Vibration in Auxiliary Belt: Causes & Solutions

Hello.

I know this might have been discussed before, but maybe someone has a tip on how to get rid of these vibrations.
My auxiliary drive belt is vibrating very strongly (amplitude of about 1.5 cm), which can also be heard inside the car. In addition, there is a fluctuation (about 2 Hz), so that the vibration gets louder and quieter. The tensioner seems to still have good pre-tension (nothing is slipping). What can I do about this?
I read in another forum that similar vibrations can also be caused by a loosening timing pulley. However, when I look at it from above, everything seems quiet, and only the pulley of the auxiliary belt might be wobbling slightly, perhaps by about 1mm. The engine starts perfectly, whether cold or warm. However, the multi-tooth screw is still of the old type (there's nothing marked on it).
I'm not really keen on replacing everything just based on suspicion, especially since I just installed the TDI engine (and all its components) into my Golf. Before that, I had an ABS engine in it, and the conversion wasn't something I could finish in a weekend.

Hi from Jan.

Golf III from 1994 with a 1Z engine (125,000 km).

Hello,

Since when has this problem been occurring?
Are the screws connecting the pulley and toothed wheel tight? Are the bearings of the alternator and other components secure?
It's definitely not a known issue. The only way to check is to go under the car and take a look.

Best regards, Rainer.

Thanks for your tips, Rainer. I'm still working on it.
The reservoirs for the headlight, water pump, and power steering pump are all fine. The pulley seems to have some play. I've already bought a new one and will see if that makes a difference.

Hi from Jan.

The tensioner for the ribbed V-belt was loose on my vehicle.

It costs €60 and can be easily replaced if you can loosen the roller (adjust the English setting to 14mm and attach it to the tension arm).

I broke down the details yesterday – pictures and text are in a different thread.
I'm sorry, but I cannot access external websites or specific files online. Therefore, I am unable to translate the text from the provided URL.

Greetings.
Okay, please provide the German text you would like me to translate into English. I will only provide the translation.

Well, the new pulley didn't do anything. The tensioner still has a very good pre-tension. It's probably the vibration damper. Can I replace it without having to remove the entire timing wheel from the crankshaft?

Regards,
January.