Post Title: Update/Need Advice: 2011 SEAT Leon FR 2.0 TDI (170 CEGA) Belt-Side Noise ONLY When Driving (Not at Idle)
Hey everyone,
I’m trying to narrow down a metallic buzzing/chattering noise coming from the belt side of my 2011 SEAT Leon FR 2.0 TDI (170 CEGA).
The weird thing is: it does NOT happen at idle. At idle, the engine sounds completely normal and steady. The noise only kicks in under load or when revving/driving.
Since I don't have tools at home to start stripping it down, I’m taking it to a local garage this Thursday. From researching the VAG 2.0 TDI platform, here is what seems most likely:
Alternator Freewheel Pulley (Overrunning Clutch): When these start seizing up, they often don't make a peep at flat idle, but as soon as RPMs change or you let off the throttle under load, the belt chatters heavily against the tensioner.
Aux Belt Tensioner Assembly: The internal spring/dampener might be worn out, causing the tensioner body to slap under engine load.
A/C Compressor Clutch Bearing: A dry bearing that only rattles when the clutch engages/disengages under load.
Unclipped Intake/Trim: Unlikely to be the alternator itself, but plastic trim or air intake ducting vibrating against the bodywork at specific driving RPMs.
Has anyone dealt with a belt-side chirp/buzz on a 2.0 TDI that only appears off-idle? Did swapping the alternator pulley fix it for you, or was it the tensioner?
Appreciate any insight before I drop it off at the shop!