Hello everyone,
Fabia 2016, 1.2 tsi, manual gear
for the last few weeks I have a strange (belt like-I recorded the sound, in the file bellow) noise that seems to happend in a sicquence like that:
1. after at least 10 min driving (maybe when things stars to warm-up)
2. after I Pass 80 km/h, then when I decealerate (barke or just release the gas paddle)
3. when the car speed is between 50-20 km/h
4. I thought it was the alternator belt cause the sound seems the same- after change it to a new one nothing changes.

any ideas where it comes from?

thanks

Maybe your best plan would be to remove the auxiliary belt while the engine is warm up or hot and then see if that noise has disappeared, if so then it has to be one of the driven components.

 

Or before doing that, while it is making that noise, switch on the headlights and rear screen heater - if it now makes more noise then it will just be alternator bearings. 

 

Something else to try is, switch AC completely off, ie switch to ECO mode, is that noise still happened, if it is then switch on the AC and demand cooling, is the noise changing at all to indicate that it could be the AC compressor.

 

After that there are a few rollers and belt tensioner to consider, but you could check them sort of, while you had the auxiliary belt off and the engine stopped.

 

One other outside possibility is the EVAP valve being activated, but I don't think that that happens during idling, unplugging the EVAP power lead would be one way to check if it was that, though normally that makes a beeep beep beeping noise when the engine has warmed up and the engine speed is above idle speed.

 

Finally, does the auto stop/start still operate, if not then check the voltage across the battery at idle and at increased engine revs.

 

Edit:- that final comment concerning the battery voltage, should have included that if your battery is dying, then even at idle the alternator will still be trying to charge it back up and so putting a heavy load demand on the alternator and its belt etc - so while that might point to alternator bearings, it could also be getting made worse because the battery is in poor health.

Edited 2 February, 20224 yr by rum4mo

I was just typing, but rum4mo has given much more instructional information to my guesses.

 

Personally I am not adverse to spraying a good liquid lubricant like GT85 on one SUITABLE item at a time to see if that alters the sound.  I have known it to take away the sound (and even not to return) but that was only luck, perhaps washing away grit/grime/crud and/or lubricating.

 

My guesses were. -

 

Alternator?  A pulley?  Compressor?

 

Edited 2 February, 20224 yr by nta16

100% the one way sprag clutch on the alternator pulley and that is after listening for only 3 seconds!

 

Unless of course the Fabia does not have one in which case I will get my coat!

 

Nearly all of my mistaken assumptions end up being in regard to the Fabia, Wino always patiently and politely corrects me.

Edited 2 February, 20224 yr by J.R.

Thank you everyone!
I will work on it and will come back soon with updates