Whistling at idle

A6 All/ S6 All
#1

I just started my car after 1 month away, and she was angry. Had to jump the battery, and now I hear a whistling sound around the intake at idle. It goes away under load, but not while revving in neutral. I noticed a mild suction when removing the oil cap, so the engine is under vacuum. No codes, idle is still smooth, just noisy.

I can’t exactly isolate the source, but could this be a torn oil separator diaphragm? I do have a small oil leak somewhere…

here’s a quick video: https://youtu.be/s6u_iPtbpsk

Lets play "Fix it or Scrap it"
#2

You are always going to get suction when you remove the oil cap. That is normal.

That sounds like air getting pulled into the intake past one of the gaskets. Take and just loosen and tighten the bolts around the top Y for the throttle bodies and see if that fixes it

#3

I think I now realize this leak has been around for awhile–but previously I thought it was static from the sound system. I think a month of inactivity may have dried something out causing the volume to increase. But now the whistling comes and goes at different volumes on idle, and definitely disappears when the engine is under load.

I re-tightened the bolts around the top Y, but the throttle bodies seem to require a different bit. 12 point?

#4

Did the tone of the whistling change during the tightening of anything. The throttle bodys I think are a triple square 10.

#5

The tone would change on occasion, but not from tightening. I did touch and wiggle almost everything, nothing I did would cause a consistent change.

But I didn’t have a bit for the throttle body bolts.

#6

You can always try taking a wet rag and put that around the throttle body and see if that helps.

If that’s not it always check the oil separator and the PCV system

#7

After about 100km of driving, the whistling seems to have gone away. Maybe it’s a gasket or seal that has “re-lubricated” after drying out while sitting for a month???

I did find a small tear in the bottom “artery” of the air intake hose near the pass-side TB. But at the time, wiggling the affected hose didn’t seem to affect the whistling. I replaced it with a Latvian special and everything seems fine. Fingers crossed.

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#8

Spoke too soon, still there, but intermittent. I just left it with the mechanic and he’s gonna to a complete inspection.

#9

I found it! or at least my mechanic did.

It was coming from the passenger throttle body/Y-pipe connection near the bottom front bolt. I could put my finger on the spot and it would stop whistling, but also cause a bunch of misfires. I put some hi-temp silicone gasket seal on it for now, and the problem seems to be gone.

However, my mechanic also told me my oil leak is coming from the back of the engine by the firewall. His guess is the camshaft timing chain, but he’d have to take the engine out to be sure. ouch.

#10

“It was coming from the passenger throttle body/Y-pipe connection near the bottom front bolt.” where exactly is this? could you post a picture of this if its not too much trouble. I have seen some whistling like this myself and it seems to go away after a while

#11

My leak was at this spot, but on the underside.

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Intermittent codes - diagnose electrical or mechanical problem?
#12

Thanks for sharing. This turned out to be exactly my problem as well. In my case this turned up on the driver side.

Do you guys think I just need to tighten these bolts per spec and this might go away?

#13

You need a 12-sided hex to tighten those TB bolts. You probably should order a new gasket, PN 078133073J. But in the short term, I used a little silicone RTV gasket paste to plug the leak.