What are faulty DISA symptoms on an N52?

[Tango22]

Hi all, I've noticed over the last week or so a randomly appearing rattling noise from my E85 2.5. It's a 2006 with the N52 engine and has covered 161k miles.

It appears randomly and only for a few seconds at a time then vanishes. Sometimes it won't do it again for a few hours then will come back for a few seconds and do it again. For example it didn't do it from cold yesterday morning when I went out in it but when I got home and pulled slowly into the driveway I heard it for a few seconds then it stopped. Then 15 mins later when I slowly drove it into the garage it did it briefly again.

Is this a possible DISA valve issue do you think? It's hard to describe the noise but it does sound quite 'plasticky' rather than metallic if that makes sense?

It's intermittent so difficult to get a sound clip of, but unlike some videos with dodgy DISA valves I've seen, this sound isn't there all the time.

[Zedebee]

It is not difficult to pull out the DISA for cleaning/inspection if you are worried about it.

Have you had a good listen under the bonnet to identify where the rattle is coming from? DISA is inboard of the rectangular box mounted to the inlet manifold. A rattly culprit in this area could also be the ICV which is mounted immediately below the DISA (in an M54, I assume the same for N52).

[Tango22]

The problem with trying to listen for it is that it makes the noise totally randomly- I could pop the bonnet, sit with it idling for 5 mins and it wouldn't make the noise. Then I go to move it forward and it makes the rattle for a few seconds then stops!

I'll check the DISA valve and take it out to see if it looks worn. Am I right in thinking there are two DISA's? One easy to get to and one an utter pain to access?

[Tango22]

Actually, from searching on Google it looks like the N52 2.5 'non-Si' with 177bhp only has one DISA valve as it doesn't have the three stage manifold the 2.5 Si has.

That right?

[Zedebee]

That sounds right. It’s the outer one (which I believe is common to all M54/N52) which can have the problem with the valve disintegrating in any case.

[smorris_12]

That's interesting. I thought only the 3.0Si got the three stages manifold.

[Tango22]

Okay, folks.....can someone point me in the right direction for a decent quality replacement I can order up?

Ta.