Hey everyone,
Looking for some ideas on this. This evening I started getting a squealing from the engine bay. It started after a warm start and having driven the car 55 miles since its last oil change. The car has 73,000 miles and is 3500 miles into a new clutch and flywheel.
The weird thing is that the noise goes away when you accelerate and then as the load on the engine decreases, it starts back up. It doesn't see to care about RPM, and a downshift doesn't make it stop. I thought I heard it change pitch when crossing the train track, but it may have been my imagination.
When I got home I popped the engine compartment. The noise was really (really) loud... but it sounds to be coming from under the car rather than the top near the engine cover.


So I shut it down and you can hear the noise slowly stop as the engine stops rotating. When the car is restarted, everything is quiet for a second or two and then starts right back up again.


I am letting it sit to see if it still does it after cooling off.
There are no warning lights on and all the gauges are right at normal levels.


Any ideas? Anything that could be related to the oil change or just bad timing?


Thanks for any help you can provide.
Matt

 

Update:
I pulled the airbox but didn't see anything alarming. Belt appears to be OK, not weathered or cracked. Edges look OK.
The noise sounds to be coming from the underside of the engine.
When revving, a stab of the throttle makes the sound stop. A slow increase to the revs will take the squeal right along with it.


I am inclined to change the belt, as it is the cheap / easy first try.
Appreciate any assistance.

 

air oil separator is the issue...

 

Wow, that was quick. How did you confirm it was the air-oil separator?
BTW, it must have been very satisfying to find the root cause. I'm glad you had it figured out

 

I never realized AOS would make noises. When mine died, I had smoke coming out of the engine bay.

I have a 2007 myself and mine died at around 68k-72k also

 

I've gone through 3 AOS's with my 2002 Boxster and none of them have made any noise.

But I have read reports of other owners who have reported noises that were traced to the AOS. It is not a common symptom of an AOS failure but it is a symptom.

 

When I replaced mine, I did open it up. I bet that if the tears were at the exact locations, I bet the AOS would make noises. Mine had the tears at 7-, 9- and 12 o'clock so I believe the air volume did not create noises. Just WAG.

 

Mine died at around 111,000 miles (2006 C2S) a few track days, and a whole lot of mountain and coastal driving rowing through the gears.

It went out as I exited the freeway and I could have sworn it was some kind of Honda Civic with the big cans on the back and maybe a stuffed Pokémon toy dragging under the rear
bumper.

When I realized it was me, and it was throttle
sensitive, I secretly worried.

Not a very big job and definitely got a good life out of it. Glad you got it figured out quickly.