2011 N55 rattle when revs dropping

[mr2turbogts]

I have a 2011 335i with the N55 engine, and there is a rattle/nasty bearing sound coming from just below the alternator.

The sound is only there we you lift the accelerator, I.e as the engine drops the revs.

I thought it was a watergate rattle but think it’s in the wrong place, what else could it potentially be?

Strange it only happens off load

[GreenV8S]

Perhaps a bearing or clutch on one of the belt driven ancillaries.

A mechanic's stethoscope is a good way to track this sort of thing down.

[mr2turbogts]

Thanks for the reply, that’s what I initially thought.

Especially as it comes on off load

[E-bmw]

GreenV8S said:

Perhaps a bearing or clutch on one of the belt driven ancillaries.

A mechanic's stethoscope is a good way to track this sort of thing down.

^^^^ Wot 'e said.

As the tension drops the belt will slow & cause something in the belt path to rattle, alternator/idler/A/C pulley etc, one will be the cause.

[mr2turbogts]

I think you guys are right, the more I read up on it. Would say its the A/C pully too.

Got it going into a garage tonight, fingers crossed