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  1. #41
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    Yes | No

    Replacement o-rings may be available

    I think Rajaie would agree that the inner elastomer o-rings are the ones that fail. The outer teflon rings probably don't change shape or size very much, so if the inner supporting/compliant o-rings could be sourced this might work fine. I have a VANOS o-ring that I keep meaning to measure and guess what size it used to be. One difficulty is that removing the teflon rings is tricky without damaging them since they have tobe stretched quite a bit to get them out of the groove. Teflon does have a good 'memory' though so they will probably be fine if they don't get any nicks.

    I think Viton would be a good material given the heat and oil, but I'm not expert - does anyone know what would be best?


  2. #42
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    Inner Circle ©155 since: Jul 21, 2003 edjack will become famous soon enough edjack's Avatar
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    Yes | No

    This whole debacle is unconscionable on the part..

    of BMW NA. The executives of this August organization must undergo injections of periodic Teutonic hubris.

    How can they stonewall something as well-thought-out as this?
    Ed in San Jose. BMW CCA member since 1980 (Nr. 62319).

    '97 540i 6 speed. Build Date 3/97. Aspensilber over Aubergine leather.

  3. #43
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    Might be speaking of a premature post we put out


    I thought about your reference some more and realized you might be speaking of a post we put out a year back. As I noted the replacement of the valve seemed to initially work, but failed again within a day. The post was premature. Here’s a link to it. Elated only for a day! :)
    Rajaie
    528i 5sp 06/00

  4. #44
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    Nope there was another one

    it even had pics of the part that was changed. Sorry, if I can locate it I'll post here or email it to you. It may be of interest. Surprised no one here remembers it but, it was back in 2002 or 2003.

  5. #45
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    Yes | No

    this should be a sticky across many boards.



  6. #46
    RMedure
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    Yes | No

    +2


  7. #47
    RMedure
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    Different seals? Or lighter springs?


  8. #48
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    Dynamic application ...

    I'm not sure I'd be worried about the "dynamic" piece of this application. Is it really moving alot? It seems it is prolly lubricated too.

  9. #49
    RMedure
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    Can somebody put a thermistor there and

    log the temp for a while?

  10. #50
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    Re: V8's have 2 more cyliinders to produce more heat??

    Good info.

  11. #51
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    Looks completely different don't know how it works

    Rajaie
    528i 5sp 06/00

  12. #52
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    Re: Dynamic application ...

    The movement range is about an inch. The DME is constantly modulating the valve to maintain oil pressure in the compartments, so I'm not sure what kind of vibration is involved. You also need to take into consideration that the piston is attached to the camshaft. Thus it's constantly spinning inside the cylinder at half the crankshaft speed.

    This is an unusual application for seals; both rotation and plunging. Loach has mentioned that this double criterion is likely what influenced the double seal configuration.
    Rajaie
    528i 5sp 06/00

  13. #53
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    Re: Can somebody put a thermistor there and

    Good idea, if you could determine operating temperature range, get some accurate dimensions, I think it would be possible to source the O-rings somewhere. It should not be difficult to identify the right material (Viton might be a good choice)

    What could prove difficult is if one (or both) of the rings do not have a round cross section although with some more research, you might be able to find just the right part.

    Just visiting this board from the E24 group, seems like a great bunch of people here!

    Mike

  14. #54
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    AH yes! The spinning makes it dynamic application


    Cheers!
    Robert


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  15. #55
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    Maybe I can help on this....

    Is there any way for someone to send me the bad piston seals the Teflon and rubber o rings. I can get Teflon seals made to spec and same with the o rings. I will also look to see if I have some of them (vanos) laying around to see if I can find a more reliable solution.

  16. #56
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    Yes | No

    +4


  17. #57
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    replace both seals with

    a teflon encapsulated viton o-ring?Nate

    1993 325i
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  18. #58
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    Careful....

    Getting the government involved may just succeed in putting the car on the gross polluters list, forcing all of us (in California at least) to go to a special test station. If we didn't pass, then they would make us fix the car - sending us all to the mechanics for new vanos systems.Nate

    1993 325i
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  19. #59
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    Yes | No

    do you work with seals?


  20. #60
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    On o-rings and seals (long)

    I used to sell seals for a few different companies.

    The reason for two different materials in this situation is that teflon (are we 100% sure it's teflon?) doesn't have a very good memory (depending on the grade, there's PFTE, PFA, FEP, and other materials that DuPont calls Teflon). It 'cold flows', which means that it will deform under pressure. However, Teflon has one of the lowest coefficients of friction available, which is very desireable in a dynamic sealing application. There are a couple ways to combat the tendency to cold flow: you can mix it with fillers, which greatly improves its characteristics, but reduces its lubricity; or you can use a spring back-up. In Vanos case, the rubber o-ring is providing the spring force to keep the Teflon seal tight against the ID of the cylinder.

    A much better seal, although more expensive (probably the reason BMW doesn't use them) is a teflon filled spring energized seal. These seals are machined out of a cylinder of filled teflon. The cross section is more or less a C shape. A metal spring is then etched and placed inside the C shape. Whereas regular teflon would deflect after a short period, the spring energizes the seal and keeps it intact for a very long time.

    Here are some good pictures:

    http://www.tamshell.com/spring-energized-seals.htm

    There may be reasons other than cost that BMW chose the o-ring backed teflon seal, however. And there are more options than this, such as teflon encapsulated viton o-rings.

    I have a friend that is an expert in seals (His job is to design seals, from torpedo propeller seals to massive oil rig seals). I'll see if he has any input.Nate

    1993 325i
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