996 Turbo Bearing Noise - HELP

eca02apc · 14 Sep 2014

Well I'm rather deflated this evening. My cherished 35k mile 996tt has developed a bearing noise from the engine, most audible from within the cabin, near the rear left seat. It's not easy to hear from the engine bay. It's directly related to engine RPM's and I can reproduce it even when stationary (so it's definitely not a wheel bearing, unfortunately).

Initial hope was that it would be something run by the aux belt, but it doesn't sound like it's from that area at all - I can't even hear the noise when I'm in the vicinity of the aux belt. Like I say, it's loudest when I put my ear to the back of the rear left seat. Very difficult to hear unless inside the cabin.

So what's the prognosis? The only thing I can think of in that area is the timing chain. Could it be one of the camshaft bearings? Or is there another more likely culprit, oil pump maybe?

One thing I haven't checked is whether it makes a difference if the clutch is in or out. I'll have to check. I guess it could be something on the input shaft.

Anybody any thoughts (other than take it to an indy, which I most likely will do)?

kas750 · 14 Sep 2014

I would presume it was something simple..i.e water pump or alternator or something else that is driven by the belt..The only way to tell for sure would be to remove the belt and run the engine for a few seconds.

Also will it make the noise if you rev the car with the clutch pedal depressed?

eca02apc · 14 Sep 2014

But it doesn't sound like its coming from near the belt......

Need to check whether clutch up or clutch down makes a difference.

Andyvvc · 15 Sep 2014

Mine makes a slight chirruping sound from the rear which worried me. Dropped it into OPC Notts - they kept it for a day (wanted to get a cold start up) and told me it was normal oil pump chain noise. They also checked the aux belt and pulleys for me and said they were all fine.

No charge at all! (And i suspect if they had found a fault they would have been open to a little haggling on cost. Nice bunch of people at OPC Notts)

If you are worried you could do worse than book your car in at you local OPC for a professional opinion.

In relation to the noise not sounding like it came from the belts or pulleys - mine was hard to locate too. It wasn't until they had it up on the ramp that they were able to locate the source.

eca02apc · 17 Sep 2014

Ok, I now know it makes no difference clutch up or down, so it's definitely engine not gearbox related. And it really sounds like it's coming from the front of the engine (behind the rear seats).

I have a sinking feeling that the engine's going to have to come out to gain access to whatever it is.

cheshire911 · 18 Sep 2014

Unfortunately with this rear-engined car, there is very little space to work and that is why I always maintain that sometimes the simplest of jobs as we think can require an engine out job to rectify - a lot o hours and a lot of hours = a lot of labour costs!

I'd be inclined to take it to a good reputable indy to let him listen and then decide the next steps from there. I do empathise ith you, anyhting that sounds ominous (and therefore costly!) can have anyone mesmerised like bunny rabbits in the headlights of cars! What if it's this, or what if its that etc. Take the immediate step of having it seen by an expert and good luck. I'll keep my fingers crossed that its a simple fix.

Slutters · 18 Sep 2014

Probably spent so long sitting all the oil has drained away and it takes 10 mins for it circulate when you do eventually start it......

I would get a long screwdriver and put the pointy end on various places to try and find where the noise is coming from.

Mac996t · 19 Sep 2014

As others have said sounds like your best bet will be to take it to a good indy who is familiar with the 996t.

A few thoughts

The 996t engine is very robust so there is a lot more chance of it being something simple rather than serious

The timing chains are all at the rear of the engine ie the aux belt end, as is the intermediate shaft drive which is well known for making noise, if you type intermediate shaft noise into youtube there are a few vids to see if this sounds like the noise you can hear, it doesn't really fit though because usually it sounds the loudest from the rear especially if you listen from ground level in the middle of the bumper.

I can't think of anything located on the engine that could produce a bearing noise from the area you mention are you sure its not coming from the rear passenger speakers, some sort of interference through the stereo maybe?

The main oil pump is located in the lower part of the crankcase towards the front of the engine and can be quite noisy on some cars but usually more of a whirry rattle, the camshafts or lifters can make noise but this is usually more of a ticking noise, same goes for the fuel injectors, can't see how the flywheel could make a bearing noise.

Do you have any ramps because it would be good to see if you can hear it from under the engine?

It would be good to remove the aux belt and start it up as this would rule out the alternator, waterpump, the powersteering pump, the air con pump and the idler and tensioner pulleys, lots of bearings in those.

Another point to mention is that in the past I've been convinced a noise is coming from a certain place only to find it was from another, I once had a car that was making a scraping noise which both me and passengers were 100% was from the front and it turned out to be the handbrake cable rubbing on a rear wheel.

What ever it turns out to be let us know so it doesn't end up as one of those threads with questions but no answers, I'm sure I'm not the only one to hate those LOL

Mac

eca02apc · 23 Sep 2014

Thanks for the responses, it's a big help - a problem shared and all that.

Mac, you could well be right. I can't think of anything in the location it seems to be coming from that would produce the textbook woowoo sound of a failed bearing, so maybe it's being bounced around from somewhere else. I agree that the best thing to do is whip off the aux belt to see if the noise stops. If it does I'll be delighted as then it's only a case of replacing one of those components as opposed to an engine stripdown. If it doesn't then I need to get under the car with a stethoscope. Trouble is, I hate putting it on the wheel ramps I've got and, whilst I've got an inspection pit in a garage in Derbyshire, the car is in Cambridge!

I need a couple of parts from Porsche for unrelated stuff and I also need them to activate the telephone now that I've installed the Dension. So I'm thinking I could pay them £150 for an annual inspection (puts another nice stamp in the book) and ask to have a snoop around for the noise whilst its on their ramps. It's due for a 'service' anyway as it's a year since it's major, although it's only done about 1,000 miles since.

Thanks Slutters, I know I need to drive it more. When I bought it I said I'd use it as my daily during summer and then garage it over winter. The reality is it's turned into far too much of a garage queen! I want to get this issue sorted and then just run it. It doesn't matter where I drive it, even if it's to work and back it still puts a smile on my face.

cheshire911 · 3 Oct 2014

OP - did you get to the bottom of this "turbo bearing noise please help"?

eca02apc · 5 Oct 2014

Not yet. Other things have got in the way so I'm no further along yet. I'll get it on some ramps and have a listen when I get back after my hols.

wizard993 · 5 Oct 2014

From inside the car and when under boost(and only when under boost) if you then get the whine which stops when you come off the boost it's almost certainly a turbo bearing that is starting to fail.

If it whines when the car is at standstill then check the auxbelt pulleys and/or waterpump....spray a small amount of water onto the belt to see if the noise goes away.

If you not losing any water then chances are its not a water pump issue as they tend to leak before the pump bearing whine(they rarely just let got without a noise first).

eca02apc · 21 Oct 2014

Ok, so took the car the OPC Cambridge and had them put it on the ramps. It sounds like it's coming from the rear nearside when stood underneath, so I guess that points to the water pump. The tech and the service manager commented that it was too subtle to be of concern and that I should let it progress to make diagnosis easier! Erm, ok! So not much further forward still. Next bet is to get it up to my parents and over the pit and try to pinpoint with a stethoscope.

Thanks wizard, I was wondering what the symptoms from a turbo would be. It does it regardless of boost pressure and is most noticeable under light throttle at lower RPM's, so hopefully that rules out the turbos.

996 Turbo Bearing Noise - HELP

eca02apc

Nurburgring

kas750

Zandvoort

eca02apc

Nurburgring

Andyvvc

Nurburgring

eca02apc

Nurburgring

cheshire911

Portimao

Slutters

Monza

Mac996t

Hockenheim

eca02apc

Nurburgring

cheshire911

Portimao

eca02apc

Nurburgring

wizard993

Donnington

eca02apc

Nurburgring

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