Cold Start issue - '09 1.8TFSI

[samuelh_888]

Hi All.

Sorry for another cold start post but I'm hoping someone can help. When I start my car, from cold it revs to about 1100 then settles fine. Recently it's been a little bit lumpy but generally ok. I have noticed that if I give a blip on the accelerator there is a choking type noise which sounds like a belt slipping but it's not...

I fitted a RamAir CAI a couple of weeks ago (all hoses and clips are tight) so I'm wondering if this accentuates a noise that already existed. It sounds like it's gulping air but struggling to do so...

The car doesn't have a secondary air pump, could it be a cold idle solenoid, a vacuum leak of some sort, or nothing to worry about?

Hopefully this link to a video works (you can't miss the sound, 10 sec in).

Thanks in advance,
Sam

 

[samuelh_888]

I think I've identified the noise to be the alternator pulley clutch. Sound plausible?

 

[Retroman]

To me listening to a video clip over the internet, it sounds more like an induction sucking noise than a bearing on the auxiliary belt circuit. Old auxiliary belts can harden, crack, stretch and make a screeching noise themselves. If you suspect the auxiliary belt has never been changed, it would be good practice in any event, to change it - they are relatively cheap. When off, you can twist the various pulleys by hand a take a view as to whether they feel rough. They should feel smooth but have a little resistance so than when spun with the palm of you hand they do not continue to spin like a old, rattily roller skate. An alternator clutched pulley is only supposed to spin one way.

 

[samuelh_888]

Thanks @Retroman, I'll get it changed as a process of elimination. The sound 'looks' like it's coming from the alternator. All vacuum pipes are fine and I'd originally through it was the secondary air pump but the car isn't fitted with one. Nevertheless I'll get the belt and pulley changed and see how it goes.
Regards

 

[prt57]

Is it possible to touch the metal case part of the alternator with something like a long screwdriver. Put your ear on the handle end of the screwdriver and get someone to rev the engine to make the noise. You will hear it easily if it is the alternator. Take care as there are moving belts in that area.