[nomiS330d]

It’s been gradually getting louder for ages now. It’s now time to investigate because it’s becoming annoying.
It’s not a squealing but quite a low pitched hum/whine. It starts getting noisy gradually after about 5 minutes of running. It sounds like it’s coming from the aux belt area. It increases and decreases with engine revs. The clutch peddle position makes no difference.
Anybody have any ideas before I start throwing random parts at it?
I am thinking about getting it warm to start the noise then remove the aux belt and run it for a couple of seconds to see if it’s still there or not. Is this safe?

[MrSweet1991]

Originally Posted by nomiS330d

It’s been gradually getting louder for ages now. It’s now time to investigate because it’s becoming annoying.
It’s not a squealing but quite a low pitched hum/whine. It starts getting noisy gradually after about 5 minutes of running. It sounds like it’s coming from the aux belt area. It increases and decreases with engine revs. The clutch peddle position makes no difference.
Anybody have any ideas before I start throwing random parts at it?
I am thinking about getting it warm to start the noise then remove the aux belt and run it for a couple of seconds to see if it’s still there or not. Is this safe?

Few minutes will be okay mate and probably one of the better ways to diagnose. If it's a failed bearing you should be able to check once you remove the belt and give them a spin like I did with mine.

[nomiS330d]

I removed the belt and started it. Yes the noise went away so decided to change the idler and tensioner pulleys even though they seemed to sound alright when spun. The noise has gone! If it hadn’t it just left the slightly more expensive water pump or the very expensive alternator so happy days.