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Help MC19 Overheating. Whats going on?

Discussion in 'Honda 250cc In-line 4's' started by Revolver, Mar 10, 2017.

  1. Revolver

    Revolver Big Member Premium Member

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    So, I have put my brothers MC19 on the road (been meaning to do the thread), but have come across some heating & cooling issues.

    Before putting it on the road, we filled the cooling system.

    After 2 weeks of it getting to midway to high on the "P" in traffic & generally between the E & M on the highway, I pulled out the thermostat & boiled it alive to see if it was functioning. It was not. Meant to open @ 82deg apparently. I also noted the coolant system wasnt full.

    In my wise choice after ringing a number of Honda dealers trying to source another & being told it was listed as "NLA", I took to it with the dremel, chopping the housing in half & removing the back half, & putting in the restrictor back in to regulate the flow. Dumped the coolant & put some fresh stuff in.

    This instantly improved the cooling effect as thought. And on the way to & from work was awesome. Bike stayed cool Staying at "E" on the highway, high "M" in the traffic. A noticeable improvement.

    On the way back on Wednesday, I noticed coolant coming off the fairing & hitting my boots & pants, & realised that I hadnt done up the top clamp to the thermostat housing. (Due to me dropping everything to attend to a urgent family medical emergency while re-assembling, so I couldn't follow my re-assembly checks & procedures I do before putting major components back on). I new immediately that was the one thing I was yet to check when I saw it leaking.

    Nursed the bike home on "M" the whole way.

    Did the clamp back up, (that was an effort) put some more coolant back in, not much was missing. Checked for other leaks & came up with nada.

    Went to work & got pulled over by another bloke on a bike telling me I'm leaking fuel, (turns out coolant from the overflow pipe) & put it down to me over filling the system. But she got hot in traffic again. Almost passed the P & into the red when I parked up to work.

    On the way home, it got hot fast, hot in traffic, on the highway cool as a cucumber. Barely nudging the E, dropped into the supermarket, temp skyrocketed to the P instantly. Turned the bike off, listened for the fan, nothing. It was working before I would always hear it before switching off the bike.

    Riding home for a few Ks got some airflow & it stayed at M, rolled into the driveway waited for the door to open, stayed at M, nudged P when I switched it off, ignition of to check fan, nothing.

    So, whats up? Did my bogan spec thermostat mod stuff up the whole shebang? Surely its not the temp switch for the fan as well? And surely the system doesnt redline after sitting at lights for 30 seconds without the fan on.

    The bike I assume was running with lower than recommended coolant for 2 weeks prior, getting hot but not totally overheating. Was still cool when it was full but leaking. But the moment everything is done up & full it overheats? WTF?

    Do I have a misunderstanding of thermal dynamics & the cooling system of an MC19 is actually better with a less than full system?

    So if it is turned on by the thermostat, where do I get a new & proper functioning one?

    What is going on? I'm stumped.
     
  2. Murdo

    Murdo The Good Doctor Staff Member Contributing Member Ride and Events Crew

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    Are you sure the wire to the thermo fan switch didn't get knocked off while you were working on it? What about your fuses?
     
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  3. Revolver

    Revolver Big Member Premium Member

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    Those are my thoughts, & next port of call, but surely glycol istelf doesn't heat up THAT much that quick.
     
  4. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Are there any bleed nipple's on the system to get rid of any air?
    You can use a 2 litre bottle with the bottom cut off, wrap the thread with electrical tape and carefully screw it into the radiator filler neck, then fill the coolant 1 litre above the filler neck and run the bike for a while.
    The extra weight of the water can help to force out any air in the system


    Is the fan switch a single terminal type?
    If so is the earth wire to the thermostat housing all good ? eg- goes to clean bare metal (smear with dielectric grease)
    Are the earth lead wire's corroded at all?

    I read on another forum you can use a Tridon thermostat part number TT239-180, or slightly warm one's- TT239-185 or TT239-190
    It has a 44mm o'd and open's at 82 degree's C

    Supercheap sell them for $17.50
    http://www.supercheapauto.co.nz/Product/Tridon-Thermostat-TT239-180/7838
     
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    Last edited: Mar 10, 2017
  5. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    New thermostat for starters !
     
  6. Revolver

    Revolver Big Member Premium Member

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    Well I tried that. However they said there were no genuine or aftermarket ones.

    Turns out there are some tridon ones.
     
  7. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    No coolant shouldn't heat up that quick, but if there's still air in the system it'll make steam and thing's will get real hot real quick
     
  8. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    TT239-180 is the same thermostat as the FZR250 uses.

    When filling the cooling system, the bike must be level. Squeeze any coolant hoses you can reach to 'burp' the system of air - you'll be surprised how much more coolant you can get in, especially considering the small capacity of the cooling system. Make sure you pre-fill the overflow bottle to the 'low' marker. Also if you're going to the trouble of replacing the thermostat, do the radiator cap as well.
     
  9. Revolver

    Revolver Big Member Premium Member

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    Yeah the radiator cap does need replacing in the near future. I'll have to see if there is a direct replacement by tridon.

    As for burping, I did that too. Level squeezing as many hoses as I could. But not much as going down. So the system was full.

    I'm about to wheel it out & start investigating again.
     
  10. Revolver

    Revolver Big Member Premium Member

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    Ok, So I decided to leave this post of the brash claim that all is fixed.

    Drained the coolant, and there was bugger all in there.

    The Cap seal had started to perish, & the last time I put it on killed it. So I went out & bought one, got some more coolant, no thermostat (Supercheap didnt have one), pulled off the radiator, flushed it, cleaned the connections on the fan, bench tested it, cleaned the fan switch connections, & the side to the radiator that was covered in gunk. Filled the bike with water, new cap, freshly cleaned radiator & ran it to hot.

    Though I noticed the fan wasnt running. Onto the P & heading for red, I am about to shut it down, take another look at the fan & something catches my eye. I hadnt re-connected the fan plug after pulling off the radiator (not the problem before). Which cooled it back down.

    Drained it all out, flushed new coolant through it & the filled it ran it to hot, plugged in fanf, it cooled it back down. No problems since. Most it gets to, is mid way M. Hot, not moving in traffic, its all it gets to.

    Great success.

    Thanks for the suggestion guys.
     
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