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S90 Throttle body seal

Posted by gsxtasy, Mar 22, 2016

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  1. gsxtasy

    gsxtasy Proven Member

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    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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    1995 Mitsubishi Eclipse GSX
    manual · 2G DSM
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  2. gsxtasy

    gsxtasy Proven Member

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    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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    1995 Mitsubishi Eclipse GSX
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  3. amsrn13

    amsrn13 Freelancer

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    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.
     

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  4. bettfootball

    bettfootball Proven Member

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    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.
     

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    1999 Mitsubishi Eclipse GSX
    awd · manual · 2G DSM
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  5. GRAVEDIGGER

    GRAVEDIGGER Proven Member

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    There are seals on BOTH sides of the throttle shaft. Just replace them both and you'll be good.
     

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  6. bettfootball

    bettfootball Proven Member

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    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.
     

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  7. ist dwa

    ist dwa Proven Member

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    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.
     

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    1999 Mitsubishi Eclipse GSX
    awd · manual · 2G DSM
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  9. gsxtasy

    gsxtasy Proven Member

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    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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    1995 Mitsubishi Eclipse GSX
    manual · 2G DSM
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  10. amsrn13

    amsrn13 Freelancer

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    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:

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    1992 Eagle Talon TSi
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  11. bettfootball

    bettfootball Proven Member

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    Thank you so much!
     

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    1999 Mitsubishi Eclipse GSX
    awd · manual · 2G DSM
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  12. ist dwa

    ist dwa Proven Member

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    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.
     
  13. bettfootball

    bettfootball Proven Member

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    Alright, I'm so tired of the s90... I flipped the stock seal and it still leaks insanely bad. I'm going to source a higher quality seal for my 74mm S90. (which upon review is the same marking as the 70mm, NAK VC 10 16 4) But I'm stumped as to what to do on the throttle cable side??

    How can I seal this up since there is no provision for a seal? Any ideas? I can't stand the whistling from the s90. Driving me insane..

    -Brady
     
    Last edited: Jan 2, 2019

    Street Build 290  1

    1999 Mitsubishi Eclipse GSX
    awd · manual · 2G DSM
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  14. amsrn13

    amsrn13 Freelancer

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    Im working on it.....waiting to hear back from a bearing manufacturer
     

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    1992 Eagle Talon TSi
    645 whp · 498 lb/ft · 1G DSM
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  15. amsrn13

    amsrn13 Freelancer

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    The throttle body is going to the machine shop friday, nobody seems to have the dimensions i require to work around getting a seal on the tps side. Ill keep everyone updated
     

    Street Build 3K  20

    1992 Eagle Talon TSi
    645 whp · 498 lb/ft · 1G DSM
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  16. bettfootball

    bettfootball Proven Member

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    Could you explain a little more?
     

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    1999 Mitsubishi Eclipse GSX
    awd · manual · 2G DSM
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  17. Mekkentalo

    Mekkentalo Probationary Member

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    Any updates on this? About to order a 74mm for my build? Anyone got a link for the steel caged seals that fit?
    @amsrn13 wanna share your sealmod for tps side? :)
     
  18. amsrn13

    amsrn13 Freelancer

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    I am machining oring grooves in bearings that I will be selling shortly. machining bearings is a pain in the ass
     

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    1992 Eagle Talon TSi
    645 whp · 498 lb/ft · 1G DSM
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