First off, I want to thank the community for all the information that you guys post o

[audiCarMan]

First off, I want to thank the community for all the information that you guys post online. It is very valuable, and as I start dabbling with DIY work on my A4, I will try to contribute as well.


My car started making loud, irregular metallic noises from the front end. When I inspected it, I found that the belt was cracking, so I replaced it (without removing the bumper, thanks to the tips on this forum).

But, the problem didn't go away. I read and listened to many videos that others posted, but still not sure if it is alternator, AC or something else.
Here is a video of the noise, any guess as to what it could be? Another interesting bit is that AC is not cold anymore, although the fan works; also, the noise does not change if I turn AC and Fan on or off.

https://www.youtube.com/watch?v=6nNul2QsRJw

My next step is to take the belt out and run it to make sure its not an issue with timing belt, etc. Thanks in advance.

[JDillon15]

You said it was a metallic noise? Not sure what it sounds like when a bearing is going out (either in the alternator or ac compressor).

[audiCarMan]

You said it was a metallic noise? Not sure what it sounds like when a bearing is going out (either in the alternator or ac compressor).

its certainly metallic, please watch the video if possible. It doesn't sound like clicking noise that some people posted about when the alternator goes out.

[JDillon15]

its certainly metallic, please watch the video if possible. It doesn't sound like clicking noise that some people posted about when the alternator goes out.

I listened to it and wasn't sure. Can you identify where it's coming from?

[RAF_S7]

Could be the belt tensioner...
Does it get worse when you rev or its out on the road?

[Charles.waite]

If you start the car with the Accessory belt removed completely (or just take all the pressure off the tensioner) does the sound persist? If it does, then your sound is likely timing belt or internal engine related. If it goes away then its something on the accessory belt like the PS pump, AC compressor or a bearing or the tensioner itself.

[audiCarMan]

Could be the belt tensioner...
Does it get worse when you rev or its out on the road?

It gets worse if I rev it.

- - - Updated - - -

If you start the car with the Accessory belt removed completely (or just take all the pressure off the tensioner) does the sound persist? If it does, then your sound is likely timing belt or internal engine related. If it goes away then its something on the accessory belt like the PS pump, AC compressor or a bearing or the tensioner itself.

I will try to do that tonight and post the result.

[Gotpsi2008]

Take the belt off again, grab both idler pulled and see is they have any play at all, it sounds like one of the idler bearings let go. Every idler pulley should spin free and almost completely silent.

[audiCarMan]

Take the belt off again, grab both idler pulled and see is they have any play at all, it sounds like one of the idler bearings let go. Every idler pulley should spin free and almost completely silent.

It goes away when I disconnect the belt. I rotated all the pulleys, and there was no significant play in any of them. but, the AC pulley has slight friction and makes a faint noise when I rotate it. Also, worth noting that the front side of it feels like a plate that can move, I am not sure if it is normal or not; see the video of it here:

https://www.youtube.com/watch?v=dtjauXtW3PI

If that is normal, what I am thinking is to get the bumper and radiator off, and them listen to them carefully, should be able to isolate easily that way. Please let me know your thoughts.

[audiCarMan]

An update on this - I got the bumper off and put the radiator in service position to get a better look at the source of the noise. When I put the belt back on, it is what I suspected - AC Compressor. The noise comes when the front plate on the AC pulley pulls in (see video in the last post).

Now to call around check what the labor would be to replace it. Even though it looks easy to replace, I am not sure how to pull the freon out; will see if a mobile shop will do it, driving it with it making such a loud noise is painful.

[Gotpsi2008]

An update on this - I got the bumper off and put the radiator in service position to get a better look at the source of the noise. When I put the belt back on, it is what I suspected - AC Compressor. The noise comes when the front plate on the AC pulley pulls in (see video in the last post).

Now to call around check what the labor would be to replace it. Even though it looks easy to replace, I am not sure how to pull the freon out; will see if a mobile shop will do it, driving it with it making such a loud noise is painful.

You could drain it into the atmosphere and then recharge it later, buuuut I would highly recommend taking it to a shop get the freon drained, doesn't take long at all, then drive it home, replace the AV compressor yourself to save some coin, then bring it back to have them recharge it. I haven't really looked into our compressors very much but I do know some make out there have a replaceable clutch pack and all you need is a puller to get it off(your local autoparts store should carry one). But then again it all depends on what failed, easiest route would be to replace the entire thing

- - - Updated - - -

An update on this - I got the bumper off and put the radiator in service position to get a better look at the source of the noise. When I put the belt back on, it is what I suspected - AC Compressor. The noise comes when the front plate on the AC pulley pulls in (see video in the last post).

Now to call around check what the labor would be to replace it. Even though it looks easy to replace, I am not sure how to pull the freon out; will see if a mobile shop will do it, driving it with it making such a loud noise is painful.

And if you do drive it home without any freon, pull the Ac relay just to be safe

[Charles.waite]

Our AC unit has a swash plate setup so it can properly work with the variable load ac system we have. You can't replace the clutch pack because there isn't one, however I remember seeing someone rebuild their ac unit a while back. They pulled the wheel off and were able to replace a bearing or two on the drive shaft and that solved their problems. You'll likely have to remove the compressor and discharge the system but any ac shop can do that.

I'll see if I can find the link and post it up.