Noise from belt drive and crackling near the alternator

Today, I took my car to the service center and had them put the front of the vehicle in service mode to investigate an irregular crackling sound that occurs when the engine is running.

I've already been to several workshops, including a Bosch service center, because I suspect the noise is coming from the alternator area.

But, as expected, none of the masters recognized this sound.

I quickly bought a used alternator on eBay, which I'll likely return. When I spin this eBay alternator, it makes a rattling noise, as if there are leaves inside. However, the freewheel pulley works after I managed to get it moving. However, it's still junk because it was operating without a protective cap and is completely rusted.

My free-running pulley seems to be completely broken. I can rotate them in both directions without any difference in power transmission.

Since everything was already disassembled, I immediately tried to check all the bearings.

- Viscous fan for storage, operating silently.
- Silent tensioner.
- The water pump is silent, but noticeably heavier and harder to turn than the rest.
- Hydraulic pump, no noise. A single cracking sound when rotating it quickly back and forth.
- No noises when turning the alternator.

I'm standing there like a complete idiot. When the engine is cold, the V-belt drive makes a noise that is only slightly quieter when the engine is warm, and I don't know why.

Even with new V-belts, it hasn't gotten any better.

And then there's also that irregular, yet persistent, crackling/popping sound.

All abnormal noises coming from the serpentine belt drive disappear when the speed is slightly increased. Then there's just this crackling/popping sound.

Do you have any ideas?

Regards,

Manuel.

And if you give it a little gas, does it become as quiet as a lamb? Or?

Does the A4 with the AFN engine only have a single belt for all auxiliary components? If he has two (like his predecessor), you could remove one to at least somewhat reduce the noise.

Hi Manuel,
Do the noises originate from the stuck freewheel mechanism?

If so, replace it for now (if necessary, even temporarily with the rusty one).
from the iBäh LiMa).

Best regards,
Rudi

Or from a pervert, which is why I asked the question above... The shaft sometimes gets stuck, and then the part swings back and forth miserably, making a lot of noise. If it spins 100 RPM faster, it becomes quiet.

The dealer wants to send me a second alternator. Let's see how the freewheel mechanism is on that one. The cyclist is relatively calm and doesn't appear to be old.

Just wait for the new alternator for now.

I already have a quote for a new INA idler pulley for €75, including VAT.

Regards,

Manuel.

Do you have air conditioning?
A broken compressor coupling could be causing the noise.

Yes, there is climate control, but the noise is definitely coming from the area of the LIMA. On the A4, the air conditioning compressor is located on the opposite side and at the bottom, while the alternator (LIMA) is at the top.

Regards,

Manuel.

Have you had any successes yet?


Best regards, Gunni.

Hey, take a look at the LIMA (likely referring to a specific component or system). If the coals are finished, it's possible they aren't making proper contact, which can cause sparks to jump! And if those sparks are jumping, that's what creates that crackling sound!
I haven't experienced that with my golf clubs before, but I recognize that sound from the alternator in my Civic, and also from my washing machine!

When I looked in the bathroom, which had no light, I noticed that there was always a spark when the washing machine was running, but only in a clockwise direction! If it was running in the other direction, there were no sparks and no noise, only when it sparked.
and the Civic had really bad carbon buildup where sparks were forming!
Okay, check it out! Sure, here's the translation:

'As a tip!'
Best regards, Björn.

First of all, I apologize for taking so long, but the car was still running, etc., etc.

Today, I replaced the LIMA (alternator) including a functional freewheel pulley, and the problem is gone.

Thank you for your help.

It's nice when you no longer have to feel embarrassed at the traffic light because your engine is making a racket like it's running without oil or screws. I'm curious to see if the occasional vibration at idle has now disappeared, as the vibrations at idle are now noticeably lower.

Regards,

Manuel.