Screeching Engine Whistle/Squeal/Whine

Hi All... HELP. Had been all over this forum (and one or two others) of late trying to track down my own teapot-sounding whistle, and I initially figured I wouldn't litter the board with another thread having posted on the last whistle thread... but here I am as many folks seemed to have moved on a bit (but thanks eharrison!). I have a sneaky suspicion this is an AOS issue, but hold out hope it is not. I would greatly it if appreciate others who haven't checked back there in a while could examine this one. The sound doesn't fit any previously posted, thus this thread... the somewhat dizzying (sorry) vid covers it at its worst, as I hovered across the rear. Sound is loudest near left/center (it seems) of the engine, but it's hard to tell when it's blasting in your ear. At the very end of the vid, right after I shut the engine off, you'll hear the noise rise to a very high-pitched crescendo then suddenly stop. Odd. It�s a 1999 996 C2 Cab with about 103k, and not been serviced since 75k (don't ask). Oil level was very low of late, but back to normal with a quart and a half topped. Clutch (and TOB) replaced 20k ago. No issues shifting, tranny seems normal (no issues), idle OK. Tran fluid, however, is a wee bit overdue for a change (understatement, yes). No fluid leaks anywhere I can see. From cold, the noise is faint if nonexistent for about 10 minutes of driving, then frequently off and on once the engine temp hits about 200 (??-- roughly between the 8 and the 0 of the 180 on the guage-- could never read that right, but normal I'd say). Oil pressure hangs around 4-5 for that time, then settles in after regular driving (20-70 mph on my commute home) at around 2-3 if not a bit lower, and now drops to the floor at idle. Once the noise starts kicking in every 20 seconds or so, the oil warning light pops on and off... can make both the noise and the light cut out with a punch on the gas, but it's temporary. Damn thing is LOUD at times. Started a few days ago. I did pull the oil filler cap off and felt a bit of vacuum-y suction... definitely something noticeable. Engine started to sputter quite a bit and nearly cut out after a few seconds until I quickly recapped it. Checked tension on, then later removed, the serpentine belt... sound still there. Sooo... am I in for an AOS job? (Rough cost?) Is a tranny fluid swap worth it first (per the other thread)? Should I not park this near small children? http://www.youtube.com/watch?v=T-HRgzinLEo HELP.

1st off wash that car! second - open the engine bay 3rd.. thats a crack up when you shut it off! I would suggest removing the belt and running it - (quickly isolates that) - sounds like a cracked hose somewhere The AOS is not a big deal, if it is that... just change it. If not while going after it look for broken lines. but for sure open the engine and see if you can find the noise with your finger cheers and good luck

Whoa! thats a hell of a noise. I have no idea what wrong..sorry! But since you are local you should try and make one of the Cars and Croissant meets in Chathem. Cars & Croissants link

Keep people a safe distance from your car if you start it. 28K miles without servicing? Intermitenent oil light with a squeal like that is not good. If this is a serious post, I'd recommend not running the motor for fear of locking it up. Sounds like a bearing that is about to seize. IMS maybe? Hope I'm wrong.

You may want to consult with a Porsche mechanic if removing your belt as suggested didn't eliminate that noise. GL

not a bearing - listen to the very end of the vid - at first I was going to say pulley bearing... but the last second of the vid says vacuum hose FOR SURE

Low oil pressure to the point the light's coming on and the noise... I don't like it. Absent the low oil pressure warning light I'd take WAG and say AOS. You eliminated anything related to the serpentine belt and accessory drives. That the noise changes when you shut off the engine suggests it is engine vacuum related and this points to AOS. A bit of vacuum at the oil filler tube is normal. The engine reacted as expected. In my experience at least one AOS failure the vacuum was so great at idle I could not remove the oil filler tube cap against the pressure difference. The low oil pressure and the noise could be unrelated. But the low oil pressure warning light troubling. My advice would be to get the car to a qualified tech and have the low oil pressure checked out. Could be a bad sender or something other than actual low oil pressure. Generally these engines have a robust oil pump and oil delivery system but there are exceptions. With that kind of noise if it was the AOS putting one's hand on it should feel the vibration the noise is causing. However, you want to be very careful sticking your hand anywhere around a running engine. Get a hand or sleeve caught in the serpentine belt and your scream will drown out the squeal from the engine. A tech would put the car on the lift and give a good listen from under the car walking around and listening from various points and thus narrowing the source of the noise down. I've seen a tech break out a stethescope to more precisely pinpoint the source of an engine noise. But I'd also seek to verify the oil pressure is good before running the engine too much. If the oil pressure is good and the problem's just a sender or perhaps something else, other than actual too low oil pressure, that's one thing. If the oil pressure is low, truely low, then the noise and and the low oil pressure might be related. Could be a bypass valve partially stuck open or even an internal oil leak that is causing the noise and the low oil pressure. Without too much effort the AOS could be eliminated. As I said, it is causing that noise feeling the thing should clue you in it is the source of the noise. But I'd verify the oil pressure ok first. Sincerely, Macster.

It is possible the oil (I am sorry I missed that in the OP) issue is un-related... but I would NOT be comfortable with ANY oil light issue my 0.02 change AOS and oil pressure sending unit - then see if its gone. If you can do the work its under $200 for both, if not... maybe $700-1000 (guess)

Thanks very much, all. I opened the engine and couldn't locate it... to be honest I've not wanted to leave it running long enough again to get it squealing, and when it's going it's hard to pinpoint given the noise seems to come from everywhere. The oil light only comes on when the pressure drops to near/at zero, usually at idle or at very low speed/rpm, but disappears with any acceleration. The vacuum at the cap isn't that strong (I'd put it at a strong dustbuster, not a Dyson).. the only reason why I think the oil is related is due to both issues occurring near-simultaneously... doesn't have to be, I know, but mildly suspicious. Haven't been able to get it to a tech as yet since I'm waiting on my next foray to Germany to leave it... not for two weeks though, thus why I'm trying to get this sorted beforehand. (Marc - Thanks for the invite... will try and attend one of those... may take the car to Gene at Autohaus anyway, if he has the room.)

what oil are you running when was it last changed - you added 1.5qts...? those could all cause that - these two things might be independant...sounds like you are behind the basic maintenance curve a bit?? start there too - and as stated, swap the parts in post #8

M1 0W40... last changed at about 7k ago. Topped off with a bit of M1 10W30 as it was still a wee bit short, but I doubt the mix would have any effect (the whine started well before). To say I'm behind the basic maintenance curve is a mild understatement, though I've had the plugs and coils replaced at 7k as well, filters are new, etc.

what are the temps in your area lately? I would suggest a differant oil with the change (but dont want to start that again)

Temps are back to normal. Using the 0 has never been an issue in the past, however.

wow, you cant even pass that one off to your passenger as "Oh thats the turbo" Man that is the 2nd most annoying sound I have ever heard

Sounds like a dying air oil separator - my 986 had a similar 'whale falling from 40,000' soundtrack... Trip to the stealership required - or some knuckle bashing DIY

I heard that whining sound from another thread and most of the guys posted there that it might be the secondary air pump.

could be the idle belt tensioner bearing

it is the AOS, remove the oil cap and the noise should go away, alto the car will run rough This one was of the first issues i had with my car. the AOS was defective it was putting way too much vacuum on the crank case causing air to sequel past the seals making god awful noises. the increased vacuum causes the oil pressure to read loader causing it to flicker on and off at idle least this is what happened to my car.... replace AOS and everything went back to normal

Either that or a check valve is stuck partially open or clogged a bit, or some secondary air hose has cracked. I tend to think it's the AOS. It's in today for another check... had someone under it with a stethoscope and it's not coming from the engine itself, which is a good thing. We shall see.

AOS..Especially if it only does it at and just above idle Its killing the oil pressure and volume to the bearings as well.

Don't ask me why I remembered NOW to follow up on this thread, but for those who endured the pain of the vid and responded, I figure I owe at least the courtesy of a verdict, albeit late... it was a biblical failure of the AOS. Other than the several hundred to fix, it was almost worth it to view the stunned/bemused/horrified looks of those who had the pleasure of hearing this first hand. And now off to swap out DME relays and fuel pump fuses in the hope that'll fix my latest issue of the engine cutting out. Old oil sludge ain't helping either. Sigh. Thanks again all.

I have a similar noise on my 2000 996. When I pull the dipstick out, the sound goes away. The sound also goes away when I open the oil filler cap. I think it is a vacuum issue - right?? Also, after messing around open the oil filler cap yesterday, I started the car today and there was a lot of smoke - whitish, grayish. Yikes - but I'm hoping this is some kind of blow back. OR - does anyone think this is leading to an AOS swap? Thanks for any replies.

Well documented on here. AOS failure=white smoke from exhaust. You are in for an AOS replacement.

Quotes source post: 11906517

+996. To Bdub : check out this video: Porsche 996 air oil separator - YouTube

That is it exactly! Thanks for sharing, bringing it in Monday.

Thanks, I hope the whining noise is associated with this too. Last winter, when the whining noise started, the 'stealership' replaced the serpentine belt and pulleys. Which of course was not the problem. Then I was told it was a fan that blows hot air in to the intake when it is cold. That still might be not working right, because occasionally there is sort of a screeching noise when I start the car. One thing at a time I guess. First, a new AOS!

Hi, What about similar symptoms (the noise) but in a 997.1 GT3? Removing oil cap while the engine's running does not make a change to this noise. Thank you Jacek