If it is a rhythmic clicking or knocking, it could well be some of the actuators that open/close the vents for the HVAC.
I don't know about the Mk4, but on the Mk5 there are several and they are a fairly expensive part for what is just a 12/13V DC motor and a potentiometer
If you can hook your card up to VCDS it might guide you to which ones are causing the problem.
You'll find guides online for how to wash the pots (helped for about a day or so for me), replace the pots (again, only a temporary fix for me) or replace the motors themselves (AliExpress or Ebay).
This is one of the actuators from the MkV
Thanks for the info brother!! Yea it happened again but seems to disappear as long as I have the air in Auto mode and don't go below 22c.. Soon as I lower the temp down that noise comes back. If turn auto air off and turn the fans completely off, the noise is still present. If I leave it in Auto mode and turn everything off the noise is gone.. like the other modes are engaging something but auto mode doesn't?.. Super weird.. I guess I'll have to dive deeper with a VW mechanic or something.. I hate cabin noises lol.
I had one more weird thing happen yesterday and today. After a cold start I heard a similar style knocking noise coming from the rear end just not as loud. Both times it occurred after I moved the car like 20 feet about to pull out into traffic. So I went from a cold start in my parking spot to first gear then a complete stop before pulling out into traffic, sitting in neutral. Then a faint knocking noise over and over in the rear end for like 5/10 seconds.
After driving for 5 minutes and stopping again to listen, there's nothing and even after an hour still nothing. I am wondering if its the differential or something? It's only happened twice now but I have zero clue. So hard to figure odd sounds unless something is actually malfunction or broken. I'm new to the car and don't know if its a normal thing. Maybe the diff or Haldex system warming up or something or just on its on its way out.. She only has 87k miles so nothing crazy and the maintenance records looks good. I'm still researching common issues and haven't had the car long enough.
Edited by exodus1337, 18 April 2021 - 07:52 PM.