Bike running one bar lower on temp gauge

[TownsendsFJR1300]

The slight change in temp may be normal, BUT he is having a new stumble that WASN'T there before.

Something is amiss, if it was a Gen 1 bike, it could be the connector under the fuel tank corroding, causing the stumbling issue (which I found the problem with the help of this forum).

I know my 04 doesn't have any stumble, can/will anyone address that?

 

[SoCalFJR1300]

But calling me (and several of the other more experienced FJR folks on the forum) irresponsible for suggesting he "not worry about it" is an attitude that I just don't have much of a need for.

I apologize Fred......you're right the "irresponsible" quote was not needed, didn't see that, my bad.

 

[LAF]

The slight change in temp may be normal, BUT he is having a new stumble that WASN'T there before.
Something is amiss, if it was a Gen 1 bike, it could be the connector under the fuel tank corroding, causing the stumbling issue (which I found the problem with the help of this forum).

I know my 04 doesn't have any stumble, can/will anyone address that?

Well who is to say the two are related? Just because two things are happening does not mean they are because one or the other. The stumble may just be a TB sync issue, a wet plug, a loose plug wire, or a pulled wire from the plug cap, split cap on the vacuum ports, or any number of things. One bar lower could be any number of things also but my bet is on a gauge that may be wonkers, or maybe even the beginning of a dreaded Spider Bite.

I do not fault the OP for wanting to look into it and try to resolve it but his approach and his resistance that all advice is wrong is not the way to approach guys on this Forum who know and take the time to reply and help. These guys are here on goodwill and to help. Yes they may be wrong but there is a way to teach a old dog new tricks and insulting and calling bullshit is not one of them. Say thank you, and proof it out, and then come back and tell/show how or what you did. Everyone likes to learn and see new things, but no one likes slapped in the chops for trying to help. You will play hell getting help the next time when it may be more significant and you will be outside looking in.

 

[jpcfjr]

As predicted, this non-problem has continued to get worse. The bike is now running 3 to 4 bars lower than it used to. I actually saw three bars this morning.

New evidence suggests a thermostat issue. Since the temperature gauge is indicating an even lower level but there has no corresponding additional drop in engine performance beyond what I've already seen, the temperature sensor cannot be the culprit. While I thought the test of the temp sensor might indicate an issue because it was on the edge of the performance envelop, with a temp reading this low on the dash the engine performance would certainly have dropped off if it was a false reading. Conclusion: the engine is really running much cooler. While this is not a problem now with ambient temps in the 90's, when it's below freezing I'd be having issues. Since I ride year round in all temps (I've seen 6 degrees on the dash) I need to fix this.

As I originally suggested, I discounted the thermostat because I've personally never seen one stick open. And I've replaced a lot of bad thermostats in my years of working on engines. However, there appears to be no other explanation. I have ordered a new thermostat. In the mean time I've replaced the temperature sensor (which did test much better...in the middle of the acceptable range for resistance at the specified temp) and the radiator cap as an additional cheap insurance policy. I'm $65 in so far and about an hour of work so no biggie.

I fully expect to pull out a stuck open thermostat. If not I'll be completely baffled. Stay tuned.

 

[ionbeam]

Most modern thermostats are designed as "Fail Safe" and fail open, unlike the dark ages where they would fail closed and overheat the system. The only ways your bike can be running this cold is a stuck open thermostat or a faulty reading on the display. The thermostat is made to be fully open at 185º F, what do you read when you hold a cooking thermometer on the top of the radiator? With your ambient over 90º your thermostat should be fully open anyway and you should be reading normal temperature on the display. If your thermostat is stuck open your temp display should indicate an abnormally long warm up period.

One bar low is an indicator, but not a problem, your FJR will still run fine. Now running 3-4 bars low shows something isn't right, but it is not an issue to drive your FJR until the (now) problem is fixed.

 

[jpcfjr]

Huh, I've never heard of a thermostat that was capable of failing open let alone one specifically designed to do that. Even the one in the wife's Acura (2005 TL) failed to open properly and I noticed the higher gauge reading and replaced it...solved the problem.

I discussed the heat up time at length with the mechanic at the dealership and he suggested the same thing. However, I'm not really seeing a longer heat up time which again threw me off the scent. It might be longer but I honestly don't remember. He also originally suggested a possible faulty display but I don't think that is the case. I can get the heat up to 7 bars by idling the bike for a while. It used to be able to get up to 8 bars but I can't get there now. The wild swing in temp reading is what you would see if the thermostat were removed completely so the stuck open theory is probably correct.

One other thought. It may not be open all the time. It may be starting out closed during warm up but then sticking open when it's hot. That would make sense too.

 

[ajpagosa]

Huh, I've never heard of a thermostat that was capable of failing open let alone one specifically designed to do that. Even the one in the wife's Acura (2005 TL) failed to open properly and I noticed the higher gauge reading and replaced it...solved the problem.
I discussed the heat up time at length with the mechanic at the dealership and he suggested the same thing. However, I'm not really seeing a longer heat up time which again threw me off the scent. It might be longer but I honestly don't remember. He also originally suggested a possible faulty display but I don't think that is the case. I can get the heat up to 7 bars by idling the bike for a while. It used to be able to get up to 8 bars but I can't get there now. The wild swing in temp reading is what you would see if the thermostat were removed completely so the stuck open theory is probably correct.

One other thought. It may not be open all the time. It may be starting out closed during warm up but then sticking open when it's hot. That would make sense too.

Nah, they tend to fail open. Dead giveaway is if it warms up idling or in slow traffic, then quickly drops too low at higher speeds. Just replaced one on my older car and that behavior is what indicated to me it had failed (open). Replaced it and everything's fine.

 

[Donal]

I'm getting slightly lost here........... Your bike is a 2009, 'normal' reading is 4 bars for a Gen2, yet you say "it's running 3-4 bars lower than it used to". The only time it will get up to 7-8 bars is with the bike stationary or moving very slowly. At this point the fans will kick in. I find I need to be going at ~50 MPH or faster for optimum cooling.

 

[jpcfjr]

Normal reading for my bike is 7 or 8 bars when stopped at a light in traffic with the fan kicking on at 8 and dropping it down to 7. Running in the summer at speed 6 to 7 bars is normal. Now I'm getting no more than 4. When it's very cold out I can see 4 bars but that is below freezing and moving.

 

[jpcfjr]

The Thermostat appears to be the culprit. I pulled out the old one last night and while not stuck open it has a significant scraped portion on the brass inner cylinder that moves inside the spring. This shaft has been scraping against the outer bracket of the thermostat for some time.

There is no indication that this thermostat has any sort of mechanism to fail in the open position. And as I’ve mentioned, I’ve never seen or heard of such a thing. The dozen or so thermostats I’ve replaced in the last 35 years have all failed closed or failed to open fully. This one it seems failed in such a way as to scrape against the bracket when heated up and open thus closing very slowly. Just luck of the draw I guess.

Funny that I posited this scenario in my first post…then discounted it because I’d never seen this happen before. Should always go with your first answer on the test?

Based on what I saw on the dash this morning I suspect that the original thermostat was bad from day one. The temp reading on the dash went up to 4 bars and stayed there, rock steady, until I sat at a light for a while. As previously mentioned, the bike used to sit at 6 to 7 bars and hit 8 at long stops. I’m thinking it should have been at 4 all along (as the guy from England mentioned). It felt as if the bike was running smoother now too…too early to tell if that is just euphoria from fixing this issue.

Finally, please don’t ignore a change in your bike no matter what people may suggest. A change is an indicator that something is potentially wrong. If I had ignored this change, eventually the thermostat would have stuck closed and probably not at an opportune moment. And bonus, since my bike is still under warranty, I should be able to get the $42 back once I bring in the defective part.

 

[ionbeam]

Ahem:

 

[zed88]

While we are on topic what's the proper way to bleed a gen 2 radiator? I think mine might have air

 

[jpcfjr]

Tru Dat!

 

[jpcfjr]

While we are on topic what's the proper way to bleed a gen 2 radiator? I think mine might have air

The way I do it is run the engine with the radiator cap off and keep putting coolant in until the engine is heated up and no more coolant can be added. Seems to work for me.

 

[jcyuhn]

While we are on topic what's the proper way to bleed a gen 2 radiator? I think mine might have air

The way I do it is run the engine with the radiator cap off and keep putting coolant in until the engine is heated up and no more coolant can be added. Seems to work for me.

I use that method and still end up with some air pockets. Last time I changed the coolant, the temp guage acted wonky on the first ride; it was bouncing between 4 -5 bars while riding on a cool day. The fix is a couple of heat cycles and a quick blast or two up toward redline. Be sure to top up the overflow tank, as the engine will draw in additional coolant as the air pockets are worked out.

 

[jpcfjr]

Yeah, never get all the air out that way but you get enough for the system to take care of the remaining air. If there is too much air in the system it cannot produce the necessary negative pressure to allow fluid in from the overflow..don't ask me how I know this.

 

[Fred W]

The Thermostat appears to be the culprit. I pulled out the old one last night and while not stuck open it has a significant scraped portion on the brass inner cylinder that moves inside the spring. This shaft has been scraping against the outer bracket of the thermostat for some time.
There is no indication that this thermostat has any sort of mechanism to fail in the open position. And as I’ve mentioned, I’ve never seen or heard of such a thing. The dozen or so thermostats I’ve replaced in the last 35 years have all failed closed or failed to open fully. This one it seems failed in such a way as to scrape against the bracket when heated up and open thus closing very slowly. Just luck of the draw I guess.

Funny that I posited this scenario in my first post…then discounted it because I’d never seen this happen before. Should always go with your first answer on the test?

Based on what I saw on the dash this morning I suspect that the original thermostat was bad from day one. The temp reading on the dash went up to 4 bars and stayed there, rock steady, until I sat at a light for a while. As previously mentioned, the bike used to sit at 6 to 7 bars and hit 8 at long stops. I’m thinking it should have been at 4 all along (as the guy from England mentioned). It felt as if the bike was running smoother now too…too early to tell if that is just euphoria from fixing this issue.

Finally, please don’t ignore a change in your bike no matter what people may suggest. A change is an indicator that something is potentially wrong. If I had ignored this change, eventually the thermostat would have stuck closed and probably not at an opportune moment. And bonus, since my bike is still under warranty, I should be able to get the $42 back once I bring in the defective part.

So, what was the cause of the driveability issues that you claimed began coincidentally with the start of the more normal temp readings?

 

[wfooshee]

Good luck with getting a refund on that part. You may find that if they don't do the work, it ain't warranty service.

I don't mean "good luck with that" sarcastically. I just wonder if you have any hope of it.

 

[08FJR4ME]

In the last few days my '09 FJR has been at 5 bars on the temp gauge and topping out at 7 bars when idling at red lights. This is one bar lower than normal especially for mid 90's temps. I'm thinking the thermostat is shot but thought I'd ask here before I started replacing things. I've also experienced some stumbling and roughness at higher revs...I'm thinking the computer is thinking the bike isn't heated up and is enriching the mixture.
Anyway, anyone have thoughts or experience with this problem? The bike has 56,350 miles.

Thanks.

A ) You stated you have a problem.

B ) In the same paragraph you gave your own solutions and ideas to your problem.

C ) You open yourself up at the end for suggestions. (ANY THOUGHTS)

You then go on to diagnose your situation still without listening to what some folks say to try and help you. You may have guessed right in the end but you lost a lot of respect in the interum. There are better ways to discuss things here and be more open minded. You won't always get the answers you would like to hear. When you open yourself up to ANY THOUGHTS you need to respect those comments also even if you don't agree.

Nuff said,

Dave

 

[ajpagosa]

OP, I assume you can use Google? Try searching on "thermostat stuck open", it is very common. Please stop insisting it isn't. It is not so much they are designed to fail wide open, they just often fail in a way that does not close & seal completely. For a lot of reasons. Metal fails, spring fails, bad seal, internal wax doesn't soften/harden correctly anymore. Or something as simple a blockage preventing a good seal. You name it, it happens.