Yikes, thermal light for first time

I am hoping you WR experts can give me some advice here. I have a 2012 Wr250R that had been basically troublefree. I luckily live in the Mountains of New Mexico and the weather has got nice enough that I have started riding trails.

Today, for the first time ever I got multiple  high Temp light events. I would shut off the engine for a minute or two, then restart. I would get several minutes of riding, but then it would light off again. It occurred for various range of engine operation including just cruising along at low RPM  and climbing in a low gear like 2nd at higher rpm.

The only thing different from my previous configuration is an oil and filter change with full synth oil and a K&N filter, adding a IMS 3.1g gas tank, and topping off the radiator reservoir with Subaru premixed coolant. BTW, I did note that the cooling fan was operating.

I am trying to avoid going to the dealer who is pretty far away. Would you suggest a full drain and coolant replacement? Can I use standard premixed DEXCOOL (which I have a lot of, says it is good for aluminum radiators). Any other thoughts about what might be causing this and what actions I can take?

I checked for leaks and did not find any. The overflow reservoir was filled to between the low and high lines. I did not check inside the actual radiator yet as it was hot.

I have run the bike for hundreds of miles of trails in the past with no cooling issues.

I really appreciate any helpful comments you experts might have to give me some strategy for moving forward.

Mark

First did you hear your fan running, and second when you changed the tank you might have got an air lock when adding the 50-50 mix of antifreeze.

Yes, I did hear the fan running.

I will see that I ran the bike several times after the new tank install with new thermal light.

Do you think that perhaps the Subaru coolant was not compatible with the original coolant?

Is the fan spinning or just making noise like it is?

I had the fan blade get striped from a tip over that jammed it then the bike over heated the next slow trail ride, it sounded like it was working but the fan blade wasn't turning.

Its possible the coolant wont mix with the stock coolant, it should say so on the back of the jug.
If you have lots of Subaru coolant drain the mixed stuff from the bike and fill it with nothing but Subaru coolant.

As the previous guys stated chase the fan first but beyond that I would remove the premixed subaru coolant.  Its not garbage but it formulated with additives to address a leaking issue common in subarus engines.  I would go with a decent coolant for bikes and then add in some water wetter or cool-aide (maxima product) as prescribed on the bottle and no more than recommended. The WW or CA raise the boiling temps of the coolant and reduce the surface tension so that there are a reduced number of tiny air bubbles formed against the inner walls of the radiator and give direct access to the fins to transfer the heat out more effectively.  Be careful though as they reduce the freezing resistance of the coolant  The WR is a hot running little thing that isn't helped by stock fueling maps.  If you have any mods the little cooker gets super hot as its already pretty lean stock.  Running a proper map without the "emissions" tuning will help cool the engine as well as give it a little kick in pants power wise

you stated that you changed the oil. Did you open the oil flow plug and see if you were getting oil flow? This is the only thing I could think of not mentioned.

Thanks much all. I think I will replace the coolant. Might get a fuel controller as well.

Can you suggest a proper coolant for this bike (something I can get at an Autozone place. I am kind of in the middle of nowhere.

I did not check the oil flow plug. I can check that as well. Mostly I heard most people don't do that, so I did not at first.

Oh, do you think I need to flush it with distilled water first prior to replacing with a good bike coolant mixture?

I wouldn't worry too much about the coolant brand or flushing with distilled water. Any normal brand premixed should be fine, just make sure its aluminum safe. Highly recommend getting some of the water wetter or Cool-aide though.

Thanks for all the advice folks. Turns out it was a pinhole leak in the coolant hose going to the water pump. It was leaking into my scuff plate where I could not see it. $.75 later, some new fluid, and all is well!