Basically sounds like this: I've got both belts, and everything that goes with it replaced with an aftermarket parts (INA). It only does that on cold start, and not every time. I've tried previously spraying both belts inside and outside with WD40 which didn't help at first, but after the noise was gone for a whole month. Where should I start my investigation? Try spraying WD-40 on pulleys bearings and see if the noise is going away?