Extreme Fluctuation in Digital Coolant Read-out on 2016ES... Others Afflicted?

Have had my 2016ES for seven months with 8K miles at present. Have recently noticed totally random digital readings when I first begin riding after warm-up. Digital display will randomly show 158... then two seconds later show 175... then go directly to 149... then 173... ??? Meanwhile, the bike performs normally, and the coolant level is where it should be.

At first I thought maybe it needed time to get to full riding temperature before the display was in sync with the coolant temp. Or maybe it's because the outside temps have fallen now that winter is approaching... Quickly ruled out the second possibility because it doesn't get cold in Phoenix...

Yesterday's experience... out for a breakfast ride with several buddies... the temperature gauge bounced around from a low of 149 to a high of 188 the entire time we road to our breakfast spot. It wasn't like the bike was idling at a stop light and the temps were fluctuating... I was at 5th and 6th gear speeds most of the time... This went on for an hour and twenty minutes until we stopped for breakfast.

The rub... started the bike up when we finished breakfast and the digital display worked flawlessly the remainder of the ride.........

This phenomenon has only occurred the last few weeks... no issues before that.

Does the FJR have a temperature sending unit that could be faulty?

Appreciate any comments...

I don't have a 16, so this is apples to oranges. While (we think) I was chasing air in the cooling system (long story), I would, in addition to occasional mild overheat at long stops, see abnormal fluctuation in temps on the display, while underway. Not broad enough to cause concern, but it was a marked change in behavior, or in data displayed, at least. Probably unrelated to your observation. Good luck with the diagnosis.

OMG! Your bike is about to EXPLODE into flames! Just kidding.

Read this. Ambient air temperature, air flow through the radiator, cooling fan operation, right wrist twitching, stop-and-go conditions; all will affect coolant temp, and with the small amount of coolant in our bikes, the spikes in temp are not unusual.

Does winter in AZ mean ambient air is lower than 180F? That could mean adequate cooling from ambient air before the fan turns on.

Two suggestions:

1) Continue to monitor the coolant temp carefully. Coolant is pressurized and can exceed 212F without issues.

2) Stop monitoring the coolant temp. Ride more, worry less.

I have chosen procedure #2, and changed my menu so that coolant temp is not on the normally displayed screen.

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PS: Advanced Search (gear icon to the right of the search box). Search for "coolant temp" and use the quotation marks. I got 106 hits, which includes the one linked above.

This is what happens when we go from a simple, reliable bar system, where so long as the bars are in range all is good, to a number readout system that gives people more crap to needlessly worry about.

It's been going on since 2013, when Yamaha made the coolant temp an actual number. Unless you're overheating or smelling coolant, you're fine.

^^^ this exactly. Honda made the same mistake way back in 1998 when they put a digital display of coolant temp on the VFR800. All the new riders would freak out when they saw the temperature moving around and climbing up above the 212F boiling point.

The fix then is the same fix for the FJR now. Don't worry about it unless/until it starts puking coolant on the ground.

An interesting automotive corollary is that most car manufacturers had idiot lights in the dashes and everything was fine. Then they started putting "fancy" gauge packages in the more expensive models that included battery voltage, oil pressure and, yes, coolant temperature. The early gauges were fairly accurate and you could read the results of what was being monitored, but this caused a lot of unnecessary angst and complaints from customers when they saw the fluctuations.

This caused many of the manufacturers to redesign the scales of the gauges and remove any meaningful numbers, replaced by a wide band in the middle saying "normal". Some manufacturers went so far as to redesign the instruments guts to always point to the exact center of "normal" unless there was a fault. The analog gauges had reverted to analog idiot lights. What goes around comes around.

Easy fix...just change the display to another screen, and ride the bike.

I've also read that the analog gauges in most cars are damped (is that the right word?) so that they don't fluctuate quickly. Instead of jumping around to keep up with the temps accurately they sort of slowly ooze from one reading to the next so people don't get so excited.

Appreciate the comments (the picture too)...

Guess I thought it strange that I had no problem with summer heat in Phoenix (30+ days of 110+ heat this year)... only noticed this since early morning temps have been in the 40s and 50s.

Will take everyone's advice... "Change the screen and Enjoy the Ride"...

And now that the CEL concern has an ECU fix from the mothership, all is well...

I always enjoyed when the good professor Ionbeam would chime in on these sort of posts.

AZcruising said:

Appreciate the comments (the picture too)...
Guess I thought it strange that I had no problem with summer heat in Phoenix (30+ days of 110+ heat this year)... only noticed this since early morning temps have been in the 40s and 50s.

Will take everyone's advice... "Change the screen and Enjoy the Ride"...

And now that the CEL concern has an ECU fix from the mothership, all is well...

Click to expand...

It seems logical, to me anyway, that the lower the ambient temperature is, the more quickly the coolant in the radiator would cool and the more quickly the temperature would change as the thermostat opens and closes.

Pays to search the forum instead of asking the same questions that's been asked a hundred times before.

Gets a bit "ho hum" after awhile

Pays to read this https://www.fjrforum.com/forum//index.php/forum/59-new-forum-members/

I observed some unusual fluctuations on a ride yesterday. 55 degrees out, a mix of 5th and 6th gears, speeds averaging 60 to 65 mph. Coolant temperature rose repeatedly from 149 to 177, then back to 149, in cycles of maybe 15 to 20 seconds. I call that unusual because my Super Ténéré never did that. Has to be the thermostat opening and closing, I'm guessing. Hope it's not detrimental to engine longevity.

Normal. Engine will last far longer than you will.

Imagine how a burst of 55F water feels to your 250F engine as the thermostat opens up a winter-weather radiator. Coolant temperature will drop rapidly towards that of a freshly-made martini. Thermostat closes, allowing those high-revving inline four cylinders to heat back up to 250F just as quickly.

Advanced Search (gear icon to the right of the search box). Search for "coolant temp" and use the quotation marks. I got 106 hits, which includes this one.

Some apply to Gen3, but I'll bet many Gen2 posts apply also, since I can't imagine Momma Yama redesigned the cooling system.

(1) it ain't broke, so no need to fix it, and

(2) it would have been mentioned in the 2016 press releases.

In consideration of the current wintery weather in the northeast, lets take a few minutes to take a look at the cooling system of the FJR and see if we can come up with a plausible reason for this often noted temperature fluctuation phenomenon:

The primary coolant path from the engine exits via the metal coolant pipe at the top of the head, the one you have to remove to check the valves, callout #1 below. At the right end of that pipe is where the coolant temp sensor lives. The left end of that pipe is where the coolant exits via hose #2/6/9, which runs down around the frame and loops back up to the thermostat housing and fill port assembly (#10).

From there it runs down to the top of the radiator (4) via hose # 8. The secondary coolant path to the radiator via hose 3 is coming from the oil cooler mounted on the front of the engine.



After passing downward through the radiator core and being significantly cooled down, the coolant goes to the suction side of the water pump via hose #16. The pressure side of the pump is returned to the engine at the front of the cylinder block hose 14/17, and also branches off to the oil cooler on the front of the engine via hose 13.



We can see that the thermostat housing is down-stream of the coolant sensor by a significant amount (hoses 2/6/9). Therefore the sensor will see the temperature of coolant exiting from the engine significantly before the thermostat will feel it and open or close further.

Assuming the radiator has good air flow the coolant exiting the radiator will be approaching ambient air temperature. While in the summer that could be 90 - 100 degrees F, in cooler weather it may be 50 or 60 degrees lower.

The thermostat doesn't open until it senses the coolant slowly trickling past the closed stat (through the bypass hole) at 180 or 190 degrees F, and when it does open, the engine will be ingesting cold coolant until it passes all the way through the engine, past the temp sensor, and back to the thermostat.

The temperature fluctuations we see on the display are due to the delay of the thermostat, thermal hysteresis of the cooling system. Completely normal, and nothing at all to worry about.

The only difference in the cooling system from Gen 2 to Gen 3 was the deletion of the coolant path to the throttle body fast idle, wax motor actuator. On 1st and 2nd Gens it used the coolant temp coming out of the engine to actuate a wax motor that would open 4 little air bypass pistons in the 4 throttle bodies to bump up the idle speed when stone cold.

On 1st Gens the thermostat was located just above the metal coolant manifold on top of the valve cover. The hose distance was significantly shorter than 2nd Gens and later. 1st Gens also had a courser temperature display than 2nd Gens. Of course the biggest difference with the 3rd Gens is they tell you what the temperature of the coolant exiting the engine digitally and that display is not buffered, hence the fluctuating numbers and angst.

Thanks, Fred, for the comprehensive information!

My 2014 is the same. Was concerned at first, then determined it had to be the location of the sensor. Runs perfect.

One of my all-time favorite radio shows was Click and Clack I was listening one day when someone called in to say he'd installed a temp gauge on his truck and was concerned at how much the temperatures fluctuated. They explained to him that factory gauges are damped so they don't fluctuate very quickly because it upsets people.

I've enjoyed reading this thread and noticed all that was discussed happens to my bike too. Good to know it's all normal.

I want to report that riding across Arizona with an ambient temp of 106 the bike temp held at 193 for several hours. It ran perfectly.

its just rain posted: ..... It ran perfectly.

Click to expand...

Succinct characterization of an FJR.

Now, about your screen name .... I spent two of the past four weekends riding 500 miles round trip to see my mother in SC. It's pretty hot down south in July, and I rode with absolutely no regard for raingear: ventilated jacket and pants, didn't even pack the rain liners.

"It's just rain," I said, when I spotted bikers cowering under a bridge struggling to put on their sauna-like rainsuits.

"It's just rain," I said, when my brother telephoned me about upcoming showers as we crossed paths; him heading west to ATL and me heading east to SC.

"It's just rain," I said, when Mom asked if I was prepared for the ever-present summertime threat of scattered thundershowers.

Am I alone with this attitude? (Except, of course, for the fine Forum member I quoted.)