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Porsche 997S-2005: Screeching noise from Engine

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ajmclean

New member
Hi,

I hope somebody will really help me as i don't know who to turn to.

There is really loud screeching noise coming from fly-wheel engine area. In my desperation i got it towed to a local garage. They said they isolated the engine by removing the gear box and then removed the timing belt and the nose was still there. They didn't remove the fly wheel.

I have upload the video of the noise looking from underneath the car on YouTube. Please have a look.

https://www.youtube.com/watch?v=E670UmV8CMw


I can really do with some advice.

Thanks in advance.
 
mmm timing belt ? i assume that they mean auxiliary drive belt, as your car has a timing chain.

Ordinarily I would suggest removing the drive belt and running the engine to see if the noise goes away.
But if its removed already then that test is no good as the noise is definitely still there.
If it isn't then I would suspect something on this side of things (a/c compressor/slipping belt/ water pump etc)
Do you have a good oil pressure showing, and/or any performance issues, has the oil been checked for contaminants etc
It needs a bit more info before working it out. Such as does the noise change with engine speed, was this a sudden or progressive noise



 
Wow - that's pretty terrible!
If the noise is louder at the flywheel end of the engine, I'd suggest either oil starvation in the crankshaft or more likely, impending failure of the IMS bearing. As you've got an earlier car and the gearbox is off already, the bearing can be inspected / removed / replaced without removing the engine.
Actually hold that thought - listened to the noise in the vid again and I'm now certain this could be a leak in or total failure of the Air-Oil Separator (AOS)
 
Thanks for your reply.

In the video belt is still on but the mechanic said the noise was still there without it. Didn't notice any performance issues however i drove less than 30mph for a few hundred meters before the mechanic.

The mechanic just told me that apparently it needs an engine rebuilt or at the very least open up the engine to identify the noise. I am however sceptical because i thought that would hear a different noise if it need a rebuilt also this noise comes after 10mins from a cold start.
 
I had the IMS bearing upgraded 3 years ago. Just to let you know there was no white smoke from my exhaust so can it still be the AOS issue?
 
Sorry, I don't have any suggestions as to what it might be but the sound continues on for about 1 second after the flywheel has stopped at the end of the video (or is the sound out of sync?). Assuming noise continues for a bit after engine has stopped then surely that rules out the majority of the rotating/reciprocating engine internals.
I would have thought the idea from STiG911 about oil separator is certainly a candidate.

Please do keep us informed of any progress.
 
Thanks guys. I will keep this post updated. I think i need to move the car to different mechanic because hes quite persistent he needs to open up the engine. That could cost me a fortune.
 
If its running ok, with no loss of performance and no obvious signs of impending failure (oil in water, loss of oil pressure, no engine lights, etc) then i would think twice about stripping it down without checking the obvious other candidates that could cause the noise.
Yes it could be bearing noise - but this could be from a source external to the engine such as the water pump or alternator, or even the drive belt about to disintegrate.
If the noise was caused by an internal bearing the oil and oil filter would tell the story - they would be full of metal fragments.
Think I'd be a bit concerned about a mechanic that tells me it needs an engine rebuild, then says at the very least needs to be opened up.
How exactly does he know this if he hasn't identified the problem.
Good luck
 
If it is the air/oil separator causing excessive vacuum in the engine then removing the oil filler cap or dipstick whilst running may make the sound disappear. Engine will run rough though.

If you keep playing the end of the video from 22 seconds onwards you will see the flywheel is stationary but the noise is there. Noise lasts till 23 seconds as it decays away. This must be a vacuum related issue.

I would not let them take my engine apart!
 
Wow!
If it was engine internals the engine would eventually seize...or do some nasty explosion and it would be there from start of engine and stop when engine stop.
Too bad he didn't show the belt on the pulleys and off the pulleys. Could be the pressure plate sticking or bits broke off and screeching against the fly wheel? Noise wasn't there initially when car started and then continues after car stopped?... if it was internal engine parts surely it would be from beginning. I would feel engine OK.

Only you say auxiliary belt was checked... I would still be thinking pulley.
 
I just re-read your post "the noise comes ten minutes from a cold start" if this were a mechanical failure in the engine chances are it would be present from startup, unless a heat related crack or bearing starvation - again both of these would be obvious from examining the oil/filter.
I'd get a second opinion on this one.
 
That mechanic is a joker. Is he supporting the rear of the car on bricks? Needs rebuilding? Why? Has he even seen a porsche before? Take it away from his hands ASAP!

Take it to a specialist and don't be too concerned, I doubt it's anything serious, and it won't be the IMS or it's impending explosion, that's not how they go. I very much doubt the engine needs rebuilding.

As as others have said, auxiliary belt, AOS or fan will be your first ports of call.
 
Another thought:- does the screech pitch alter when the steering wheel is turned?
If so, it might be a dry power-steering pump.
Regards,
Clive
 
Is the noise there when the engine is revved? Only at idle in the video. Also, as has been pointed out earlier, the sounds fades away rather than just stopping when the engine is switched off.
This from another forum
Air Oil Separator: The oil re-breather system on the 997 circulates through a membrane which acts to filter out oil which is caused by blow by from the engines crank case. This system over time deteriorates and causes two symptoms to crop up. The first is white smoke on start up which initially will be observed intermittently. If the AOS gives out completely in some cases there will be white smoke continuously. The second symptom is also upon start up and is a high pitch whining sound. The sound is often miss diagnosed as a potential pulley bearing failure, or the belt itself needing to be replaced. Instead of either of these issues it is actually the rear main seal (RMS) allowing a vacuum leak. As you can imagine this is not desirable and can in the long term damage the RMS.


Also, play the video in the first post on this thread
https://rennlist.com/forums/996-forum/557533-screeching-engine-whistle-squeal-whine.html

Sound familiar?!

Then read post #21 on the same thread on page 2..............
 
Run the engine with the oil filler cap off, I bet the sound either is no more or greatly changes. High pressure in the crack case.
 
I'd go with air oil separator, the fact that it continues after the engine is switched off I think is significant, something is act like a 'reed' (clarinet style) due to vacuum.
 
Here's an update for you guys. I took your advice and had the car towed to a specialist. It was the AOS - It cost me £100 for the part and £200 labour. A little different to an engine rebuild that the original mechanic advised.

I would like to thank every one of you for your feedback, support and guidance for what was quite a stressful period whilst trying to sort this problem out.
 
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