to replace the thermostat, to get to it, you will be at well over 75% of the labor and effort to check your valves. You might consider doing both at the same time.

 
Thermostat is right below the radiator cap in the same housing. If you're changing the cap, drain the coolant and with a little more digging you're done.

--G

Edit to add the other piece of the parts puzzle...

 
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I already changed the cap. Bike is running a little hot in general. Yesterday, I started a cool bike and watched as the temp climbed to 230 over maybe four minutes. Fans came on, and temp stoped at 233 but never went down. Cooled the bike and repeated with same results. Given how slow Y.E.S. was on my last problem, I may just pay to have a new thermostat put in rather than losing weeks or months of riding time. Valves were done in February. :)

 
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I assume that the radiator is really topped up - not just based upon what is visible in the expansion tank?

If the line from the expansion tank is blocked or kinked, liquid won't go to or from the tank.

If there is a hole or crack in that hose, liquid will go out of a hot radiator into the tank (with minimal leakage) but when the radiator cools, the liquid in the expansion tank won't suck back into the radiator. Same if the hose that goes to the bottom of the tank is missing, degraded or curled around so the open end of the hose is above the liquid level.

Does anyone have any idea what is the opening temperature for the thermostat?

 
If this problem started after the valves were done it might be related to that work. The tech may not have purged all the air from the cooling system after he put it back together.

 
This is when I think of past air conditioning work, maybe solder in a 1/4" access valve to the coolant pipe just to vent the air at the highest point. Or, if you could find a large enough one, even the clamp-on style would do fine. Maybe just add a tee: temp sensor one way & a little vent petcock another way.

Of course another option is to turn the bike over and use what is normally the coolant drain plug as the vent. From what I understand radiator caps, thermostats and cooling fans are not position-dependent. JS.

 
Does anyone have any idea what is the opening temperature for the thermostat?
From the FSM: Opening temperature 69 - 73C, full open 85C

--G
OK, 185 °F, thanks.Well below the temperature observed by Bill. I still think he issue is more likely associated with the radiator being not filled completely due to one of the reasons I suggested, above; especially since he confirmed that the radiator cap was replaced (and assumed to be tightly secured).

 
Radiator is full to the top. Bike is still rideable. I just keep an eye on it if stopped for long. Great input from all. I very reluctantly decided it was not smart to take it to the coast on my upcoming trip. I am concerned that a thermostat that (is suspected) to be operating out of spec may be at a greater risk for failure. I'd rather that happen near home. My goal is to have it swapped out the day after I return.

 
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How's the radiator look? You ride a lot and perhaps that Georgia clay is caked into the fins? I had a couple overheat incidents last year and found the radiator plugged with lots of crud. Soaked the fins in Hydrogen Peroxide, use a pick to clean out some debris and back flushed it with water and compressed air. No problems since.

 
It looks clean and undamaged. Very good for a mile with this mileage. I need to backflush when I get back as a precaution. Given that the first symptom was in the predawn hours of 1 April, it would seem that I did a SS1K and a few more weeks of riding while it was in this condition. So its a subtle thing as long as I watch it. Will advise when Im back home and the thermostat is replaced.

 
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