Audi A4 AFN Belt Noise: Common Causes & Fixes

Hello community!

I have the following problem.

On my 1998 A4 Avant with the AFN engine, I always hear a noise from the belt drive during cold starts in the morning when it's very cold outside, i.e., below freezing temperatures.
The noise sounds more metallic than squeaky. It only occurs when the engine is idling; as soon as I give it a little gas while stationary, it disappears. Furthermore, it goes away after driving for a few kilometers.
I've now replaced the clutch on the Lima generator, but it didn't solve the problem.

Somewhere on the internet, I once saw a video that had the same symptoms as mine, where the crankshaft pulley was defective. Do you think it could be that?
Or the belt tensioner?

Thank you for your help!

Best regards.
Bernd.

Quote:

Somewhere on the internet, I once saw a video that had the same symptoms as mine, where the crankshaft pulley was defective. Do you think it could be that? Or the belt tensioner?

The belt tensioner is often a reliable component. However, before you start replacing everything,
Make sure that the noise is actually caused by the belt drive and not the timing belt.

If the crankshaft pulley is affected, the lower timing belt pulley should wobble or move sideways.

OK, thank you!

I'm just going to remove the V-belts and try starting it. If the noise disappears, then I know it's coming from the V-belts.


I would have also suspected the belt tensioner. When I reinstalled the serpentine belt recently, I manually turned the tensioner pulley, and it made a rather loud noise.

I already checked the pulley; it's running perfectly smoothly and isn't wobbling.
If the rubber on the pulley were damaged, it would wobble and that would cause the noise.
But because the noise is metallic, like a faulty bearing, I would probably be best off using a wrench.

Could it be that the cold weather is causing excessive play in the wrench's bearing, which is then producing the noise?

It could also be the power steering pump, water pump, or air conditioning compressor, of course!

Sure, here is the translation of the text from German to English:

"Best regards," or "Sincerely,"

Quote:

Could it be that the cold weather causes excessive play in the wrench's bearing, which then creates the noise?

Yes, if the engine is mounted transversely.
In the next post, please provide some details about the vehicle .

The car is a 1998 Audi A4 Avant with a 110 horsepower TDI engine (AFN), which is a longitudinally mounted engine, and it has approximately 300,000 kilometers on the odometer.

Silly question now, but does it not matter to the mechanic whether the engine is mounted longitudinally or transversely?


Sure, here is the translation of the text from German to English:

"lg" translates to "best regards" or "kindly regards" in English. It is a common abbreviation used at the end of emails and letters.

Quote:

That's a silly question now, but doesn't it not matter to the spanner whether the engine is mounted longitudinally or transversely?

No, a different system is installed when doing a cross-installation.
A long, angled lever passes through the pump bracket. The tensioner pulley is located on the angled side, while the actual tensioning element is at the other end. These components can also make a metallic rattling noise when they are worn out.

When working on an A4, if there is a suspicion of tension in a component, I sometimes go ahead and insert a long, flat screwdriver between the fixed and moving parts of the tensioner while the engine is running, to more or less block it. When under tension, the noise disappears. BUT BE CAREFUL This is not for people with large motor skills --> risk of accidents.
If the tensioner roller appears to be misaligned or tilted, you can directly replace the tensioner.

Okay, thanks, I'll give it a try.

Before I noticed something else in the garage: when I loosen the serpentine belt, the tensioner pulley makes a "creaking" noise and only moves jerkily or in steps, not "smoothly."

I would also like to say that this shouldn't be the case.


Best regards.
Bernd.

Quote:

I would now also like to say that it shouldn't be like that.

"That's how it is --> so, replace it. However, it's not necessarily responsible for the noise..."

I would recommend replacing the tensioner. It was also the case with my AFN engine in an A4 with 350,000 km. However, at a low RPM, the belt suddenly broke .

The problem was that the tensioner pulley had been replaced individually without replacing the bracket. The noise disappeared initially, but then returned. The alternator clutch (freewheel) was okay. The pulley itself showed no visible imbalance.

After the breakdown, I completely replaced the entire tensioner assembly and also the pulley, because it's really frustrating to break down due to such a small thing .

Furthermore, the serpentine belt was difficult to deal with; I even had to remove the timing belt in order to get rid of all the debris.