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garcenw

Beating a dead horse - thermostats and 5th gen operating temperture

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I’m likely beating a dead horse here, but I can’t find a true consensus on older postings. On cool days, say 75 F (22 C) or less, what does your 5th gen VFR coolant temperature gauge settle at once you reach steady cruising on the highway or interstate? With the temperature sensor in the front head, one would expect something a little above thermostat opening temperature. The issue is that our VFRs have the bypass circuit in the thermostat housing that always allows some flow to the radiators irrespective of thermostat state. That flow path deosn't seem insignificant in diameter. It’s hard to know how much cooling that accomplishes without applying some engineering rigor. I figure the best way is to ask the members what they are seeing.

 
Probably the most useful responses would be those stating ambient temperature along with coolant temperature at that ambient temperature once you reach steady state while cruzing. Given the high failure rate of our thermostats, the highest confidence responses will be from those who recently replaced (say in the last few years?) their thermostats.
 
I haven’t replaced my thermostat since I’ve purchased the bike (this March) and being the third owner, I don’t know the history of what has occurred regarding thermostat replacement.  I suspect I’m in that grey area temperature-wise and suspect mine isn’t stuck, but doesn’t fully close (it reaches approximate thermostat temperature in ~3.5 miles of low traffic conditions on warm, say 80+ degree, days). Here are my steady state observations:
 
Steady speed = ~45 mph, ambient temperature = 88 degrees F -> temperature gauge = 181 degrees F
 
Steady Speed = 60 - 65 mph, ambient temperature = 73 degrees F -> temperature gauge = 165 degrees F
 
Thanks.
 
- Walt

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I'll have to generalize here due to the long history of my experience.

I've experienced the same temps as you state above. But at times, slow traffic in 80F to 100F plus, I've seen 230+ engine temps. Nothing above 235F. I've ridden across Death Valley with out experiencing the temp above 225F. I'd only worry if it approaches 250F. I believe the engine will shut down a little above 250F.  (I thought I read this somewhere, like the owners manual, but I cannot find the reference now.)

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Maxswell,

 

I normally see temps in the 200 - 210 F range in DC summer stop and go traffic. If I sit stationary for any great amount in time in DC summer traffic, my fan will come on at temperatures slightly above that and I ahven't seen anything as warm as 230 F. I think the highest I've ever seen was 226 F and that was idling in my driveway. I'm more concerned on the low end as mid 160's F seems a little low for steady state cruising at any temperature. I'm trying to determine what is normal for this bike before digging in to do a thermostat replacement.

 

Are your low end readings (i.e. 165 - 181 F) taken with a recently replaced thermostat?

 

- Walt

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My usual engine temperature for cold weather riding (<45 F) is 168 F.  If the outdoor temperature is above 60 F, I rarely see engine temps below 180 F.  This is with a brand new $30 price gouged OEM t-stat.

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My '99 runs around 175° if the outside air temp is 60° to 80°. Doesn't change much, maybe drop to 172° in

60° ambient temps. Rode Monday and the temperature was around 95° and coolant temps were running

around 180°. It's pretty consistent. Has about 43,000 miles.

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Front mount TL1000R rad, under 97*C in Sydney gridlocked/standstill traffic.

80* in free flowing traffic.

ambient temps maybe 18*-22*c because its winter.

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i have a 99, 60,000 miles replaced the thermostat at 45,000 just because i was under the throttle bodies at the time, and all described seem normal exactly what i experience all the disruptions above at speed and temp

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My 99 runs at or near 78C/172F nearly all of the time, unless I'm in slow traffic. If there is decent airflow, there is plenty of cooling available, and I don't do much/any city riding, nearly all my riding is on country roads, and no matter how hard I ride or how warm it gets (well, up to 30C/86F anyways) the temp stays below 80C/176F. 

 

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I replaced the thermostat soon after I got my bike (76000km) as the old one was jammed open. I'm a bit anal about maintenance and keep a close eye on thermostat function. A quick check is to start the bike from cold and keep a hand on the right hand radiator. It should stay stone cold until the bike gets to around 76-80C, then quickly get too hot to touch, that means the thermostat is closing fully when cold and opening at the appropriate temp. If it slowly heats from cold, then it is stuck open.

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Terry,

 

I thought about that as test, but the presence of the bypass circuit indicates at least some waste heat should be going to the radiators even with the thermostat closed. Perhaps the amount of waste heat being dumped is too small to notice until the thermostat opens.

 

- Walt

VFR800_5th_gen_cooling_flow_diagram.jpg

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9 hours ago, Terry said:

I replaced the thermostat soon after I got my bike (76000km) as the old one was jammed open. I'm a bit anal about maintenance and keep a close eye on thermostat function. A quick check is to start the bike from cold and keep a hand on the right hand radiator. It should stay stone cold until the bike gets to around 76-80C, then quickly get too hot to touch, that means the thermostat is closing fully when cold and opening at the appropriate temp. If it slowly heats from cold, then it is stuck open.

 

I second this, can confirm that this is the same as my 98 5th Gen. Right side rad cold until 175, then quickly itheats up, bike temp normalizes around 172. My old thermostat was frozen open also, and would begin to heat slowly from start. 

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20 hours ago, garcenw said:

Maxswell,

 

I normally see temps in the 200 - 210 F range in DC summer stop and go traffic. If I sit stationary for any great amount in time in DC summer traffic, my fan will come on at temperatures slightly above that and I ahven't seen anything as warm as 230 F. I think the highest I've ever seen was 226 F and that was idling in my driveway. I'm more concerned on the low end as mid 160's F seems a little low for steady state cruising at any temperature. I'm trying to determine what is normal for this bike before digging in to do a thermostat replacement.

 

Are your low end readings (i.e. 165 - 181 F) taken with a recently replaced thermostat?

 

- Walt

Walt, If it's cool out, I can state that I routinely see 168F - 178F. I can also say that, with four bikes with 36,000 miles to 105,000 miles (on my first, bought at 4,000 miles), I've never had a thermostat fail or replaced. Lucky me.

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Walt, your two steady speed coolant temp readings seem very good. I just finished a ride on my primary 2001 from SoCal to Seattle, Montana, Idaho, Wyoming, Colorado, Arizona, and back. Ambient temps were between 51F and 213F. After warming up, my coolant temp was always between 170-180F, except in stop and go traffic on mountain switchbacks where it went up to 222F, then the fan brought it back down to 210F, where it stabilized. In 213F ambient, the coolant temp stayed 209-212F while cruising steady at 75-80mph.

 

There's another 2001 in my life with only 9500 miles on its odometer that has me worried - this past mid June I picked it up with 8112 miles on the odometer in Austin TX, and in traffic around Austin [101F ambient, high humidity] coolant never went below 220F and was 225-229 most of the time. On the way back to CA, even at 75F ambient and 75mph, coolant was still 210-213F. In 111F ambient and a steady 80mph,  coolant temp was 225-233F. The coolant temp was always stable, it never jumped up or spiked. The previous owner purchased the motorcycle with 3500 miles on it and says it has always run on the hot side. The first factors to address are [1] the previous owner used a thermostat listed for a Mustang automobile from an auto parts store, and [2] the cooling fan has been flipped over in an attempt to draw cool air from outside the bodywork across the left radiator. My first actions will be to return the entire cooling system to OEM specs and have the radiators tested for flow/blockage. I'll post the process and results in a thread.

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My temperatures might seem OK, but what I haven't done is rigorous observations with ambient temperatures in the 50's , 40's, or 30's. It is rare here in DC in July/August, but I might see mid 50's in the evenings if I'm lucky and we get an unseasonably cool day. 40's will have to wait for the fall and 30's perhaps December. In these cooler temperatures, I suspect I will see cooler dash gauge temperatures. I don't want temperatures to get so low that condensation can settle or that parts don't reach there design intended sizes due to thermal expansion. The other piece of evidence I have is that I don't get the sudden warmup of the right radiator once the gauge temperature approaches nominal thermostat opening temperature. My right radiator starts warming up roughly instep with the dash gauge readout. I collected some data on that.

 

My procedure:

 

1)  Insert type T thermocouple in the center of right radiator. Thermocouple is touching it's nearest cooling channel. While this wont give you exactly the coolant temperature, it will be close, as the thermal resistance across the metal of the cooling channel is low and the channel to coolant thermal resistance is relatively low. In radiators, the big major thermal resistance is on the radiator-to-air side. In addition, I'm not so concerned with the exact coolant temperature. I'm more interested in the temporal thermal response of the radiator.

 

2) Thermocouple was connected to my multimeter which has a built in T-type thermocouple voltage to temperature converter.

 

3) Bike was at ambient temperature when started and I let it idle in my driveway. At periodic intervals, I noted elapsed time, dash gauge temperature, and radiator temperature. Note, at time = 0, my dash coolant temperature gauge obviously didn't give me a temperature (ambient was 80 - 81 F) as it doesn't read until the coolant hits 97 deg F. For that data point, I used the ambient temperature as the bike had been sitting for some time.

 

Below is a pic showing thermocouple placement. The data is shown in tabular form and is also plotted. As you can see, my radiator temperature increases roughly in step with the dash gauge. The radiator reads a little warmer than the dash gauge. That could be temperature sensor/thermocouple error, heat coming off the headers, or a combination of both.

 

 

 

T_couple_placement2.jpg

VFR_temp_data.jpg

VFR_temp_graph.jpg

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42 minutes ago, sfdownhill said:

Walt, your two steady speed coolant temp readings seem very good. I just finished a ride on my primary 2001 from SoCal to Seattle, Montana, Idaho, Wyoming, Colorado, Arizona, and back. Ambient temps were between 51F and 213F. After warming up, my coolant temp was always between 170-180F, except in stop and go traffic on mountain switchbacks where it went up to 222F, then the fan brought it back down to 210F, where it stabilized. In 213F ambient, the coolant temp stayed 209-212F while cruising steady at 75-80mph.

 

...

Uh, ambient temperatures of 213 F?

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1 hour ago, sfdownhill said:

Walt, your two steady speed coolant temp readings seem very good. I just finished a ride on my primary 2001 from SoCal to Seattle, Montana, Idaho, Wyoming, Colorado, Arizona, and back. Ambient temps were between 51F and 213F. After warming up, my coolant temp was always between 170-180F, except in stop and go traffic on mountain switchbacks where it went up to 222F, then the fan brought it back down to 210F, where it stabilized. In 213F ambient, the coolant temp stayed 209-212F while cruising steady at 75-80mph.

 

There's another 2001 in my life with only 9500 miles on its odometer that has me worried - this past mid June I picked it up with 8112 miles on the odometer in Austin TX, and in traffic around Austin [101F ambient, high humidity] coolant never went below 220F and was 225-229 most of the time. On the way back to CA, even at 75F ambient and 75mph, coolant was still 210-213F. In 111F ambient and a steady 80mph,  coolant temp was 225-233F. The coolant temp was always stable, it never jumped up or spiked. The previous owner purchased the motorcycle with 3500 miles on it and says it has always run on the hot side. The first factors to address are [1] the previous owner used a thermostat listed for a Mustang automobile from an auto parts store, and [2] the cooling fan has been flipped over in an attempt to draw cool air from outside the bodywork across the left radiator. My first actions will be to return the entire cooling system to OEM specs and have the radiators tested for flow/blockage. I'll post the process and results in a thread.

sfdownhill,

 

I don't know the spec for the Mustang, but car thermostats typically open in the 190 F to 205 F range. The thermostat is likely working fine, it's just the wrong thermostat. The thermostat is the killer because of all the hassle to get to it. You can change the thermostat and correct the fan first. BTW, turning the fan 180 degrees doesn't change the blade pitch direction and thus the flow direction is the same. All it does is reduce fan efficiency. The motor polarity musts be reversed to change flow direction. Those two changes will,  more than likely, fix your elevated temperatures. If not, then you can get the radiators flushed.

 

- Walt

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21 hours ago, FJ12Ryder said:

Uh, ambient temperatures of 213 F?

Ok, so it might not quite have been 213, but after 30 minutes it felt like it.

 

Walt - thanks 

20 hours ago, garcenw said:

sfdownhill,

 

I don't know the spec for the Mustang, but car thermostats typically open in the 190 F to 205 F range. The thermostat is likely working fine, it's just the wrong thermostat. The thermostat is the killer because of all the hassle to get to it. You can change the thermostat and correct the fan first. BTW, turning the fan 180 degrees doesn't change the blade pitch direction and thus the flow direction is the same. All it does is reduce fan efficiency. The motor polarity musts be reversed to change flow direction. Those two changes will,  more than likely, fix your elevated temperatures. If not, then you can get the radiators flushed.

 

- Walt

Wow Walt, you are exactly right about flipping the fan NOT reversing the flow. I’ve thought about how reversing the rotation would negate the aerodynamic advantage of the airfoil shape of the blades, but never did the 3D exercise of flipping the fan, so never discovered that the airflow would not reverse direction. I’m frickin laughing out loud at the power of suggestion...the P.O. said he flipped the fan to reverse airflow, and I didn’t question his premise.

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4 hours ago, sfdownhill said:

Ok, so it might not quite have been 213, but after 30 minutes it felt like it.

 

Walt - thanks 

Wow Walt, you are exactly right about flipping the fan NOT reversing the flow. I’ve thought about how reversing the rotation would negate the aerodynamic advantage of the airfoil shape of the blades, but never did the 3D exercise of flipping the fan, so never discovered that the airflow would not reverse direction. I’m frickin laughing out loud at the power of suggestion...the P.O. said he flipped the fan to reverse airflow, and I didn’t question his premise.

 

I had to go out to the garage and find a spare fan to actually physically flip it over...🙄

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Ok, I'm a wee bit confused, so excuse the question if I'm off here. I just read how the RC51is plumped up and rc51 seems to have the same heating issues.  but one guy seems to have found a sorta cure,  but I'm not sure if it's possible on the 5th gen. So I ask , From what I understand is the RC51 system has the radiators where they run parallel are the VFR thata way too? he re routed the plumpig so they worked in series.  He claims it keep temps from getting out of hand and things cooled off faster.   https://www.fireblades.org/forums/honda-rc51/104793-rc51-overheating-problem-solved.html

 

That said in my running around today I found at 89 degrees outside on the freeway it maintain 182.  in stop and go traffic at the same temp outside it was 210-212ish, at one light the fan came on at 219 but once moving above 35 it cooled back down to 186 then less once back on the freeway. Which for the most part is what it's always done.  does bug me a bit that there is quite a cooling  hic up even though it seems to sorta work.  

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RVFR,

 

Folks get worked up over the temps over 200 F, but I don't see those as an issue, unless the temps get past the warning temp level on the gauge. Most cars run around 195 to 210 with nominal loads. I wouldn't worry much about temps in the 200 - 235 F range.

 

My concern is on the low end of the temperature scale once warmed up. Are steady state temps below thermostat temps normal? Normally not, but unlike some other vehicles, the VFR800 bypass goes to the radiator. That bypass is not insignificant in size, so there is the potential the some heat dissipation always occurs at the radiators even when the thermostat is closed. I'm trying to establish what are the normal steady state temperatures are on cool days before I decide to pull my thermostat out and test it. The temperatures I'm seeing (a little below thermostat opening temperature) are in the gray area if one assumes the bypass allows some cooling to occur and also accounts for the acceptable error in the head temperature sensor (which is a thermistor).

 

- Walt

 

 

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6 hours ago, RVFR said:

That said in my running around today I found at 89 degrees outside on the freeway it maintain 182.  in stop and go traffic at the same temp outside it was 210-212ish, at one light the fan came on at 219 but once moving above 35 it cooled back down to 186 then less once back on the freeway. Which for the most part is what it's always done.  does bug me a bit that there is quite a cooling  hic up even though it seems to sorta work.  

 

Your cooling system works. Select air temp on your display and call it a day. 

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On 7/12/2018 at 3:44 PM, garcenw said:

Steady Speed = 60 - 65 mph, ambient temperature = 73 degrees F -> temperature gauge = 165 degrees F

 

That does seem a bit low, but you don't mention how long it had been running and if it had been over that temp earlier in the same ride. If it was the first miles of your ride that day, it could just have not gotten the chance to warm past that point? If you had seen 180s in stop and go, and then gotten into clean air running in 6th gear for an extended period, that might be too cool. I've found a 100 degree differential between ambient and water is generally the case in average temps.

If you aren't having running issues, I would save it for a "big maintenance project." I just replaced my working thermostat because I was replacing all the hoses with silicone, and the water pump because it was leaking. Since I was in there I pulled the injectors and sent them out for cleaning, and replaced the fuel filter.

The only time I replaced the t'stat on it's own was to solve an odd behavior. It would constantly cycle up and down between approximately 170 and 185 in steady speeds in clean air. I ignored it for a long time with no problems, but finally decided to change it to see if it cleared up. It did. This last change was purely for the sake of doing it while it was accessible, literally in my hands already. 

 

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