[2.0 TDI 140 CFFB] Humming noise - video inside

[balzout]

Hi,

just bought a 2011 A3 8P cabriolet/convertible 2.0 TDI 140 (CFFB) with an annoying humming noise. I've had enough 2.0 TDI 140 in the past (A3 SB 2009, Passat B6 and 2x Passat B7) to distinguish this abnormal noise. It disappears as soon as I turn right, even just slightly.

I've searched through the web & youtube and the most obvious diagnostic would be a dead wheel bearing, but the noise also disappears when I press the clutch. In this perspective, as the wheel still runs at the same rotation speed the noise should remain the same no ?


Short video (3 footages) here to share the problem, thanks for your help !
 

 

[cliffcoggin]

Hello Balzout.

I doubt that it is a worn wheel bearing, the sound is wrong and would be unaffected by clutch operation. However a wheel bearing can be tested by jacking it off the ground and turning the wheel by hand. A worn bearing will make a low rumbling sound. You may even be able to feel looseness in the bearing if you rock the wheel left/right and top/bottom. Don't be misled by any scraping or scuffing sound from the brake discs.

I speculate that there might be vibration of the clutch hydraulic pipe against some part of the steering linkage. That would explain why the noise is affected by turning and clutch operation. My car is an automatic so I don't know the route of the pipe, hence my idea could be sheer nonsense. Nevertheless it would be worth looking at the pipe route around the engine bay, rattling it in search of loose clips. Check too that the steering rack is firmly mounted by getting another person to move the steering wheel to and fro while you look at the rack.

[balzout]

Thanks for these great tips 👍