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Normal Engine Coolant Temp


NeodyTone

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Hi, all!  Brand new to this forum.  Just bought a '99.  Rode at highway speeds with 30F outside temp and the coolant never got over 145F.  Stopped at the gas station and let it idle and the coolant rose to 218F.  Is this fluctuation normal in cold weather?  Thanks in advance!

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176F is where the thermostat should be opening, and under normal riding steadily conditions, the engine should not be below this. Your 145F sounds like you might have a stuck-open thermostat. 

 

Once you stop/go slowly with little airflow, the temperatures will climb pretty fast. The fan should cut in around 212F or a little over that.

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44 minutes ago, NeodyTone said:

Thanks!  I thought that might be the case, just wondered what the range should be.  Hopefully R&R of the thermostat isn't too tough.

 

Unfortunately the thermostat is buried deep in the "V" of the engine, under the Fuel Tank, Air Box and Throttle Body.  Not an easy job but it has to be done, the bike will run so much better afterwards. 

 

5th Gen thermostats always fail (eventually), but they don't all fail the same way.  Some stick open, some stick closed, some develop a sticking (stopping) point short of either full open or full closed (or in between both).  The resulting symptoms are sometimes hard to diagnose as thermostat related.  You've got the most obvious case, and it's the worst case also.  The VFR engine hates running cold.

 

Good luck the the replacement.  My advice (while you've got things disassembled) is to also replace the two short hoses that connect from the thermostat housing to the cylinder heads and replace the O-rings for the cylinder head connections.  I refurbished a '99 a year ago (January-February of 2017), here's a forum thread of my work (with lots of pics and explanations) http://vfrworld.com/threads/refurbishing-my-99-5th-gen.52488/ 

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Greg's advice on the hoses etc is very wise. I would also buy new throttle body rubbers, they will make remounting the throttle bodies easier as they will be fresh and pliable, not too expensive either (around $8 ea IIRC). 

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I just finished mine (literally just sat down in front of the computer after walking in the door).  It's not too bad but it is time consuming.  Order the O-rings for the coolant flanges on the heads too.  Mine were so bad.  I have a thread in here about it.  Look at the pics then go order the parts. 

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If you see *continuous* temps higher than 220ºF or below 180ºF then
trouble shooting is in order:

 

Continuous engine temps above 220ºF or 104ºC is a problem and the proper
order of items to trouble shoot are:

1)Faulty radiator cap... system should hold 1.1 pressure ratio...
2)Insufficient coolant...
3)Passages blocked in the radiator, hose or water jacket...
4)Air in the system...
5)Thermostat stuck closed...
6)Faulty temp meter or thermo sensor...
7)Faulty fan...
8)Faulty fan switch...

 

Engine temps below 180ºF or 82ºC is an problem... it means that the
moisture produced during combustion is not getting hot enough to
evaporate out the pipe as steam... instead that moisture will migrate
to the oil and produce a milky white contamination...

Note normal by products of combustion is water... . Every gallon of gas
creates roughly 8 pounds of water vapor... we all have witnessed water
escaping out of tail pipes on cold mornings...

The sequence of events to trouble shoot are:

1)Faulty temp meter...
2)Thermostat stuck open...
3)Faulty fan switch... (stuck on)

 

On bike Thermostat Check

To check if the thermostat is opening start the engine at its lowest
temp... open the rad cap... observe at what temp the coolant begins to
flow... normally it should flow close to 180F...

 

 

 

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  • 2 months later...
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Not the original poster, but also a fairly new to VFRs.  My fifth-gen ('98) is making what seems to me an unusual noise: As I slow to a stop, I hear a sound like fluid and air being blown out or sucked into a straw. Sort of a gurgle, but with definite non-liquid bypass.  This occurs regardless of indicated engine temperature during my commute.  It may make the sound while I am underway, but I only hear it when stopping.  Not tire/brake/chain movement related, as i can here it after I am at a complete stop.  Not a constant sound either, it will gurgle and blow, and then no noise.  Does this sound like a particular problem in the cooling system?  (with 90 degrees F ambient temperatures, the engine temp climbs steadily to 218 degrees F over the course of a 25 minute commute at speeds between 40 and 25 mph).  No visual indication of coolant leak.  35,000 miles on the odometer.  Thanks in advance!

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Perhaps there is air in the coolant system? When it's cold, park on the side stand and remove the radiator cap. Being on the side stand makes the rad cap the highest point in the system and should allow the air to rise to that point. If you can't see any coolant, fill it up. If you do have coolant, run it for a brief time to circulate it. It won't take long to heat up the coolant and cause it to expand, so don't run it long without the cap.

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An odd noise that the 5th gen can make is caused by the vacuum operated flapper valve on the airbox, specifically when stationary or nearly. I thought I had an electrical arcing sound initially, turned out to be the solenoid for the flapper cutting in/out due to the clutch switch making intermittent contact. If you have aftermarket levers these can be adjusted so that when pulled in, the clutch switch is not quite fully closed, that causes the solenoid to cycle on/off and makes the vacuum flapper do the same. That will only happen in gear because (and I don't know why) the ECU is programmed to open the flapper with the clutch pulled in when in gear, but in neutral the flapper is always open irrespective of the clutch switch.

 

You can check whether this is your source either (1) disconnect the clutch switch (you won't be able to start the engine in gear, but all else will be normal) or (2) disconnect the flapper by pulling the hose off the actuator (and plugging that) or (3) disconnecting the solenoid (hard to do, buried under the airbox). 

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Possible air in the coolant system was an easy thing to check, and I did follow the manual recommendation to "burp" the air out.  I noticed the smaller of the two seals on the radiator cap was fouled up with some crud, so I cleaned it and checked the surface it seals against to make sure there wasn't anything crusted there.  The seal looked bad enough to me even after cleaning that I doubt it will seal welll, so I have a new radiator cap coming.  But the second possibility!   I did just switch out my stock clutch and brake levers, so I will also take a close look at the clutch switch interaction and the associated flapper. 

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  • 2 weeks later...
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Following up for the curious; After "burping" the coolant system, I replaced the radiator cap with a new one.  I also checked the switch that gets activated by the clutch lever.  My new aftermarket levers do not touch the switch when they are adjusted closest to the grip, but do make good contact at any of the other settings.  I did remove the switch and cleaned the contacts, then re-installed and adjusted to the middle setting.  The strange sound did not recur during a test ride or my morning commute, even when I adjusted the clutch lever to miss the switch.  So, I think the problem was a damaged seal at the radiator cap. 

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