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ideola · Joined: 01 Oct 2004 Posts: 15548 Location: Spring Lake MI

As promised, here are the pix:
3mm x 25mm Viton seal:

3/32" x 1" Kalrez seal:

OEM oil feed seal at bracket:

I did not like the fitment of the Kalrez seal. They are only available in standard sizes, and not quite big enough in diameter to compress properly. The Viton 3x25mm seal fits just like OEM.

As for the earlier comment re: the oil feed line seal on the underside of the bracket being square, that is only from long term compression. This is what a new one looks like.
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erstwhile owner of just about every 924 variant ever made

stevekat · Joined: 19 Jan 2008 Posts: 719 Location: Los Angeles, CA

I like the green one! LOL.

It is hard to make out, but if you look carefully, you can see it appears the other seals spell...

T R O U B L E.

(Thanks for the photos.)
_________________
"Never get out of the boat. Absolutely goddamn right. Unless you are goin' all the way."

Gone to new home: '81 924T, US version, CGT Intercooler, UTCIS-PT, Euro DITC, Greddy Trust MBC, Forged Fuchs Flat Dish 6's, Factory Recaro's.

ideola · Joined: 01 Oct 2004 Posts: 15548 Location: Spring Lake MI

Steve, can you please elaborate??? I understand why the Kalrez is trouble, but the Viton seal fits exactly like the OEM seal. Don't understand what you're suggesting...
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erstwhile owner of just about every 924 variant ever made

stevekat · Joined: 19 Jan 2008 Posts: 719 Location: Los Angeles, CA

Partly it is just being facetious, but with the remainder it does appear the green OEM ring is a 'fatty' compared to the viton. It may just be because it is in the other half of the part and appears differently. This o-ring is under very high stress. The heat it experiences is likely extreme, and there have been known failures. If the viton is a 3mm ring, and the OEM 3.15mm, that could be a factor to worry about. I'd also like to know the factory material. Is 400 degrees a high enough value, or too close to the limit? It is a real nightmare to replace - if it were easy than not such a big deal. Might be worth brushing up on your german and finding an appropriate o-ring from a german industrial supply. Or from KKK, or a turbo rebuilder who has a cross-reference. At a minimum, I'd talk to a turbo rebuilder - if they give you the OK, no problem. You may have done that already.
_________________
"Never get out of the boat. Absolutely goddamn right. Unless you are goin' all the way."

Gone to new home: '81 924T, US version, CGT Intercooler, UTCIS-PT, Euro DITC, Greddy Trust MBC, Forged Fuchs Flat Dish 6's, Factory Recaro's.

ideola · Joined: 01 Oct 2004 Posts: 15548 Location: Spring Lake MI

Just to be clear, those are two different applications. The green o-ring is the the TOP seal between the bracket and the housing.

The other one (the one that is now NLA) is the bottom o-ring that goes between the bearing housing and the oil drain line.

I am going to remove the turbo from the freshly built club sport motor and have a look at the OEM version of the bottom seal, and will compare it to the (black) Viton seal pictured above.
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erstwhile owner of just about every 924 variant ever made

stevekat · Joined: 19 Jan 2008 Posts: 719 Location: Los Angeles, CA

Thanks for pointing that out Dan, my bad. Even reading the thread again I became confused! LOL. The one I would have the most concern about is the bracket o-ring where the turbo is mounted and it sounds like that one remains available.
_________________
"Never get out of the boat. Absolutely goddamn right. Unless you are goin' all the way."

Gone to new home: '81 924T, US version, CGT Intercooler, UTCIS-PT, Euro DITC, Greddy Trust MBC, Forged Fuchs Flat Dish 6's, Factory Recaro's.

ideola · Joined: 01 Oct 2004 Posts: 15548 Location: Spring Lake MI

No worries...yes, the top one (the green one) that goes into the bracket is still available at last check.

Planning to compare the 3x25 Viton o-ring from McMaster to the OEM unit later today. Will post pix and observations as soon as I have them.
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erstwhile owner of just about every 924 variant ever made

Min · Posted: Fri Jul 29, 2011 1:53 am Post subject:

What is the part number of the o-rings you purchased? AS568-913? (2.95mm cross section, 25.04mm ID) or AS568-214? (3.53mm cross section, 24.99 ID)

If you give me the dimensions of the o-ring groove that these fit into, we can calculate what size of o-ring needs to be in there to seal correctly.

Min
_________________
Custom means it didn't come from a box.
1980 n/a with EDIS and Megasquirt II Injection. 7 different colors and counting.

ideola · Joined: 01 Oct 2004 Posts: 15548 Location: Spring Lake MI

Click image to go to hi-resolution version on Picasa, and use the magnifying glass / zoom tool to enlarge if desired.

Image 1:
o-ring on left is McMaster-Carr - Item 9263K275, measuring I.D. of 25mm, thickness of 3mm
o-ring in the middle is OEM part 900 174 045 40, measuring I.D. of 25mm, thickness of 3.15mm
o-ring on right is unknown origin & material, measuring I.D. of 25mm, thickness of ~3.6mm

Image 2:
McMaster Carr part in turbo drain attachment piece

Image 3:
OEM part in turbo drain attachment piece

Image 4:
Unknown part in turbo drain attachment piece

The measurement of the recess in the drain attachment piece is I.D. of 25mm, O.D. of ~32.5mm. The outer diameter of the OEM piece uncompressed should equate to 31.3mm.

Also, 3.15mm thickness is .124", so I think we could probably do a .125"x1" o-ring, which will open up many more possibilities of materials.

Thoughts????
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erstwhile owner of just about every 924 variant ever made

ideola · Joined: 01 Oct 2004 Posts: 15548 Location: Spring Lake MI

McMaster-Carr part number 9464K35 looks like a good candidate based on the "actual" dimensions:
Actual thickness = 0.139" (3.5306mm)
Actual I.D. = 0.984" (24.9936mm)
Actual O.D. = 1.262" (32.0548mm)

Also available in an "Viton ETP" compound which purportedly has greater chemical resistance; as well as in a Brown Viton material for easier material identification.

The Kalrez o-ring are stupid expensive @ $86-$89.
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erstwhile owner of just about every 924 variant ever made

stevekat · Joined: 19 Jan 2008 Posts: 719 Location: Los Angeles, CA

Item 9263K275 looks a bit small in cross-section from the photos, but it is shiny in the photo in the part, and the others dull, so optics could be an issue.

I think I'd err slightly larger than slightly smaller, if one had to choose.
_________________
"Never get out of the boat. Absolutely goddamn right. Unless you are goin' all the way."

Gone to new home: '81 924T, US version, CGT Intercooler, UTCIS-PT, Euro DITC, Greddy Trust MBC, Forged Fuchs Flat Dish 6's, Factory Recaro's.

ideola · Joined: 01 Oct 2004 Posts: 15548 Location: Spring Lake MI

I agree. I've ordered a package of the next size up, which should be 3.5mm x 25mm. Both engine installs are delayed anyway, so no big deal to wait another couple of days to get slightly larger seals. Will post more pix when they arrive.
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erstwhile owner of just about every 924 variant ever made

Min · Posted: Fri Jul 29, 2011 5:42 am Post subject:

Ok, I need the depth of the groove these fit into before I can run some calcs.

Min
_________________
Custom means it didn't come from a box.
1980 n/a with EDIS and Megasquirt II Injection. 7 different colors and counting.

ideola · Joined: 01 Oct 2004 Posts: 15548 Location: Spring Lake MI

The groove appears to be ~2.70mm deep. The mating surface on the bearing housing is completely flat, no recess or groove on that side.
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erstwhile owner of just about every 924 variant ever made

Min · Posted: Fri Jul 29, 2011 7:30 am Post subject:

For that gland (groove) depth a o-ring with a cross section of 3.53mm should be used (AS568-214). It will give a 23.5 percent squeeze on the o-ring (which is meant to operate between 20 and 30 percent squish. The listed gland depth for this sealing application (static sealing, internal pressure) is .107 inchs which is 2.72mm

Min
_________________
Custom means it didn't come from a box.
1980 n/a with EDIS and Megasquirt II Injection. 7 different colors and counting.