Jnameth

Hey everyone

My 2015 3.0l Supercharged Q5 started making a high pitched sound last night, out of the blue. When I was on the accelerator, the sound went away.. but as soon as I let up, the sound came back.

I got it home, and let it sit for a couple hours.. started it up, no sound. Went to bed.. got up, got in to drive to work, no sound for about the first 10 mins of the drive, then it slowly came back. Same issue, same sound.

And not quiet at all.. like I had to turn off the car when stopped at a red light, because it was very noticeable. So, did all my work stuff.. came back out to my car, started if up. No sound. But again, after about 10 mins of driving it came back.

So now I'm home and thought I would fire this trusted forum up, and see what the hell is going on. There is no engine light coming on, and no loss of power when Im driving. If there is a way to post the sound on here as an audio file, I will. Sound is coming from under the hood for by the sounds of it.. near the back of the engine - if I had to guess?


Hopefully someone knows what might be going on. Thanks!


UPLOADED THE SOUND

I just fired it up again to try get more audio, and I guess after sitting for 10 minutes, it stopped.. but undoubtedly will make the sound again next time I go to drive it. Also added the normal engine sound, without the mystery sound.

Bob Petruska

I would lean towards a bad PCV valve, It is under the supercharger and costly to replace at a dealer.


I could also be something else…

Jnameth

Thank you for the reply!

This sound does sound very similar to the sound I am getting for sure. Next time I drive it, and the sound fires back up, I will pull the oil cap and see if the sound goes away. Pretty easy diagnosis if the sound does vanish - according to the video.

Question is, am I doing irreparable damage by driving it at all? Like I say, the sound doesnt come up until the car has been driven for about 10 minutes.

Bob Petruska

That's a good question and I really don't know. Maybe other readers will respond on this. Are you consuming more oil than normally?

If the defective PCV increases the internal engine pressure substantially you "could" cause rear main bearing seal rupture (major rear seal oil leak) and would need to pull the engine to repair.

If I remember correctly the cost to replace the PCV on that engine was approximately $1500 - 2000, it really sucks that you need to remove the supercharger to replace a part that costs about $150.

Jnameth

Oil consumption might be on the higher-side of normal, but nothing wild. No smoke or anything coming from engine or exhaust.

and you're right.. having to take the SC off for almost any kind of repair in this area, is pretty gross. Makes me wonder what else I should get done as preventative maintenance while the SC is off. Any suggestions - by you, or anyone else reading this?

I have about 145,000km on it right now.. or about 90,000 Miles. I replaced the water pump last year, and other than that, the car is in great shape. Love the car, and super happy with still, and hopefully for years to come.

stash64

Not sure about the 3.0, but with the 2.0T it can quickly lead to a blown rear main seal due to excessive crankcase pressure and apparently a weak seal design.

stash64

Here is at least one advantage/plus for the 2.0T. I changed my own PCV valve recently in less than half an hour and using the OE part for under $100. Not really any more difficult than an oil change.

stash64

If you do have the PCV serviced, you might want to have the 2 heat exchangers inside the supercharger replaced at the same time. I came across a video somewhere and apparently the heat exchangers get crudded up and become less effective over time.

Jnameth

Update: So when I have been driving for a bit, and it starts to make the high pitched sound - I pulled over, I pull the oil cap, and start the car, the sound is gone.. and there is a huge amount of suction from the open oil cap hole.. so much so, that when I put the cap close, it sucks it right in.

Bob Petruska

So you answered your own question. Time for PCV replacement.