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Screeching Engine Whistle/Squeal/Whine

 
Old 03-23-2010, 10:59 AM
  #1  
ctrzaska
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Default 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.

Itĺs 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.
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Old 03-23-2010, 11:10 AM
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ivangene
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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
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Old 03-23-2010, 11:15 AM
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Marc Gelefsky
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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
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Old 03-23-2010, 11:50 AM
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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.
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Old 03-23-2010, 12:03 PM
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Barn996
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You may want to consult with a Porsche mechanic if removing your belt as suggested didn't eliminate that noise. GL
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Old 03-23-2010, 12:33 PM
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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
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Old 03-23-2010, 12:38 PM
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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.
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Old 03-23-2010, 12:57 PM
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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)
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Old 03-23-2010, 01:36 PM
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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.)
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Old 03-23-2010, 01:39 PM
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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
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Old 03-23-2010, 01:59 PM
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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.
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Old 03-23-2010, 03:02 PM
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what are the temps in your area lately?

I would suggest a differant oil with the change (but dont want to start that again)
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Old 03-23-2010, 05:06 PM
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Temps are back to normal. Using the 0 has never been an issue in the past, however.
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Old 03-23-2010, 07:01 PM
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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
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Old 03-23-2010, 07:33 PM
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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
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