Engine Drivetrain 1st Gen Cooper S Most liked posts in thread: Tensioner: Why so scored?

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  1. CHKMINI

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    #2 CHKMINI, Oct 31, 2012
    I think those are sound wave marks caused by high decibel exhaust levels :)
     
  2. Crashton

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    #6 Crashton, Oct 31, 2012
    Warning this contains a serious thought

    Here is what I think. I know I'm a smart arse, but this is a rare serious moment.

    ***Rare serious thought***

    I think it is possible that was cause by swarf. Pieces parts left over from the machining process. Either from the rebuild or possibly from the manufacturing of the tensioner. It does not take much to score up a piece like that. In my opinion that was not caused by the type of oil, just some junk in that oil.

    If you do not have a magnetic drain plug I'd install one. I'd also do a few short mileage oil changes just to make you feel better.

    I think Gnat will be all right. :Thumbsup:
     
  3. Nathan

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    #19 Nathan, Nov 1, 2012
    On the top of the cylinder the marks show it was spinning. Look at the one that has 100k miles, on the top you see it has a single wear mark. Now look at mine that just came out of the car. You will see that there is a faint circle on the top wear the manufacturing grinder marks have been worn away.
     
  4. Steve

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    #20 Steve, Nov 1, 2012
    I think Jason is right though. Yes, the piston was rotating so you see a pattern of score marks around the circumference of the piston and a circular wear ring on the end of the piston. But it looks to me like the individual score marks / scratches are vertical, aligned with the compression motion of the piston.
     
  5. Crashton

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    #24 Crashton, Nov 1, 2012
    :ihih: :postcount
     
  6. Nathan

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    #25 Nathan, Nov 14, 2012
    Might have fixed this today with the help of Jan, Chad and Anson of Best Motor Werks.

    The rattle was back and really bad. Doing some more investigating it was determined that the head was decked at the last rebuild, but only 0.002 was removed. Not enough to really make a difference. However, that's not the first time it was decked and the amount shaved off in total is not known. The brain trust was thinking the tensioner did not have enough reach in it to pick up the slack. Since it had been making the noise on startup for some time it was also determined that there may be wear on the plastic chain guides too.

    We thought it might be best to give the tensoner a bit more reach before going in and replacing all the guides, sprockets and chain. Figuring it could be an inexpensive fix if it worked.

    So...how to give the tensioner a bit more reach? A washer!

    [​IMG]

    So far, so good. No more chain rattle.

    I tell ya, it's great to work with people and shops that think outside of the box. Try to get a dealer service dept to add a washer like that.
     
  7. BThayer23

    BThayer23 Well-Known Member

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    #3 BThayer23, Oct 31, 2012
    What kind of oil do you run? And do the score marks line up with full compression or somewhere in the middle? Is the tensioner hydraulic or is there a spring inside?
     
  8. Nathan

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    #4 Nathan, Oct 31, 2012
    Since the rebuild up until this latest oil change it has been Royal Purple. The last oil change not more than a hundred or so miles ago at best was Motul.

    The marks are at a point where the tensioner is barely pushed in.

    No idea if there is a spring in there or not. Possibly as one can push it in and it pops back out, most of the time.
     
  9. Dave.0

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    #5 Dave.0, Oct 31, 2012
    Could be low on washer fluid. :confused::lol:

    I run Amsoil and have had no issues for 50k plus now.
     
  10. Dave.0

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    #7 Dave.0, Oct 31, 2012
    But I thought almost all Mini parts were good for a lifetime of service....:lol::ihih::lol::devil:
     
  11. Nathan

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    #8 Nathan, Oct 31, 2012
    I do have a magnetic drain plug. I did look at the amount of crud on it at that the last oil change. I'd seen worse in this engine. Sorry, I neglected to take a picture this time.

    This is from engine after the first oil change that was preformed after the Dimple Magnetic Drain Plug was first installed. This last oil change had less than this image shows.

    [​IMG]

    I'm not at all discounting the "swarf theory" Chad and I discussed this possibility way back when the first tensioner failed after the rebuild.
     
  12. Crashton

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    #9 Crashton, Oct 31, 2012
    Well check that one off. :Thumbsup:

    I know your engine was built with utmost care. I'm not laying this on Chad at all. Stuff like this just happens from time to time. That tensioner has a spring inside, but uses oil to maintain tension on the chain. My guess is that thing stuck in causing the timing chain to gain slack & skip the teeth.
     
  13. lotsie

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    #10 lotsie, Oct 31, 2012
    Have to agree with Crashton, sounds like crud was in the part when it was installed, luck of the draw.
     
  14. AnsonIvan

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    #11 AnsonIvan, Nov 1, 2012
    More notes and pictures on the tensioner adventure, I performed this latest tensioner replacement. I found the tensioner almost fully compressed with the piston protruding about 3mm. When compared to a new tensioner Gnats part felt nearly identical, that is to say somewhat crunchy in its compression stroke.

    I compared the roughly 6,000 mile tensioner with a 100,000 mile unit and found no scoring on the high mileage unit. The high mileage part also has a defined wear spot on the engagement face of the piston where it was contacting the tension rail. Gnats part was clearly spinning in the bore and had a light wear ring where it contacted the tension rail.


    Left = new, center = gnats, right = high mileage part
    [​IMG]

    Rotation vs. stationary
    [​IMG]

    High mileage part
    [​IMG]
     
  15. Herleman

    Herleman New Member

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    #12 Herleman, Nov 1, 2012
    Improper hardening of the original part, or extreme temperature while in use?

    To me it just looks like Gnat's piece was not as well hardened.
     
  16. Metalman

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    #13 Metalman, Nov 1, 2012
    Crunchy operation of a new part seems to be a problem....
    Should the piston rotate.... or not?
     
  17. Nathan

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    #14 Nathan, Nov 1, 2012
    I've been told it is not supposed to rotate and that the markings that the high mileage one Anson posted a picture of is normal.
     
  18. ZippyNH

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    #15 ZippyNH, Nov 1, 2012
    Any chance it was a defective batch/counterfeit part?
    Might want to have the re-builder ask his part supplier...
    My one thought is that since the Gen1 Tritec motor plant was dissembled, and sold to China, where it is still churning out TRI-Tec motors for a pair of Chinese only consumption makes.......some NON-MINI supplied parts might be cheap Chinese parts, that were supposed to be used in CURRENT production motors...undoubtedly a much lower quality than when MINI/BMW and Chrysler were involved....
     
  19. Nathan

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    #16 Nathan, Nov 1, 2012
    The part came from a MINI dealer.
     
  20. BThayer23

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    #17 BThayer23, Nov 1, 2012
    What would cause the piston to spin? Vibration? Weak spring?
     
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