High pitch whistling noise

[Slipstream86]

Hi guys, recently acquired my z4, first time owning one. Looking forward to getting involved with the community

My car is a 3.0i manual 130K miles. It's clearly had some care given by the previous owner but no service book.

Done some searching on here, and can't seem to find another thread with the same symptoms as I'm having.

When the car is warm I'm experiencing a high pitch noise that seems abnormal. It sounds sustained when riding the clutch in 1st or reverse (1st video), or at the bite point changing to second. I'm also hearing something intermittently audible when the car is parked idling in neutral (2nd video).

My ipad mic isn't amazing, so you'll need to turn up your volume to hear is clearly.

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

https://www.youtube.com/watch?v=Ad6A3oRtJkI

To me they sound like the same noise, and seem to be coming from the front of the engine where the belts are. I was concerned it was some part of the clutch assembly at first, but wasn't getting any of the obvious judder or slipping.

Any thoughts or advice appreciated!

Cheers

 

[bigwinn]

Heard before and had mixed success at fixing

If it’s not an idler pulley (aux belt) then it’s an alternator noise

Pop your belt off see if any pulleys are starting to wobble

 

[Mike6]

Could perhaps be slack in the serpentine belt tensioner. Agree above that you need top pop the belt.

 

[Slipstream86]

Thanks guys. I’ve got a 1/2 inch drive torx set with the larger sizes on order for the tensioners, will try to attack it from the top tomorrow by removing the fan shroud to gain access. I’ll probably replace both belts in any case as neither appear to be brand new, and I’ll assess the pulleys.

Is there any reason why the drive belts or associated pulleys would be noisy mostly when the clutch is biting?

 

[Slipstream86]

Started to address this.

I've gone in from the underside in the end. Only reason I planned going at it from the top was that I didn't have a jack! I was waiting for a decent one to come up second hand, but just bit the bullet and bought a new one to get going.

Took off both belts. Main belt seemed in OK condition - a few small cracks. AC belt in worse but not unusable condition. I've replaced the main belt with a new one (thought it was an easy starting point, and obviously its a replaceable component anyway), and re-fitted the existing AC belt.

The tensioners had what seemed like an appropriate amount of force in them. The pulleys all span freely without any grinding, but there is a bit of play in the upper idler pulley, and it has some evident wobble when in motion with the belt.

The noises are now reduced but still present with the new belt, so will replace the suspect idler pulley next.