Can probably be one of many things...

B6/7 S4/RS4
#1

Can probably be one of many things but I thought I’d ask.

I just started getting this high pitched whiny noise that sounds somewhat like a belt whine when the car is cold and running above 2k rpms.

Once the car is hot, the noise goes away but when it’s still cold and I accelerate, the noise is there, when I decelerate, the noise is there but if I decelerate and let the revs drop below 2k rpms, the sound goes away (or, if I’m above 2k rpms but put the clutch in, once the revs drop below 2k rpms, the noise goes away).

Any thoughts?

#2

sounds like what happens when the stock serp belt tensioners begin to fail… I cant recall if thats replaced in the blower kit though

#3

I would try to first narrow it down some by having someone rev the car with the hood open to the range that you are talking about (obviously out of gear, parking brake on), and see if you can make a partial diagnosis that way, or at least eliminate some things.

Bearings can make a whine-like sound when they are going bad. Usually pretty high pitched, which can vary with rotational speed.

#4

Engine speed or forward velocity speed?

#5

Sorry, I was just speaking generally. Meaning, when a bearing is rotating at a higher speed. I was not referencing any specific bearing on the vehicle. Apologies for the confusion.

#6

Another thought, since you said when things warm up it goes away… what about a small air leak? As things heat up, they seal better cause of the expansion.

Also, since it is RPM dependent, pressures/flow rates are going to be higher at higher RPM’s so you would be more likely to hear a leak as you accelerate etc.

#7

100% a possibility, I had a small vac leak on my s4 from gasket matching the intake ports and it had this exact behavior

#8

I also had the same vac leak coming from the IM on my S4. I removed the intake and replaced the gasket and the whine went away for a few weeks then came back. The next time I just loosened all the IM bolts and kind of picked it up and re-seated it down and torqued all the bolts again. The noise hasn’t come back since and it’s been months.

I nailed down where my noise was coming from and tightening the torx screws near the sound would change the pitch. If your noise sounds like it’s around the IM you could try that.

#9

I would follow the manifold bolts loosen then tighten in the star pattern idea expressed above by the sniper.

#10

I would also use a torque wrench and verify what the torque should be (sorry, I don’t know the specs myself). Nothing worse than having to extract a broken bolt from your lower intake/block.

#11

11 Nm is the torque spec and I end up checking each bolt like four times to make sure. The pattern
Audi shows starts in the middle then works its way to the far corners too.