davesweet63 Posted April 8, 2017 Share Posted April 8, 2017 Hi all! I just bought a 98 VFR, I wanted to make sure the cooling fan worked so ran the bike, got to 110C and nothing so shut it down, I have the owners manual It says that 122C Is considered as overheating So went out and tried again, 116C the fan kicks in and drops back to about 105C. My Question! Is this Normal? What sort of temp will they run at whilst on the move with an ambient temp of around 20/25C.. All other Bikes and Cars I've owned the fan comes in at around 100C. Thanks in advance for your help. Link to comment Share on other sites More sharing options...
GreginDenver Posted April 8, 2017 Share Posted April 8, 2017 VFR thermostats are known to randomly stick. That is to say: when these thermostats fail the failure can occur with the thermostat full open or full closed or anywhere in between. If your VFR has never had its thermostat replaced it's definitely time for that to be done. If your thermostat has failed in the stuck-closed position the bike could easily overheat. The coolant temperature sensor is mounted in the engine block while the fan switch is mounted in one of the radiators. So if the thermostat is stuck full closed the hot coolant won't be circulating through the radiators fast enough to heat up and trigger the fan switch before the engine overheats. Your '98 is now 19 years old, man up and do the thermostat replacement. Link to comment Share on other sites More sharing options...
hellindustries Posted April 8, 2017 Share Posted April 8, 2017 Yup. Sounds like you need a new 'stat. My 2000 tends to come on around 95-100c and i've never seen it go higher than 109c Link to comment Share on other sites More sharing options...
Member Contributer Terry Posted April 9, 2017 Member Contributer Share Posted April 9, 2017 Welcome aboard Dave. We're talking about a few different systems here. The fan switch is independent of the thermostat and temperature gauge, it is just a switch that should close around 100C and open again below 95C. Your fan switch sounds like is operating correctly but at a higher than normal temperature. That might be a faulty switch or the temperature readout might be a bit high. The thermostat is a purely mechanical device that opens or closes at around 80C to regulate the flow of coolant through the radiators to maintain the engine temp. If it is working properly, when you are moving steadily you should see 78-82C. If it jams open the bike may run at a lower temp, and will be slow to warm up. If it jams shut then you will overheat the engine quickly. In my experience they will more likely jam open. You can do a simple test by starting the bike from cold and keeping a hand on a radiator. If it stays cold until the engine gets to 78-80C then suddenly gets too hot to touch, all is well. If it slowly heats up from the time the engine starts, it is jammed open. If the radiator stays cold after 82C then it is probably jammed shut. Lastly the engine coolant temp sensor is a resistance device on the back of the front head that increases in resistance with temperature. If you have some dirty connectors increasing the resistance then it will read high. There are diagnostic tests for resistance at set temps, I'd be inclined to use an IR thermometer to double check the readings. Link to comment Share on other sites More sharing options...
GreginDenver Posted April 9, 2017 Share Posted April 9, 2017 11 hours ago, Terry said: Welcome aboard Dave. We're talking about a few different systems here. The fan switch is independent of the thermostat and temperature gauge, it is just a switch that should close around 100C and open again below 95C. Your fan switch sounds like is operating correctly but at a higher than normal temperature. That might be a faulty switch or the temperature readout might be a bit high. The thermostat is a purely mechanical device that opens or closes at around 80C to regulate the flow of coolant through the radiators to maintain the engine temp. If it is working properly, when you are moving steadily you should see 78-82C. If it jams open the bike may run at a lower temp, and will be slow to warm up. If it jams shut then you will overheat the engine quickly. In my experience they will more likely jam open. You can do a simple test by starting the bike from cold and keeping a hand on a radiator. If it stays cold until the engine gets to 78-80C then suddenly gets too hot to touch, all is well. If it slowly heats up from the time the engine starts, it is jammed open. If the radiator stays cold after 82C then it is probably jammed shut. Lastly the engine coolant temp sensor is a resistance device on the back of the front head that increases in resistance with temperature. If you have some dirty connectors increasing the resistance then it will read high. There are diagnostic tests for resistance at set temps, I'd be inclined to use an IR thermometer to double check the readings. Everything you wrote here is correct except for the item I underlined-bolded. Page 19-15 of the Honda VFR800 Service Manual shows that when tested (as directed on that page of the Service Manual) the Engine Coolant Temperature Sensor actually decreases in resistance as temperature rises. Link to comment Share on other sites More sharing options...
Member Contributer RolandHTG Posted April 9, 2017 Member Contributer Share Posted April 9, 2017 A point that has not been mentioned is the poor efficiency of the sideways facing radiators. In slow traffic the VFR is going to run hotter than most water cooled bikes. I found it necessary to install a manual radiator switch and would use it whenever speed dropped to below 40 to 50 mph, due to traffic, in hot weather. And this was AFTER I replaced my thermostat. Link to comment Share on other sites More sharing options...
GreginDenver Posted April 9, 2017 Share Posted April 9, 2017 1 hour ago, RolandHTG said: A point that has not been mentioned is the poor efficiency of the sideways facing radiators. In slow traffic the VFR is going to run hotter than most water cooled bikes. I found it necessary to install a manual radiator switch and would use it whenever speed dropped to below 40 to 50 mph, due to traffic, in hot weather. And this was AFTER I replaced my thermostat. No offense intended here, but you're propagating the myth that the 5th-Gen VFR800 "runs hot", suggesting that the bike was under-engineered by Honda or that the Honda designers somehow made a mistake in the design (as if this well educated and highly trained group of Honda vehicle engineers and designers was somehow incapable of doing the necessary math to figure out how much radiator surface area was required to provide the correct amount of heat rejection, and that subsequent pre-production testing of the design also failed to reveal this flaw). The truth is that a 5th-Gen VFR800 does not run hot when it has good coolant in the system, when the water pump in good condition, when the thermostat is operating properly (not stuck in one position), and (this is the part that is almost always overlooked) when the radiators aren't covered in years and years of road grime and goo and when the cooling vanes of the radiators aren't clogged up with many, many tiny rocks and other bits of road debris. Occasionally taking the time to clean the accumulated layer of road grime and goo off the outside of the radiators and to remove all the little rocks and bits of debris that get stuck in between the vanes of the radiators is really just part of the ongoing maintenance the bike should get, just the same as occasionally changing the coolant itself. But people rarely do this, and as time goes by and the road grime and goo and little rocks reduce the radiator's ability to flow air and transfer heat away to the atmosphere. Now, I can understand how somebody who's riding around on a 5th-Gen VFR800 with (to pull a completely random number out of the air) 145,000 miles on it might decide that his bike "runs hot", because it does run hot. But thats only because this same person has never taken the time to clean the built-up layer of grime and goo off the bike's radiators, nor has this hypothetical high-milage 5th-Gen VFR800 owner ever bothered to remove all the little rocks and other bits of road debris that combine to obstruct proper airflow. Link to comment Share on other sites More sharing options...
Member Contributer KevCarver Posted April 9, 2017 Member Contributer Share Posted April 9, 2017 I basically agree with GreginDenver but I would further add that the bike does indeed operate within the design parameters set forth by Honda. At least mine does in general usage; 1999 model year bought with 20,500 miles and currently over 102,600 miles. The bike spent the first half of it's life in Florida, then on to GA and finally TN. I also owned a side rad RC51 for a few years. Both bikes run at higher temps than comparable front radiator bikes, but that's not a fair comparison. I've had to replace the water pump (was doing some track days and swapping coolant between cheap parts store brand and plain distilled water) and the t'stat at separate times, but basically run it with the temp display set to ambient air temp. I have long felt this is the single greatest "fix" for VFR owners complaining about "running hot." As long as the bike has good coolant (I run it with Honda Type 2 bought at the car dealer for about $20), and properly functioning t'stat, pump, and fan, you should "set it and forget it" to ambient air temp. Now a ToroCharger 6th Gen in TN summer is a whole other situation! Link to comment Share on other sites More sharing options...
Member Contributer RolandHTG Posted April 9, 2017 Member Contributer Share Posted April 9, 2017 I do not doubt the competency of the Honda engineers but I do believe they make compromises. The 5th gen was based on a V-4 design that was intended to be competitive in Superbike racing. I don't think that parameter quite fits the broader needs of a sport tourer. True I had 145,000 on my 99 but the cooling problems showed up 90,000 miles earlier. Running hard in the Smokie Mountains and then getting stuck in tourist town traffic was too much for the side mounted radiators. I just think they did not get enough air flow. I can vividly recall my frustration watching the temp readout climb as the speed of the traffic I was behind dropped. Link to comment Share on other sites More sharing options...
davesweet63 Posted April 10, 2017 Author Share Posted April 10, 2017 Thanks for the replies. The thermostat is working fine, I will get new temp sensor and fan switch. Link to comment Share on other sites More sharing options...
GreginDenver Posted April 10, 2017 Share Posted April 10, 2017 4 hours ago, davesweet63 said: Thanks for the replies. The thermostat is working fine, I will get new temp sensor and fan switch. Good to hear that the thermostat is fine, however, history and the experience of a good number of other owners would strongly indicate that if you own a 5th-Gen VFR and it still has its original thermostat you're running on borrowed time. Obviously, there will be a bell-curve of failure and it could be that you've got the really long-lasting outlier that defines the good tail-end of that bell-curve. Link to comment Share on other sites More sharing options...
Member Contributer MaxSwell Posted April 13, 2017 Member Contributer Share Posted April 13, 2017 Having owned five fifth gens and kept a close eye on engine temperatures (in F), early on I was alarmed at how "hot" the machine ran. My radiator fan came on ~217F (103C) and went as high (a couple of times) as 235F (112.7C). Hot days in slow traffic were the hottest. But I now realize that is all normal for these machines. My first fifth went 105,000mi (169,000km) and, having had it's last oil change sent to Blackstone Labs for analysis, was judged less than average engine wear (oil changes were done at ~8,000mi (12,857km). The report is in my gallery. There final comment was "NIce bike!" And I've never tended to a thermostat. I would be inclined to judge your bike normal. Link to comment Share on other sites More sharing options...
Superballs Posted June 2, 2017 Share Posted June 2, 2017 On 4/9/2017 at 2:33 PM, RolandHTG said: I do not doubt the competency of the Honda engineers but I do believe they make compromises. The 5th gen was based on a V-4 design that was intended to be competitive in Superbike racing. I don't think that parameter quite fits the broader needs of a sport tourer. True I had 145,000 on my 99 but the cooling problems showed up 90,000 miles earlier. Running hard in the Smokie Mountains and then getting stuck in tourist town traffic was too much for the side mounted radiators. I just think they did not get enough air flow. I can vividly recall my frustration watching the temp readout climb as the speed of the traffic I was behind dropped. I'm curious as to what your temps climbed to. I learned very quickly that at 122C (251F) the engine temperature WILL start flashing at you and the black line underneath the termperature reading will disappear to expose the red line that is usually only visible when the engine is off. I've seen some very high temperatures on my bike until I filled/bled my coolant and the hottest I've seen in stop and go traffic is 107C. But as long as it's not flashing, it's good, and the fans seem to do a good job of keeping it from getting too hot. Link to comment Share on other sites More sharing options...
Member Contributer RolandHTG Posted June 3, 2017 Member Contributer Share Posted June 3, 2017 I saw 251 F many times before I installed a manual switch. Once the switch was installed I would flip it on whenever temp went above 210 F. Link to comment Share on other sites More sharing options...
9C1 Posted December 19, 2017 Share Posted December 19, 2017 Old topic, but I'm curious about the manual override for the fan. Are there directions anywhere? My bike is up for the winter and I'm doing a bunch of maintenance on it, so now would be a prime time to do this mod. Link to comment Share on other sites More sharing options...
Member Contributer Terry Posted December 19, 2017 Member Contributer Share Posted December 19, 2017 The thermoswitch on the radiator is completing the path to ground when it closes, so it really is as simple as installing a toggle switch between any good chassis ground point and the black lead that terminates on the switch spade terminal. I would splice into that wire and leave it connected so the thermoswitch can still function if (when) you forget to do the manual thing. Link to comment Share on other sites More sharing options...
Member Contributer Cogswell Posted December 19, 2017 Member Contributer Share Posted December 19, 2017 My fan switch has significantly eased my cooling concerns. Once I inadvertently left it on and wondered why the temp kept rising at speed. It does require some mindfulness to manage it. I installed a dual throw switch which allows me to also turn it off at speed so the fan does not fight the flow as well as forcing it on. After a while it becomes 2nd nature. Definitely a good mod. Link to comment Share on other sites More sharing options...
9C1 Posted December 22, 2017 Share Posted December 22, 2017 Thanks for the help! Much appreciated. Link to comment Share on other sites More sharing options...
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