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S90 Throttle body seal

gsxtasy

Proven Member
859
19
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!

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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.

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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.

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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.

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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.
 

gsxtasy

Proven Member
859
19
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.
 

SasaniFab

Proven Member
2,440
790
Dec 1, 2013
Mexico, 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.
 

bettfootball

10+ Year Contributor
545
549
Mar 7, 2010
Denver, Colorado
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.
 

bettfootball

10+ Year Contributor
545
549
Mar 7, 2010
Denver, Colorado
There are seals on BOTH sides of the throttle shaft. Just replace them both and you'll be good.

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.
 

SasaniFab

Proven Member
2,440
790
Dec 1, 2013
Mexico, 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
 

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bettfootball

10+ Year Contributor
545
549
Mar 7, 2010
Denver, Colorado
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
 
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SasaniFab

Proven Member
2,440
790
Dec 1, 2013
Mexico, Connecticut
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
Im working on it.....waiting to hear back from a bearing manufacturer
 

Mekkentalo

Probationary Member
1
0
Feb 16, 2019
Sweden, Europe
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? :)
 

Remzi

Probationary Member
1
0
Jul 4, 2019
Rotterdam, Europe
@SasaniFab
Any updade about machining on throttel cable side? I got same problem. I saw on youtube, guy doing modify but not good enought (i think).
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