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Old 01-17-2011, 09:37 AM
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bluebee bluebee is offline
Seek to understand,^Value
Location: San Jose, California
Join Date: Mar 2008
Posts: 25,236
Mein Auto: 02 BMW 525i M54 auto 130K
I never understood the DISA (never had to yet) but this is what we have in the bestlinks thread on the problem:
- DISA VALVE FLAP BREAKS: the DISA valve flap breaks, sometimes with parts sucked into the intake manifold (1) (2) (3) (4) (5) (6) (7) (8) & recommended parts (1) (2) & brand selection (1)

The DISA system is named rather confusingly in the E39 glossary as:
- DISA = Differential Air Intake Control (multiple definitions)
- DISA = intake runner length tuning mechanism (multiple definitions)

Googling, I find that a rattling tapping sound from the DISA valve can be easily diagnosed without the need for any special tools:
- BMW E39 E49 M54 Engine DISA valve rebuild

Further googling, I find a new DISA valve goes by a few names & often comes with the o-ring:
- Adjusting Unit with O-Ring for Intake Manifold (DISA Valve) ~$215
- Adjusting Unit for Intake Manifold (DISA Valve) ~$215

And that the o-ring can easily be replaced as a DIY (if you find the o-ring):
- BMW E39 530i DISA valve o-ring replacement

So, as with the lower radiator hose thermoswitch o-ring, the hard part is finding a supplier for that simple o-ring. Thanks Poolman for giving us this link. I'm going to add it to the bestlinks along with the thermoswitch o-ring.

Can someone get us the dimensions of this o-ring when they buy a new one?

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