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Thread: Coolant leak

  1. #1
    Senior Member fastfred's Avatar
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    Cool Coolant leak

    Yesterday I was in climb from Pennsylvania and I could smell hot rubber and the CHT was high but not in the red. Everything else was normal for an 85 degree day. I leveled off right away and it cooled down and the smell went away. I slowly climbed to 4000 where the air was cool and continued 1.5 hours home everything looked good.
    I inspected it before putting it away and found anti freeze spread spit out on the belly and firewall. The resivoir was empty but the filler was almost full.
    I can find no leaks . I wiped it down , refilled and fired it up to operating temp with no leaks . I will let it sit for awhile and check some more.
    I figure I will start replacing hoses and clamps. Is there a thormostat anywhere?

    I appreciate any advice.

    Fred

  2. #2
    Senior Member Dorsal's Avatar
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    Default Re: Coolant leak

    FWIW I had the hose between the reserve tank and the engine split at the connection to the engine side.
    Dorsal ~~^~~
    Series 7 - Tri-Gear
    912 ULS Warp Drive

  3. #3
    Senior Member Dave S's Avatar
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    Default Re: Coolant leak

    Fastfred,


    One idea, (but not the only possibility by any means) : on liquid cooled engines belching out coolant can be the result of the coolant exceeding its boiling point for one reason or another.


    One point to keep in mind, the CHT is not the same as the coolant temperature. The actual temp of the coolant could possibly be higher than the CHT.



    You should be able to determine if a thermostat is installed in your kitfox - if one is there (most don't use a coolant thermostat) it would be in line in one of the two 1" hoses. I am sure you could confirm or rule that out easily.


    The coolant itself - I think most people are using 50:50 ethylene glycol - often Dexcool which works well. If the coolant is diluted - it would boil at a lower temp. If it is Propylene glycol (Evans) it should be full strength - not diluted.


    Pressure cap. If the pressure cap does not hold the specified pressure on the system, a defective cap normally will result in a lower boiling point of the coolant.


    Then there is the radiator; which must be in good condition and not plugged up with bugs and junk from the outside or dirt/sediment on the inside.


    Hoses - A defective or weak hose can collapse on the suction side reducing coolant flow - probably not a common cause of anything since the system pressure will normally ovepower any tendency to collapse.


    Don't know; but, at least a couple thoughts.
    Dave S
    Kitfox 7 Trigear (Flying since 2009)
    912ULS Warp Drive

    St Paul, MN

  4. #4
    Senior Member rv9ralph's Avatar
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    Default Re: Coolant leak

    Here is another possibility. If you changed coolant recently, air in the system can cause coolant to go out the overflow. The system will want to suck in more coolant as it cools, which is normal, if the overflow bottle is empty, it will get more air back in. The air expands more than the coolant when hot.

    Ralph

  5. #5
    Senior Member Wheels's Avatar
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    Default Re: Coolant leak

    I zoomed out of my field on a hot day, I pulled up to VX and held it for a full minute. Suddenly lots to steam in the cockpit, the bottle had split under the cap and leaked coolant down onto the hot manifold, oops.

  6. #6
    Senior Member fastfred's Avatar
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    Default Re: Coolant leak

    Quote Originally Posted by rv9ralph View Post
    Here is another possibility. If you changed coolant recently, air in the system can cause coolant to go out the overflow. The system will want to suck in more coolant as it cools, which is normal, if the overflow bottle is empty, it will get more air back in. The air expands more than the coolant when hot.

    Ralph
    Is there another overflow that doesn't go back into the tank?
    The only place I can find is where it might have blown past a clamp on the pump.

  7. #7
    Senior Member fastfred's Avatar
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    Default Re: Coolant leak

    [QUOTE=Dave S;74804]Fastfred,


    One idea, (but not the only possibility by any means) : on liquid cooled engines belching out coolant can be the result of the coolant exceeding its boiling point for one reason or another.


    One point to keep in mind, the CHT is not the same as the coolant temperature. The actual temp of the coolant could possibly be higher than the CHT.


    Don't see any thermostat. What keeps it from overheating? How would you know if the cht not an iducator?
    It appears it blew past a clamp.
    How about the coolant pump do they go bad and what would it do?

  8. #8
    Senior Member jiott's Avatar
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    Default Re: Coolant leak

    What keeps it from overheating is a properly sized radiator and oil cooler. A thermostat only helps from overcooling. Most of us don't have an actual coolant temp readout, but if either the CHT or the oil temp gets close to the redline, you have a problem and need to figure out the cause. Most likely an airflow restriction thru the radiator/cooler, a partially clogged radiator/cooler, a kinked oil line, a collapsed radiator hose, low coolant/oil level. Its pretty rare for a coolant pump to completely fail; usually the seals go bad first and you will notice leakage and loss of coolant.
    Jim Ott
    Portland, OR
    Kitfox SS7 flying
    Rotax 912ULS

  9. #9
    Senior Member fastfred's Avatar
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    Default Re: Coolant leak

    Thanks Jim
    I am trying to duplicate the climb and test it. I guess it was a combo of High heat , high RPM, high weight and most likely high density air.
    I lost a quart of coolant but I can't see where it came from is my problem. I think the leaked stop once I leveled off into cool air? Otherwise I was diverting
    I am going replace the hoses and clamps first. We are guessing they are original and I will clean out the radiator . How about that synthetic coolant rotax recommends? The radiator doesn't look that dirty but this is a new plane to me so who knows if it was ever cleaned out or how old the hoses are. I could smell a hot hose was the only thing that told me there was a problem.

  10. #10
    Senior Member jiott's Avatar
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    Default Re: Coolant leak

    The waterless coolant Kitfox used to recommend is now definitely NOT recommended by them. If that is what is in your system, it needs to be properly drained and cleaned out, and refilled with Dexcool 50/50 anti-freeze. You will find your temps will drop 10-20F.
    Jim Ott
    Portland, OR
    Kitfox SS7 flying
    Rotax 912ULS

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