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I've got a Gen 2 (2012) with about 80K on the clock. In 4th or 5th gear at speed everything's fine. My temp gauge reads 4 or 5 bars out of 10. When I slow down in traffic or around town it moves up pretty quickly to 6 or 7 bars. Not catastrophic but it's going in the wrong direction and summer's coming. I'm going to try hydrogen peroxide on the fins along with compressed air from the back and as much water pressure as I can get from the garden hose. Coolant level is good and (reasonably) fresh. Fans come on around 6 bars and sound good. I only bring it up because it's been getting worse over the last 10K miles or so. It's also noticeably different from my previous (and basically identical) '06.

My question is, does the "good reading" at speed make it more or less likely to be the thermostat or water pump or radiator flow/blockage? I'm wondering what to try next.

Thanks as always.

When was the last time the coolant was changed and what was used?

Season before last? 50/50 premix. I don't remember the brand - picked it up from Iron Pony. Probably the same stuff I've used for the last 180K on FJRs.

Make sure the radiator is topped off completely and that coolant siphons back from the overflow tank as the bike cools. A kink or leak in that hose could keep the radiator from being full even though there is coolant in the tank. Not sure where the temperature sensor is but it is possible that the "true" coolant temperature is not being read if the radiator is not full.

Also, be very careful with water pressure at the radiator - fins bend easily.

I'll check the return hose and the level under the cap but is that something that could come on slowly over time? I'd expect that to have happened at a coolant change or some other event.

FJRoss wrote: ↑Thu Mar 25, 2021 9:16 am Also, be very careful with water pressure at the radiator - fins bend easily.

Will do thanks. I'm a little concerned about compressed air too so I'll take it easy.

FjrVfr wrote: ↑Thu Mar 25, 2021 8:46 amI'm going to try hydrogen peroxide on the fins along with compressed air from the back and as much water pressure as I can get from the garden hose.

FjrVfr,

Hydrogen peroxide is good for dissolving bugs and other organics.

The radiator fins on the FJR are very delicate. A strong stream of water from a garden hose with a nozzle can bend the fins over, and if you bend them back, they will (very likely) snap off. Same goes for compressed air. A generous gentle flow of water from an open hose should be okay, just take your time, let it soak in awhile, and repeat as needed. I suggest that you research the selling price of a new radiator first, before you get going on it.

If I saw my FJR overheating, I would first replace the coolant (and I would use the Yamaha magic stuff), and then maybe the thermostat. There is a coolant drain bolt that will help with the draining. It is the bottom bolt on the water pump cover, the one with a copper gasket. You might want to get new copper gaskets on hand, to start. You can even do a flush/fill with clean water, before draining the water and the final refilling with coolant. Since the coolant goes long, I just ignore the price on the Yamaha stuff. A gallon will do the job.

My US$.02 worth . . .

Over time, I've noticed a similar trend with my '09. It's never maxed out the temp gauge, but does have a tendency to elevate when stuck in traffic or stop and go; it quickly drops once back up to speed. Fans cycle on as normal, and do push the temp gauge down when they do.

FjrVfr wrote: ↑Thu Mar 25, 2021 9:39 am I'll check the return hose and the level under the cap but is that something that could come on slowly over time? I'd expect that to have happened at a coolant change or some other event.

FJRoss wrote: ↑Thu Mar 25, 2021 9:16 am Also, be very careful with water pressure at the radiator - fins bend easily.

Will do thanks. I'm a little concerned about compressed air too so I'll take it easy.

It could come on slowly. Radiator might start out full and when the engine gets hot, coolant is pushed into the overflow tank. When the engine cools, you might be getting all, most, some or none of that coolant going back to the radiator. Incomplete return along with (minor) evaporative losses might lead to a chronically underfilled radiator.

The thermostat is obviously working as the temperature is coming down at highway speed but it may not be opening completely. Same with the water pump - working but possibly not efficiently. Higher speeds mean more flow of cooling air over the radiator and better flow of coolant through the system. (I doubt that a dirty radiator is the root cause.) Also, coolant doesn't really go "bad" - it will always remain a good heat exchange medium and will continue to protect against freezing. It needs replacement because the anti-corrosion compounds get depleted and the fluid becomes contaminated over time.

Not as much of a problem as it used to be but if you have deposits building up in the radiator, it will lose efficiency. This can happen if you "top off" using hard water rather then demineralized. Also happened due to incompatibility in the early days of OAT (organic acid (additive) technology) coolants. A radiator chemical flush might help but might damage the radiator - they are made with pretty thin metal.

When my ‘14 had a problem, it would only happen sitting. At speed it was a little warmer than normal, but far from overheating. Thermostat wasn’t opening all the way. Replaced thermostat, never happened again.

FjrVfr wrote: ↑Thu Mar 25, 2021 8:46 am I've got a Gen 2 (2012) with about 80K on the clock. In 4th or 5th gear at speed everything's fine. My temp gauge reads 4 or 5 bars out of 10. When I slow down in traffic or around town it moves up pretty quickly to 6 or 7 bars. Not catastrophic but it's going in the wrong direction and summer's coming. I'm going to try hydrogen peroxide on the fins along with compressed air from the back and as much water pressure as I can get from the garden hose. Coolant level is good and (reasonably) fresh. Fans come on around 6 bars and sound good. I only bring it up because it's been getting worse over the last 10K miles or so. It's also noticeably different from my previous (and basically identical) '06.

My question is, does the "good reading" at speed make it more or less likely to be the thermostat or water pump or radiator flow/blockage? I'm wondering what to try next.

Thanks as always.

Can't add a whole lot more, except to ensure rad is full. On my project bike I took the opportunity to clean the rad, and what you'll find (particularly if you do not have a fender extender) is the lower middle part will have tarry deposits and maybe some little stones. Careful when you clean it. Hydrogen peroxide for the bug guts, but for tar I soaked in naptha/mineral spirits, the appropriate solvents for that, rinsed with soap and water, carefully blew out with compressed air from the back side. Never did get it totally clean, I think mildly successful, as that shit is hardened in there. It was fine later.
Generally speaking, thermostats aren't a common failure item on an FJR, doesn't sound like it, coolant fans on a Gen2 should come on at 7 bars for sure and cool down/shut off at 5 bars. Normal running should be 4 bars on the road, 3 bars if ambient temp is rather cool. You didn't mention your ambient temp while seeing your issue....... but this time of year, Ohio isn't that hot... so it sounds like it's running a little too hot. Check that coolant level, let us know.

You're correct, mid 60s F. Sound advice. Will do and thanks.

Way back I had the same issue with my '06. Always ran 3-4 bars at speed regardless of outside temps. Over time it began to run 5 bars and on slowing down, heated up much quicker than usual. Cleaned radiator fins a couple times, flushed coolant, etc., seeing with little improvement. Changed thermostat...all was right and good in FJR world again!

~G

I thought I should provide an update. I took Bill & Escapefjrtist's advice and ordered a thermostat. I thought it's an easy and isolated fix and so I'd try that first. It took a week and a half to pass through the Suez canal but finally arrived. I boiled both new and old and didn't see much visual difference. The new seemed to open a bit faster but roughly the same amount. I should mention that coolant was full when I got in there as was the reservoir and looked like it had been poured yesterday.

On the road I thought I saw a difference but not a huge one so I took out the heavy chemicals. I had doubts about this helping because I regularly blast some water through the side gaps in the bodywork when washing to push junk out the front of the radiator. This time I removed the cowling and that wimpy grill on the front and went at it with hydrogen peroxide, Simple Green, a scrub brush and finally some Brākleen. It didn't look like that much came out but I rinsed/reassembled/rode to try it out. Fins looked surprisingly good even after using a medium brush. I think there was a mild improvement again. At very slow speeds it heats up to 7 or 8 bars but seems to cool back down more rapidly. It was 77 degrees (spring here in Ohio was last Monday afternoon between 2:00pm and 4:00) and so about 10 degrees warmer than the last outing. I suppose I'll just have to get used to it.

Sorry I didn't find a more definitive solution. Thanks for the advice.

-M

I chased something similar on my 2003. Mine got to the point where it was pissing fluid.

Checked and cleaned the rad cap
Replaced the rad cap
Replaced the thermostat
Removed and tried to clean the rad fins
Fresh coolant

End result I replaced the rad with a new one.

Problem solved.

Over the years the old rad offered limited air flow between the dirt and bent fins.

Good luck
Canadian FJR

Now that there's a new thermostat and rad cleaned, let's see what your new normal is..... I agree it sounds a little on the warm side, however.... at speeds about 30 mph, airflow through the rad should keep temps normal, so about 4 bars. Should stay that way at any speed faster than that. In town stuff, airflow is minimal, so it will likely climb to 5 bars. Stop and go will likely hit 7 bars eventually and the fans kick in. Fans/some airflow should bring it back to 5 bars and fans shut off. Move at faster speeds again, should drop to 4 bars and stay at 4 bars at highway speeds.
There really isn't anything else you can do to the system to improve it as is, I'd monitor for a while and see what normal average is... you'll have to judge if it's OK. No hard and fast rule but, say at 80F, steady 50mph it climbs above 4 bars, then the answer is likely a new rad if old one is blocked 10-20%/loose or bent fins.

Something put a big hole in my '04 radiator, near the top. A radiator shop fixed the radiator by injecting some kind of a high temperature goo into the cross tube which blocked off the entire tube and stopped the leak. With an entire cross tube blocked I had no abnormal coolant temperatures. FWIW.

Thank goodness the OP has a temperature gauge display with blocks and not actual coolant numbers; some of the early Gen III owners obsessed over the actual temperature fluctuations. I have the coolant temperature on one of my display pages but I don't normally watch it, if it's not overflowing coolant, it's fine

Just out of curiosity, does the OP's FJR have a fender extender or aftermarket lights (or some such thing) which may interfere with air flow?

Thanks all. Ray, I'd agree that I'm running a little warmer than normal. I don't see 4 bars (just below half) unless I'm 50mph for a decent stretch. Above about 40mph and I'm steady-state at 5 bars (halfway on a `12). Fans in stop and go bring me down to about 6. Alan, nothing aftermarket down there and again the fins look pretty darn good for their age/mileage. It might be mostly in my head but it seems warmer than the 100K I had on my '06 and about 80 on the '12.

Canadian FJR - how painful was the radiator swap for a shade-tree type? Do you remember what it cost you?

Thanks again,
Mark

Not that bad a job, there was some discussion on how-to either here or the other sandbox. I cant remember if I pulled the headers or left them on.
As far as cost, no idea. It was a few years back. I went stock, FJRob went aftermarket. I believe his is still working well.

viewtopic.php?f=60&t=3013&hilit=Radiator+replacement



Canadian FJR

Headers stay on..... kinda helps to have a helper to get the new one in place for the top mount bolts...

The only real issue I've had with removing radiators is the top two bolts. There is 'stuff' in the way of easily accessing these bolts. IIRC, some of the work with the top bolts was blind and done by feel.