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Thread: DISA 0 Ring
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Old 03-17-2011, 11:46 AM
rdl rdl is offline
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Location: Ontario, Canada
Join Date: Jun 2010
Posts: 1,790
Mein Auto: 530i 2003
I've got a small vacuum leak in my DISA to inlet manifold joint. So I measured my DISA today hoping I'll be able to buy a replacement at a local industrial supply house.
The car is a build date 9/2002 M54 3 litre with 126,000 km. The DISA doesn't appear to have been serviced but I don't know for a fact.

I tried to lift the DISA's red rubber sealing ring but it adhered to the the groove in the sleeve. I managed to lift sections of it from the groove without tearing/breaking it. The sealing ring appeared to be rectangular in cross section. There were no signs of being a deformed, compressed round shape. FWIW, pictures of new M54 DISA units appear to me to have a flat sealing surface consistent with a rectangular shape too. But, this is really a guess from pictures with not quite enough resolution. The sealing ring surface was flat as seen with a jeweller's loupe, to the limits of my vision. No sign of a bulge upwards as the remnants of an originally round O-ring.

Dimensions I got with digital vernier calipers were:
1 ID of receiving bore in manifold 61.5 mm
2 OD of DISA insertion sleeve 61.3 mm
3 width of groove in DISA sleeve 3.25 mm
4 depth of groove in DISA sleeve 1.7 - 1.8 mm, say 1.75 mm
Calculated values:
1 clearance from DISA sleeve to manifold = 0.1 mm
2 bottom of groove to manifold bore = 1.85 mm
FYI 1 mm = 0.040 (actually 0.03937) inches for those of you wishing to convert to more familiar units.

I'm going to hunt for any of the following:
1 57 mm ID x 2.5 mm dia round O-ring
2 58 mm ID x 2 mm dia round O-ring
3 58 mm ID x 2 mm x 3 mm rectangular seal ring
4 57 mm ID x 2.5 mm x 3 mm rectangular seal ring
I don't plan being choosy on material. Nitrile seals are commonly available and should be suitable for the application. There is minimal exposure to gasoline, oil or even heat.
Then we'll see if I'm brave enough to remove (& almost certainly ruin) the current, sort of OK seal.
If I have any luck I'll report back on results.

If anyone else wants to try the same trial, please be good enough to report your results.


Last edited by rdl; 03-17-2011 at 11:48 AM. Reason: correct potential sizes
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