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S90 Throttle body seal

Posted by gsxtasy, Mar 22, 2016

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  1. gsxtasy

    gsxtasy Proven Member

    660
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    Joined Oct 17, 2002
    Lincoln, Nebraska
    Alright, so after finally getting fed up with my leaking s90 TPS side throttle shaft and temperamental idle, I decided to tear into it. Previously I was under the impression that there were no seals at all in the s90 and only ball bearings on the shaft.

    There is a seal!

    EBm5mvHl.jpg

    The seal is recessed behind the bearing on the TPS side and there is no seal on the throttle cable side. The first thing that I noticed was that the seal is installed backwards for sealing boost into the engine. I'm guessing yours is too.

    I have removed the seal and it says NAK VC 10 16 4 on the back side of it, which is the brand and size of the seal, 10mm ID x 16mm OD x 4mm W.

    I ended up sourcing some double lip seals with metal cases of the correct size from: http://mechaniseals.com/10x16x4tm-t...m-id-x-16-mm-od-x-4-mm-wide-nitrile-material/

    However, they have a $25 minimum order and $7 flat shipping so I just ordered 10 of them. PM me if you need one.
    Disclaimer: I am not a seal expert, so there may be better options out there.

    OGYdIA4l.jpg dAQrtXCl.jpg
    OnJH1Lml.jpg
    Pzbyp5Sl.jpg

    That being said, I have installed the seal the correct way with the addition of some dielectric grease and reassembled the S90. I used a socket with the correct diameter and tapped it into place. It is a tight fit.

    zPJR2QZl.jpg

    To ensure I have the best idle possible, I then coated the back of the throttle plate with dry moly lube to help seal any possible seepage around the throttle plate itself. I also then made a decent gasket from a thick cork/rubber material, since the paper one it comes with is worthless and I didn't want to RTV it on, again, if I didn't have to.

    XTViQ6nl.jpg
    vaSmnTzl.jpg

    I just went and boost leak tested it again and the shaft seal holds fine up to 30psi(highest I can get my little compressor to push out).

    Side note: the throttle plate screws are M4x.7x8mm. They stick out some on the back side and a M4x.7x6mm would probably fit fine.

    Hopefully that helps somebody out there as I was struggling to find information.
     

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  2. gsxtasy

    gsxtasy Proven Member

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    Joined Oct 17, 2002
    Lincoln, Nebraska
    I wanted to update this thread. Apparently the seal on the 74mm s90 is different than the 70mm s90. That being said, these seals that I have referenced only work on the 70mm variant.
     
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  3. amsrn13

    amsrn13 Proven Member

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    danbury, Connecticut
    Ive given up on the s90, I have some seal coming in over seas so i can rebuild it. Im gunna use the oem throttle body as it works perfectly. The people you bought the seals from disappeared with my money, the site is down. Hopefully paypal will get my money back.
     
    My DSM:
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  4. bettfootball

    bettfootball Proven Member

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    Joined Mar 7, 2010
    bettendorf, Iowa
    Bringing up an old thread... What if our TB leaks from the throttle cable side...??? I'm tearing into mine tonight but it seems thats where it is leaking from.
     
  5. GRAVEDIGGER

    GRAVEDIGGER Proven Member

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    Uniontown, Ohio
    There are seals on BOTH sides of the throttle shaft. Just replace them both and you'll be good.
     
    My DSM:
    1991 Eagle Talon TSi AWD

    12.149 @ 115.940 MPH
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  6. bettfootball

    bettfootball Proven Member

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    bettendorf, Iowa
    Oh.. Thank you haha, everything I've read online the last two days says there are no seals on the throttle cable side of an S90. I haven't had the chance to tear it apart yet.
     
  7. ist dwa

    ist dwa Proven Member

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    Centerville, Ohio
    If you can figure out how to seal the cable side let me know, I have tried like 10 different things, all I was able to do was make the leak lesser but no remove it.
     
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  8. bettfootball

    bettfootball Proven Member

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    Will report back.
     
  9. gsxtasy

    gsxtasy Proven Member

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    Lincoln, Nebraska
    For future clarity for people. Just as I mentioned in the original post, there is NOT a seal on the throttle cable side of the 70mm s90.
     
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  10. amsrn13

    amsrn13 Proven Member

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    danbury, Connecticut
    For anyone looking to rebuild a 70mm this is what I purchased. I forgot which one I used but they are very cheap so
     

    Attached Files:

    My DSM:
    1992 Eagle Talon TSi

    Street Build

    645 whp   498 lb/ft
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  11. bettfootball

    bettfootball Proven Member

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    Joined Mar 7, 2010
    bettendorf, Iowa
    Thank you so much!
     
  12. ist dwa

    ist dwa Proven Member

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    Joined Nov 5, 2009
    Centerville, Ohio
    I sealed the cable side of mine over the weekend. It's hard to describe how I did it but it involved making a flat gasket.
     

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