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Thread: 1985 K100RS. If it weren't for bad luck........Y'all know the rest of that one.

  1. #1
    Registered User mcmlcccvrs's Avatar
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    1985 K100RS. If it weren't for bad luck........Y'all know the rest of that one.

    I just don't understand why, oh why, I cannot find a non-leaking 3-core used rad. I swear the BMW gods are out to get me. I have a solid 2-core that I use, but I JUST CANNOT find a good 3-core. The area where the plastic tanks are crimped to the metal core seem to be a problem. I know that BMW went to 2-core rads, but still.........

    If my 2-core starts to suffer incontinence, and given my rotten radiator ruck (Scooby-Doo impression), I'll probably have no choice but to go straight to an aluminum rad.

    Rant off!
    Last edited by mcmlcccvrs; 01-24-2023 at 08:23 PM.

  2. #2
    ?

    eBay has NEW radiators for 100 bucks.

    https://www.ebay.com/itm/29549006103...Bk9SR6rTw-W8YQ

    Why not use one of those?
    -Live as fully as you can as long as you can-

  3. #3
    Registered User mcmlcccvrs's Avatar
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    Quote Originally Posted by OldCamper View Post
    ?

    eBay has NEW radiators for 100 bucks.

    https://www.ebay.com/itm/29549006103...Bk9SR6rTw-W8YQ

    Why not use one of those?


    Thank you for the link. They don't ship to Canada. Also, if the image shown is accurate in detail, they have the two lower mounting points upside down. They are suppose to be curved arms that rest on top of the rubber lower bush mounts, not hooks that go underneath.

  4. #4
    About 100 years ago I pried open the crimped edges of the radiator end caps and removed them. Right now I can't remember why, but I do remember doing it. Resealing the ends with some high temp sealant and recrimping might cure your problem.

    Frank
    '17 R1200RS, '03 R1100S BCR#6/200, '85 K100/1100RS, '16 R1200RS (gone) '11 R1200RT (gone) '05 R1200ST (gone) '99 R1100S (gone) '96 Ducati 900SS/SP (gone) '92 K100RS (gone) 500,000+ BMW miles

  5. #5
    Registered User mcmlcccvrs's Avatar
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    Quote Originally Posted by 51797 View Post
    About 100 years ago I pried open the crimped edges of the radiator end caps and removed them. Right now I can't remember why, but I do remember doing it. Resealing the ends with some high temp sealant and recrimping might cure your problem.

    Frank

    Frank,

    Thanks for the suggestion. I actually talked to a local rad shop about leaks in this area, and the first thing the guy said was to buy a new rad. He also said that automotive rads of the same construction suffer the same failures. They can re-crimp if for me with no warranty, but that the re-crimp actually weakens the metal tabs. It sounds like you have had success with what you did. I'm just getting tired of going in circles. I'm getting closer to the hard reality that the only real, long-term solution might be an all-aluminum, aftermarket rad.

    Thanks,
    Tom

  6. #6
    3 Red Bricks
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    Tom,


    If you notice, all the Chinese made aluminum radiators advertised on ebay seem to be made by the source. There are multiple people (companies) in the LA area selling them for around the same price. I had a bad experience with one of them several years ago. I purchased a radiator for my ‘89 635. It showed up quickly and looked beautiful! Unfortunately, The transmission cooler lines were the wrong size. And the lower radiator hose fitting was the wrong size. And the drain was on the wrong tank. Oh, and the upper radiator fitting was pointing in the wrong direction, and was too small. Other than that, it was really pretty!

    After much hassle, and having to get ebay involved (with pictures and dimensions and records of all correspondence with the seller, I finally got my money back (minus return shipping on the oversized package) about 2 1/2 months later. Buyer beware!



    On a brighter note;
    I found this this morning: https://www.ebay.com/itm/28512290278..._e9YQ#shpCntId

    Parts fiche says it is also the correct radiator for your bike:

    https://shop.maxbmw.com/fiche/PartsS...17111464568%0A

    It only has 12,000 miles on it and they ship to Canada.





    Last edited by 98lee; 01-26-2023 at 08:51 PM.
    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

    Lee Fulton Forum Moderator
    3 Marakesh Red K75Ss
    Mine, Hers, Spare

  7. #7
    Registered User mcmlcccvrs's Avatar
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    Lee,

    Thank you for the link. That is a 2-core rad and it will fit my bike as that is what I am currently using. Unfortunately my luck on the used radiator market is dreadful.

    I am looking into an aluminum rad from KParts Holland. I am just waiting to hear back from him on a couple of questions I have.

    He says, "This radiator will replace the original radiator of every K75RT, K100 and K1100 model."

    https://kpartsholland.com/collection...ew-17111464569

  8. #8
    3 Red Bricks
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    Tom,


    What model and year did the 3 row radiators originally come in?

    When you get the aluminum one, let us know your impressions.




    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

    Lee Fulton Forum Moderator
    3 Marakesh Red K75Ss
    Mine, Hers, Spare

  9. #9
    Registered User mcmlcccvrs's Avatar
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    Lee,

    The K1100's came with 2-core rads. The same plastic side tanks were used, but as there were only 2-rows of coolant tubes (same number of columns), the radiator core was thinner. When installing a 2-core, a spacer needs to be used between the top, rear of the rad and the bikes frame where the top mounting bolt goes in. The 2-core also dispensed with that foam piece (BMW calls it a gasket) that spans the top of the rad used on 3-cores. You won't see it in the parts fiche for the K1100's. I cut one to fit for my 2-core. I really don't know what the purpose of that piece is anyways.

    With regards to that foam piece on the top of the rad. It doesn't appear in the parts fiche for the 1989-92 4V K100RS. Does that mean they switched over on that model? Someone will know.

    If I move forward on the aluminum rad, I will most certainly do an update (I'll start a new thread) with photos.


    Cheers,
    Tom

  10. #10
    My June 1985 Production date K100RS has a 3-row radiator. That's all I know,

    Frank
    '17 R1200RS, '03 R1100S BCR#6/200, '85 K100/1100RS, '16 R1200RS (gone) '11 R1200RT (gone) '05 R1200ST (gone) '99 R1100S (gone) '96 Ducati 900SS/SP (gone) '92 K100RS (gone) 500,000+ BMW miles

  11. #11
    Registered User mcmlcccvrs's Avatar
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    Quote Originally Posted by 51797 View Post
    My June 1985 Production date K100RS has a 3-row radiator. That's all I know,

    Frank

    As did my 03/85 build K100RS.

  12. #12
    I ordered one of these $99 (including shipping) ebay aluminum radiators to have as a spare for my K75S bikes.

    https://www.ebay.com/itm/29549006103...Bk9SR6rTw-W8YQ

    In an earlier thread I described my fix of a leaking K75S radiation. I ordered an old radiator from ebay, just in case my repair attempt was unsuccessful. The repair was successful, but as I have several K75S bikes and plan to keep them for ever, I thought an inexpensive new radiator would be useful. The link to the earlier thread on my repair is below -

    https://forums.bmwmoa.org/showthread...-radiator-leak

    After seeing comments above I was expecting to need to return this new $99 radiator. I opened the box and made several photos of the new radiator along side the used K75S radiator. Photos below. I think that I will keep this new radiator!

    2rad1.jpg
    2rad2.jpg
    2rad3.jpg
    2rad4.jpg

  13. #13
    Registered User mcmlcccvrs's Avatar
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    Robsryder,

    Thank you for the photos showing the comparison. Unless my eyes deceive me, I don't see how the aluminum rad will fit correctly, as your photos show it to clearly be wider. While it looks like you can fit it as the OEM mounts, how is the rad hose from the water pump to the neck of the rad below the thermostat housing suppose to fit on? In your photos, the aluminum rad looks to be at least a couple of inches wider. The neck below the thermostat housing for the water pump hose needs to be directly over the hole in the crankcase cover.

    Also, if the rad is wider, the OEM hose running across the rear of the rad will be too short and the hose from the filler neck to the the top right of the aluminum rad will be too short also. Have you done a test-fit?

    Or am I missing something here?

    Tom

  14. #14
    I have not done a test fit on either the used ebay radiator or the new aluminum radiator. The repair on my original radiator was successful and unless it fails or other issues arise, these "extra" radiators may never be used. My K75S bikes have somewhat flexible rubber radiator hoses. I was able to re-use the OEM hoses when I did my repair, but I obtained a new set of hoses for the future.

    I did modify the radiator fan and motor shaft on all of my K75S bikes (and an extra on the shelf) to preclude future occurrences of the failure that initially occurred.

  15. #15
    Registered User mcmlcccvrs's Avatar
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    Quote Originally Posted by robsryder View Post
    I have not done a test fit on either the used ebay radiator or the new aluminum radiator. The repair on my original radiator was successful and unless it fails or other issues arise, these "extra" radiators may never be used. My K75S bikes have somewhat flexible rubber radiator hoses. I was able to re-use the OEM hoses when I did my repair, but I obtained a new set of hoses for the future.

    I did modify the radiator fan and motor shaft on all of my K75S bikes (and an extra on the shelf) to preclude future occurrences of the failure that initially occurred.

    Okay. Fair enough. I've just measured my 2-core which is currently out of the bike-it is from a K1100RS. It only differs in dimensions from my K100RS 3-core in the core thickness, as one row was deleted. The maximum overall dimensions are identical because the the 2-core and 3-core used the same plastic tanks on the sides. Imagine placing the rad in a cube, shrinking that cube in its 3 dimensions until contact was made anywhere and then measuring that. Those would be maximum dimensions at any point. My ruler is in inches and here's what I got:

    Width (left to right as if installed): 18" This is from the outer edge of the thermostat housing, across the rad to the outer edge of the rad hose neck on the opposite tank.
    Height (top to bottom as if installed) 10 7/8" This is from the outer edge of the top rad mount to the lowest edge of the rad hose neck below the thermostat housing.
    Thickness (front to back): 4" without thermostat housing cover. So add another 1/4" for that, let's say?

    See the photos at the bottom of this post.

    I then clicked on your link and went to the aluminum rad out of California and thought it easier to just cut and paste the overall dimensions they state in the eBay listing, which is:

    418mm(H)X270mm(W)X115mm(T)

    So that's 16.4567" x 10.6299" x 4.52756"

    What they call height, which must really be width, is 1.5" less than mine. However, your photos show it to be wider. A couple of things need mentioning. Where are they measuring from? Is a K75 radiator smaller than a K100's? Someone here will know the answer to that. I have no clue as I've never seen one or the bike for that matter. The K75 radiator is a different part number than a K100's, so.........

    Would you be willing, or able, to measure your aluminum one? I'd be interested to know how its dimensions compare to how I measured mine. Photos below!




    Last edited by mcmlcccvrs; 01-28-2023 at 08:21 PM.

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