Engine Bay Squealing Noise Identification

[choppstixxx]

The other day when I started up my Q5, I heard a somewhat loud squealing noise from the front lower left (drivers side) engine area. It only makes the noise when idling, goes away when I rev the engine and also went away completely when I turned on my A/C and defroster (didn't come back after I turned them off either). It sounds like it's coming from the A/C Compressor area, but I am not 100% sure it is the compressor. My car is a 3.0T with about 60k miles, any ideas?

[Aries_27]

The other day when I started up my Q5, I heard a somewhat loud squealing noise from the front lower left (drivers side) engine area. It only makes the noise when idling, goes away when I rev the engine and also went away completely when I turned on my A/C and defroster (didn't come back after I turned them off either). It sounds like it's coming from the A/C Compressor area, but I am not 100% sure it is the compressor. My car is a 3.0T with about 60k miles, any ideas?

I had the same noise this morning. Never had it before and when i went out for lunch it wasn’t there. Same exact thing you’re describing.
I was told it’s possible that it’s the secondary air pump but can’t confirm yet


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[choppstixxx]

I had the same noise this morning. Never had it before and when i went out for lunch it wasn’t there. Same exact thing you’re describing.
I was told it’s possible that it’s the secondary air pump but can’t confirm yet

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I told my buddy that was a Master Audi tech. He had me spray a little brake cleaner on the belt that runs on the A/C compressor to see if it quieted it down, but it didn't change the sound. Then when I pressed my defrost and A/C it went away completely. I will say that I haven't been driving my car as much as usual due to working from home, but it stays in the garage and the only thing I can think of is the recent drop in temps (20-30*).

[Aries_27]

I told my buddy that was a Master Audi tech. He had me spray a little brake cleaner on the belt that runs on the A/C compressor to see if it quieted it down, but it didn't change the sound. Then when I pressed my defrost and A/C it went away completely. I will say that I haven't been driving my car as much as usual due to working from home, but it stays in the garage and the only thing I can think of is the recent drop in temps (20-30*).

Mine stays in the garage every night. I do drive everyday to work. I only get a very light squeal in the morning and at 7-8ish when i leave work. Never during the day. And this morning the noise you had came up and that was it


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[djn876]

Secondary air pump is on the passenger side at least on the 3.0T, could just be the accessory belt that needs to be replaced. Otherwise maybe AC clutch or bearing if it went away when the SC went off. Id start with the belt.

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[GScot]

Sounds can be tricky to pinpoint. I know from experience and got a good tip here on Audizine when I had a squeal that sounded absolutely like a dry ringing bearing. Check your PCV by removing the oil filler cap with the engine running. If the squeal stops that's your clue. The vacuum may be high enough that removing the cap is difficult so just start the engine with the cap off. If all is quiet and the noise starts after replacing the cap it's a strong indicator that the PCV is bad.

If the PCV is bad try to keep miles to a minimum the noise is from the seals squealing as air is drawn in from too much vacuum. There are several write-ups on here to make diy a cinch.

[MSq5]

Secondary air pump is on the passenger side at least on the 3.0T, could just be the accessory belt that needs to be replaced. Otherwise maybe AC clutch or bearing if it went away when the SC went off. Id start with the belt.

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I'm with you. I favor it being either the accessory belt or its tensioner or idler pulley.

I would not want it to break or throw that belt, as it also drives the water pump.

It could be the a/c compressor clutch or bearings, given the report that the squeal stops when its turned off. But, that might be simply due to the load resistance being removed from the accessory belt and tensioner.

On another car I have (non-Audi) the same issue was resolved by replacing the accessory belt tensioner pulley. Its good practice to replace the idler pulley at the same time when you have the belt off. These are cheap parts.

[choppstixxx]

I'm with you. I favor it being either the accessory belt or its tensioner or idler pulley.

I would not want it to break or throw that belt, as it also drives the water pump.

It could be the a/c compressor clutch or bearings, given the report that the squeal stops when its turned off. But, that might be simply due to the load resistance being removed from the accessory belt and tensioner.

On another car I have (non-Audi) the same issue was resolved by replacing the accessory belt tensioner pulley. Its good practice to replace the idler pulley at the same time when you have the belt off. These are cheap parts.

I just ordered a new accessory drive belt from FCP Euro, should be here in a few days. Have a new supercharger belt too that I was going to install anyways for my 60ish thousand mile service. Haven't heard the noise since I turned on/off the A/C, but rather try to sort things out in case it is a bigger issue. Thanks everyone!

[SDV325]

Recently mine started making the same noise as you describing. I'm under 30k miles (45,000 km's)

Did changing the accessory belt fix the issue?

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