x5 3.0i knocking noise.
 

SO ever since I purchased this X5 for daily duties at warm idle it has a very faint knocking noise. No codes for anything and doesn't idle rough either. What could it be? Heres a video not of my car but it sounds very much like this. Goes away when revved up.

https://www.youtube.com/watch?v=hybG1Owayys

Could be a rod knock. How many miles or kilometers on the X. What type of oil are you using? Maybe going to a slightly heavier oil will eliminate the noise.

Rod knock is because the clearance between the rod bearing and the engine crankshaft journal has exceeded the design tolerance. The tolerance can be checked with plastigauge but that will require disassembly of the engine.

That's how my e39 sounds and I did a rebuild on the engine. But fail to change the lifters... This could be a possibility

VANOS Seals. Sounds kinda like a diesel. :D

The noise goes away when the engine is revved up though. It has 87,000 miles and has BMW 5w-30 in it.

I know the VANOS can cause that in the V8's, not sure if they make that kind of sound on the I6.

Could also be classic rod knock as already mentioned

VANOS noise in the I6 is more like a rattle.

At higher rpm the oil pump is pushing more fluid and at a higher pressure through the bearings. The additional oil and pressure prevent the rod from knocking. Since the engine doesn't knock at start-up but only knocks once the engine has warmed up, I would try changing the oil to a heavier oil and see if the condition improves.

Hydraulic tappets may knock when the engine first starts up because the oil drains out of the tappet and may require a few moment for the oil pump to fill up the tappets again. They should not be knocking once the engine warms up.

Do a hot oil change and run some good 5w-40 synthetic, its been running quieter for me since I switched to T6 a few years back