The weird thing is, I can sometimes hear it when the X5 is idling. Not very loudly.

But when the engine is off, the noise will come on after a minute. Then it gets louder and more frequent.

Then it goes away in about 5 minutes time.

My plan of action for next week is to take the air box off and find a long screw driver and tap every surface of all the nearby accessory units until I find one where the noises are coming from.

Then replace that part and see if that takes care of it.

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2003 X5 4.6is Estoril Blue, acquired March 2018
2013 128i M Sport 6 MT Space Grey daily driver
2010 535xi 6 MT Barbera Red