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Thread: 1992 K75S Coolant Leak

  1. #1
    dwfk75
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    Dec 2009
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    massachusetts
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    1992 K75S Coolant Leak

    Doing winter maintenance, I drained the oil, removed the oil pan for cleaning and removed the oil filter. The next day there was a small puddle of coolant under the engine. It's not coming from the weep hole but from up above where the oil filter screws on. Can't see where it's coming from. Water/oil pump, head gasket?
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  2. #2
    dwfk75
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    Dec 2009
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    massachusetts
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    After some investigation, where the crankcase lower section bolts to the block is an o-ring for the water passage. I believe this o-ring has failed. It's right where the leak is coming from. I can't see anywhere else it could be coming from. Will be taking it apart and replace it.

  3. #3
    Thanks for sharing that observation. I didn’t know about that o ring and I wonder how many of us k75 owners have such a leak but don’t know it. Was there any evidence in the oil that drained out (like a milky color)? I would be interested to know how it goes with the O ring replacement.
    1990 K75s, 2001 R1100RT

  4. #4
    dwfk75
    Join Date
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    I really didn't notice any coolant in the oil when it was drained. I've had the bike for 13 years and do oil and filter changes every year. Every couple of years I pull the oil pan off for cleaning and inspection. Never saw this before. If I hadn't left the oil pan off overnight I would have never known it was leaking. Almost ready to take things apart, had some other projects to do like getting my F650GS ready for the season. After it's apart I'll post some pictures.
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  5. #5
    Thanks for the info, I was planning on removing the pan for cleaning it. Just got this 35 years old K75S for a couple of months and I'm in a total ground up restoration.

    Also restoring a 1989 K75C that I've also got for a couple of month too. Why two K75 ? Long story...

    You have a really neat setup to work on the K75 and what looks to be a very nice blue K75, but we all know the red ones are faster !

    Take care !

    Ignace

    PS Pictures of the K's as of march 2022
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  6. #6
    Nice maintenance setup there! Ok good luck on the work and yes please let us know how it goes.
    1990 K75s, 2001 R1100RT

  7. #7
    dwfk75
    Join Date
    Dec 2009
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    massachusetts
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    Update on coolant leak. Got everything taken apart, all this for a o-ring. Now to put it all back together.
    Attached Images Attached Images

  8. #8
    Thanks for the update and the pics….looks like you’re doing some really good work there. Can that O-ring be accessed by “just” removing the oil pan?
    1990 K75s, 2001 R1100RT

  9. #9
    dwfk75
    Join Date
    Dec 2009
    Location
    massachusetts
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    To remove the oil pan, the transmission has to be removed to get at bolts. For me, removing everything and flipping the engine over makes working on it easier. I made a wooden jig on a dolly for the engine and trans.IMG_5034.jpgIMG_5064.jpg

  10. #10
    Fortis Fortuna Adiuvat Omega Man's Avatar
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    I like seeing someone tear into a pretty complicated repair and figure it out.
    OM
    "You can do good or you can do well. Sooner or later they make you choose." MI5
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    2009 F800GS 1994 TW200

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