Coolant from overflow tank

Discussion in '1st & 2nd Generation 1983-1989' started by Scott S, Sep 15, 2017.

  1. Scott S

    Scott S New Member

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    I put an '85 VF500 back on the road last year. Did a full tune up, all fluids, all the normal "sitting bike" stuff. The radiator was removed and flushed. The drain plugs on the cylinders were pulled at that time, etc. Filled and "burped" the radiator, checked again after the first long ride and topped off coolant to the marks in the overflow tank, per the manual.



    Bike looks and runs great. Fan works, no signs of over-heating ever. I put several hundred miles on it with no issues. A couple of months ago I rode up to a breakfast meet. Long trip on the highway. Just after I arrived...about enough time to remove helmet and gloves...there was coolant coming out of the overflow hose. I thought it was odd, but figured the long stretch of highway had something to do with it, maybe?

    Rode a couple hundred more miles over the next few weeks. At least a few tanks of gas. Last night, I rode up to a local bike night and the same thing happened again. Removed seat and side cover and checked and the overflow bottle eventually found a level; maybe a quarter inch above the "LOW" mark.





    Did I miss something? Is it just "finding it's level"? Is there a bleeder or anything to remove excess pressure from the system? Why the two random "pukes" from the coolant tank? Why did it wait to do it?
     
  2. Captain 80s

    Captain 80s Member

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    If you filled it to the upper mark when cold, it is probably just finding it's level. But... I would def keep an eye on it. And the 500s run hot, so you might consider eventually installing a toggle in parallel to the thermo switch so you can turn the fan on sooner.
     
  3. 34468 Randy

    34468 Randy Secret Insider

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    Watch your temp gauge as well. You could be sitting with a worn out thermostat which could cause this bike to run hot and therefore overheat. Another cause for over heating could be a worn radiator cap. Periodically they do need replacing. I think I have replaced mine once.
     
  4. Scott S

    Scott S New Member

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    I think I filled it to the upper mark, ran it and then installed the cap. THEN I rode it a checked the level afterward and added to the upper mark. It may have been hot when I filled it to the upper mark.
    The fan does work and I've never seen the temp gauge get much past halfway, and that was while sitting in traffic. As soon as I was moving again it dropped back off. It was nowhere near the halfway mark the other day when it puked. It was resting somewhere near that little step or jog on the scale at the time.
    I will take a closer look at the cap, too.
     
  5. squirrelman

    squirrelman Member

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    replace rad cap ;);)
     
  6. MFTIC

    MFTIC New Member

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    Same happened to me. Some awesome person on here mentioned the radiator cap. The more i thought about it the less it made sense. Hasn't leaked again since the new cap though. LOL!
     
  7. Scott S

    Scott S New Member

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    Replaced the cap yesterday and tried to "burp" it.
    It got really hot.... hotter than it EVER gets on the street....and I noticed that the fan didn't turn on.
    Long story short, the thermo switch in the radiator is bad.
    I believe it was a combination of things; old radiator cap, probably some air still in the system, and the switch being bad. Fan is good and runs when supplied with 12V.
    I have a new switch on order and I will drain and flush the system again. Bleed it properly, using some tips I found here and on the Facebook group, and install the new switch. That oughta get it.
     
  8. jeremyr62

    jeremyr62 New Member

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    The VF500 will boil its coolant with no trouble at all even with a working fan if you let it idle for too long. A simple wire to short the fan switch is essential if you are working on the bike, like balancing carbs for example. A defective fan switch would give the symptoms you encountered.

    I have datalogged the coolant temp on a ride, and the rate the temperature increases when stopped at the lights is amazing.
     
  9. Lint

    Lint Member

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    Change your cap. If this doesn't fix it, you have a problem, but always try this first! TRUST ME! I've crashed from coolant getting on the back wheel. It's cheap! Like $8 at AutoZone. I'll even give you the part number:

    20170922_191510.jpg
     
  10. ats1080

    ats1080 New Member

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    I know this is a super old post, but I picked one of these up and it doesn't fit an 86 VFR 700. The retaining tabs are the right size but the outer dimension is too small.
     
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