Hot but not too Hot

Discussion in '1st & 2nd Generation 1983-1989' started by FastCletus, Mar 18, 2016.

  1. FastCletus

    FastCletus New Member

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    Been working on my vf 500 F 1986 for while after It was wrecked and parked for 2 years. Replaced radiator with a used one, added new fluid. I went for my first real ride Wednesday to get things up to temp and flowing. Bike ran hot so I went home let it cool and looked in rad. fluid was low, so I topped off.
    Went out yesterday (ambient temp was 70-75F). The bike ran hot but not all the way to the "H" mark, but darn near close. and it stayed at this mark unless i whacked the throttle and went through the gears. Electric fans turned on and kept it from over heating. I got home let it cool. I assumed thermostat was bad. So I took it out and boiled some water on the stove and put T Stat in and it opened. I let it cool and put it back in water a few times. Put it back in bike and same problem occurs.

    How do thermostats fail? It almost seems the temp on the bike isnt hot enough to open thermostat.

    How do I check water pump to see if its working?

    Radiator seems to be in good shape

    The hoses have pressure when I am riding. I can reach down and feel them.

    ODD thing did happen though. When I was riding through town at about 25 MPH after I had jusy rode 25 miles at 65MPH the gauge went to cold then right back to hot in a matter of a few seconds

    Any ideas?
     
  2. FastCletus

    FastCletus New Member

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    [​IMG]. Here she is


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  3. Outboard John

    Outboard John New Member

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    Any chance that there's an air pocket trapped in the system? Maybe try burping it by squeezing the radiator hoses. Any way to watch inside the radiator (cap off) while it's running at temperature to see that the coolant is circulating? Good luck with your temp issue. The bike looks great by the way! I have a 6th gen but I am a fan of bikes with less fairing like yours. I have the good looking but pain in the ass white wheels on mine, Imo that would be a good look on your bike too. It probably helps that I have a little ocd when it comes to keeping my bike clean. :eagerness:
     
  4. FastCletus

    FastCletus New Member

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    outboard, yes I did run it yesterday with cap off and couldn't quite tell if it was circulating or not. I do know when I started the bike the fluid went down, and then I added more fluid, but when it got hot i turned the bike off and it over flowed.
     
  5. Captain 80s

    Captain 80s Member

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    Our bikes run on the hot side. If it doesn't go into the red and the fans kick on, you are probably fine. Most VF/VFR owners install a toggle switch parallel to the thermoswitch so they can turn the fan on earlier when in city traffic. If the thermoswicth is a 2 wire version, you connect those wires. If it's a 1 wire version, connect to a ground. Keeping the original circuit intact is a good idea in case you forget to turn on the fan.
     
  6. Outboard John

    Outboard John New Member

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    Hopefully someone with more diagnostic prowess will chime in soon. Or "chimp in" as Long likes to say.:playful:
    John
     
  7. Allyance

    Allyance Insider

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    Did you get a new radiator cap or using the one you had? If the system can't maintain pressure, the coolant will boil off at a lower temperature. Check cap an spout for a good seal.
     
  8. FastCletus

    FastCletus New Member

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    Cap seems to be fine. Attached is a pick of where my temp is at idle. It will go all the way to the edge and then I shut it down. I used an infrared thermo on the thermostat and it reads 233. What temp should that stat open up. I burped system. And I was able to watch the fluid pulse so I know it's flowing. ?????


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  9. FastCletus

    FastCletus New Member

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    [​IMG]


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  10. Terry Smith

    Terry Smith Member

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    Sounds like you've already proven the thermostat, but these usually open at around 80C /176F. If it working properly when you start the bike cold, the tstat keeps the coolant in the engine until its hot, then opens to let the hot coolant pass through the radiator. So your radiator should stay stone cold for a few minutes, then suddenly get too hot to touch. If the radiator starts heating as soon as the bike is started, then slowly gets hotter, the tstat is stuck open.

    From your description, it does sound like a radiator cap fault to me, as in the cap is not holding pressure as it should.
     
  11. jeremyr62

    jeremyr62 New Member

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    As pointed out above, these bikes do run hot. If that photo is of the bike just sitting and idling but the fan is turning on and off I doubt you have too much to worry about. If it gets to that while riding, then yes you have a problem. There is a thread on here that describes the operation of the thermostat. It isn't quite as straightforward as it seems. I put thermocouples on the hoses expecting to see a jump in the hose temp as the thermostat opens to the rad but this isn't what happens. The rad is always in the circuit so will start to heat up straight away. The thermostat just restricts the flow to the rad. When the coolant is hot enough the flow into the rad is unimpeded. This is why a stuck open thermostat can lead to the bike actually running too cool on a coldish day.

    Not that any of this helps you. Are you sure the fan is sucking air through the rad and not blowing it through?
     
  12. jeremyr62

    jeremyr62 New Member

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  13. FastCletus

    FastCletus New Member

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    Aha. I haven't got a new cap yet. Does anyone know if you can buy one locally from an auto parts store or do I have to buy from dealer. Flea bay only has used ones.


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  14. Outboard John

    Outboard John New Member

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    Since you like to tinker I'm going to assume that you have a compressor. You might take a rubber tipped blow gun to the over flow tube on the over flow bottle and carefully pressurize the system, whatever the cap is rated, say it's 13lbs, pressurize to that and see if it's holding pressure. Start at a lower pressure and work your way up to its rated pop off. Hopefully this will eliminate the cap, or not. If this checks out fine, I would probably pull the radiator and check that it flows ok if you didn't do it when you acquired it. Best of luck.
    John
     
  15. Captain 80s

    Captain 80s Member

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  16. squirrelman

    squirrelman Member

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    If the cooling system was drained it might need two or three times of topping up (cold) under the rad cap after riding.
    As others have said, replace your rad cap b4 anything else. Also go around and check tightness of all hose clamps on the cooling system as they tend to loosen up over the years when the rubber under them compresses. :grey:
     
    Last edited: Mar 23, 2016
  17. FastCletus

    FastCletus New Member

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    Well I think i got the gremlin. I Happened to have the old rad cap in my box of extras. put it in and ran it for a bout 10 minutes + and temp sat around middle of gauge. which is better than before. Wont know 100% until I ride. Stuck at home for 3 days with a 6 year old and a broken foot. So no ride for me. Thanks to all for your help. IF this doesn't solve problem then I am going to clean out RAD.
    Now off to my next project. Carbs and leaky oil pan gasket!
     
  18. squirrelman

    squirrelman Member

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    So you're sure about that ????????????????? :crazy:

    Listen to the old guys and heed their words ! They've been there way b4 you, Bunky.
     
    Last edited: Apr 19, 2016
  19. FastCletus

    FastCletus New Member

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    Nothing rally new just updated. Got a 59 mile ride in today and temp stayed at or around the "m" mark on the gauge. When I got off freeway temp rose and fans cut on. Temp never got to the overheat stage but it was close. Got back on freeway and temp eventually went back down.
    I cleaned the radiator out with vinegar and flushed it good. Burped the system. It's 70 degrees out I have no idea how this bike will make it in summer when it's 95.
    My next step is to get a new thermostat and replace fluid with water water and see if that helps.


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  20. Captain 80s

    Captain 80s Member

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    I own multiple VF/VFRs, with varying mileage and have maintained cooling systems. They all run on the warm/hot side. The key for me is to wire in a switch as described so I can get the fan going as soon as I hit traffic / slower speeds. If I get that fan going, they will pretty much stay in the middle. In 90 plus weather in traffic, they will get about 3/4 (maybe a touch higher on a couple of them). I have never puked coolant or over heated.
     
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