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infrasilver
Fast & Furious
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2001 Porsche 996 Targa

PostPosted: Thu Dec 24, 2015 2:09 pm    Post subject: Reply with quote

The shaft I have from Hartech is a lot thicker than standard and I recommend getting it changed if you change the bearing. The standard one can get weakened by removing the cover and re-tightening, it's still a known weak point, sometimes overlooked.


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alex yates
Shanghai
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2000 Porsche 996 Carrera 4

PostPosted: Thu Dec 24, 2015 2:33 pm    Post subject: Reply with quote

I would've deffo done that if I was removing the bearing. The fact that OPC scored all the seal on one side of the plate refitting it put the frighteners on me.

I'd probably make my own if I did one with something like an M18 thread on with no undercut.
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jm24
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PostPosted: Sun Dec 27, 2015 11:00 pm    Post subject: Reply with quote

Do you think the mileage estimates on bearing failure probabilities vary much with age, and if so how? Surely a car that does 50k over say 4 years will have a very different effect on the grease displacement etc that one that does 50k over say 10 years + ?
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alex yates
Shanghai
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PostPosted: Sun Dec 27, 2015 11:06 pm    Post subject: Reply with quote

Infant mortality - nuff said.

https://en.wikipedia.org/wiki/Bathtub_curve
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Niall996
Imola


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PostPosted: Mon Dec 28, 2015 2:36 am    Post subject: Reply with quote

The view of Road & Track Magazine. More odd 'stuff' on the IMSB - e.g. "a short run of low capacity bearings, 'some' of which ended up in early 996's."

"The biggest reason for low 996 values is the misconception that the engines have the durability of blown glass. This is one gripe with the 996 that really needs to be addressed. Some early cars featured a weak bearing in the intermediate shaft, known as the IMS. Porsche has used an IMS in its 2.0-liter engines since 1965. The IMS drives the camshafts indirectly off the crankshaft. But even before the introduction of the 996, Porsche had experimented with new bearing designs, and this development resulted in a short run of low-capacity bearings, some of which ended up in early 996's. An IMS bearing failure results in a completely destroyed engine. Luckily, most qualified Porsche shops can perform a pre-purchase inspection and identify bearings that have been upgraded or may need to be replaced.

As terrible as a blown engine is, enthusiasts have made it seem like every 996 came with a defective engine. Further fanning the flames, Porsche's handling of the problem was a PR disaster. But the reality is that the majority of the engines are fine. "Engine failures in [engine model] M96 in actual real numbers range from one to five percent," Brownell says. "It's more than there really should be, but it's not quite as dire a situation as the Internet would have you believe." What's more, the problem can be corrected by a $400-$700 upgrade."
 
  
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alex yates
Shanghai
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2000 Porsche 996 Carrera 4

PostPosted: Mon Dec 28, 2015 7:45 am    Post subject: Reply with quote

Niall996 wrote:
Luckily, most qualified Porsche shops can perform a pre-purchase inspection and identify bearings that have been upgraded or may need to be replaced.


Don't believe everything you read - this comment is blatantly untrue. Just goes to show journalists are not mechanics. The only way to identify anything with the ims bearing is to remove the gearbox and strip the cover plate off. No ppi will do this. nooo
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New997buyer
Yas Marina


Joined: 17 Oct 2010
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PostPosted: Mon Dec 28, 2015 9:50 am    Post subject: Reply with quote

alex yates wrote:
Niall996 wrote:
Luckily, most qualified Porsche shops can perform a pre-purchase inspection and identify bearings that have been upgraded or may need to be replaced.


Don't believe everything you read - this comment is blatantly untrue. Just goes to show journalists are not mechanics. The only way to identify anything with the ims bearing is to remove the gearbox and strip the cover plate off. No ppi will do this. nooo


I agree with the first and last part of this statement. The middle bit not so much. It doesn't 'show' anything. Some of the technical details are not right in the 'Road and Track' article, but some of the rest of the judgement, thinking and advice in it is spot on IMHO.

Technicians have greater tacit knowledge, sure, but being human they're just as prone to bias and judgement errors when dealing with matters like IMSB. So while they may be more technically accurate they will still need treated with scepticism as they can be written with all sorts of unconscious biases influencing thier views. Most will are either defending an opinion or selling an idea.

And that isn't being disrespectful to mechanics or engineers. But just like economists, historians or any profession, get 10 in a room regarding complex matters like 'bore score' or 'IMSB' and you'll get 11 different answers.

Baz from Hartech is the closest I've seen yet to someone in this debate who's not just put in the work, but also the method and systems to support better judgement to base his claims on. That's why there can be greater confidence in what he posts, IMHO.

And it's why I disagree with the binary and frankly simplistic assertion that because mechanics or technicians have experience they're therefore 'right' and journalists are always 'wrong'. When it comes to complex matters each needs handled with care.
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alex yates
Shanghai
Shanghai


Joined: 06 Mar 2014
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2000 Porsche 996 Carrera 4

PostPosted: Mon Dec 28, 2015 10:25 am    Post subject: Reply with quote

Point I was getting at Paul is people read these articles and think that it's the gospel truth when in fact it's more a case of the author (for whatever reason) not understanding what he is writing about and has more likely got bore scope checks for scored bores mixed in with his comment about checking the ims bearing on a ppi.

It's a real shame as some potential purchasers may think it's ok, if I get a ppi done, then the ims bearing will be fine, when both you & I know that is far from the case.

There's more truth in you favourite rag - the 'Daily Fail' Laughing

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alex yates
Shanghai
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2000 Porsche 996 Carrera 4

PostPosted: Mon Dec 28, 2015 10:28 am    Post subject: Reply with quote

No specialist Indy that I'm aware of (including all of them) will tell you the ims bearing can be checked on a ppi.
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Chris_in_the_UK
Paul Ricard


Joined: 19 Mar 2014
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PostPosted: Mon Dec 28, 2015 11:00 am    Post subject: Reply with quote

alex yates wrote:
No specialist Indy that I'm aware of (including all of them) will tell you the ims bearing can be checked on a ppi.


There may be documentary evidence in the for of a receipt/invoice if it's been changed or looked at during clutch replacement.

But here is another dynamic..........

What if there is a receipt to say it's been changed - would you take comfort if it was an LN one? What if it's been done and a standard bearing has been fitted with a hammer?.

Dont know

Personally I think it might be preferable if one has not been changed which then gives you the options being discussed in this thread.
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alex yates
Shanghai
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2000 Porsche 996 Carrera 4

PostPosted: Mon Dec 28, 2015 11:04 am    Post subject: Reply with quote

All I wanted to see in my bills & receipts before any dosh was parted with was:


Mobil 1
Mobil 1
Mobil 1
Mobil 1
Mobil 1
Mobil 1

Smile

At the time though, I was very naive to the 996 and would've welcomed a bill that said ims bearing upgraded, even though OPC won't ever do this job (as far as I'm aware).
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Chris_in_the_UK
Paul Ricard


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PostPosted: Mon Dec 28, 2015 11:07 am    Post subject: Reply with quote

alex yates wrote:


At the time though, I was very naive to the 996 and would've welcomed a bill that said ims bearing upgraded, even though OPC won't ever do this job (as far as I'm aware).


Comes as an 'assembly' - AKA replacement engine!.
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New997buyer
Yas Marina


Joined: 17 Oct 2010
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PostPosted: Mon Dec 28, 2015 11:11 am    Post subject: Reply with quote

Thing is even the most sorted and mint 996.1 is still only going to be a £12-15k motor. If anyone was worried they could get a full Hartech strip and rebuild for £12-14k. That's still an appreciation proof icon you can use everyday.

All this fear/prejudice is keeping us 996 owners out of the self regard threads of the air-cooled world. But at least it's keeping 911 motoring accessible Dont know
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Niall996
Imola


Joined: 07 Nov 2010
Posts: 828
Location: Paris


PostPosted: Mon Dec 28, 2015 11:50 am    Post subject: Reply with quote

New996buyer wrote:
Thing is even the most sorted and mint 996.1 is still only going to be a £12-15k motor. If anyone was worried they could get a full Hartech strip and rebuild for £12-14k. That's still an appreciation proof icon you can use everyday.

All this fear/prejudice is keeping us 996 owners out of the self regard threads of the air-cooled world. But at least it's keeping 911 motoring accessible Dont know


Or you could buy one of these little components and pop it in!

http://www.ebay.com/itm/Porsche-996-GT-3-engine-381-hp-/221976527988?hash=item33aed50474:g:~EsAAOSwcOFWbg2c&vxp=mtr

I wish! Seriously though, I never expected the thread to go so deep. And I'm actually still pretty unsure about it all. It's a bit like one step forwards two steps back. You think you've gotten to a point of resolution and then another angle or nuance appears from somewhere. I know Baz is held in very high esteem here and I don't question that. Thumbs up for Baz and Hartech. But for someone of my limited technical knowledge, he's just too far out there for me. I realy struggle to get a definitive layman's understanding from his posts as they tend to be very long and full of all sorts of mechanical and engineering concepts, theories and phrases. A delight for engineers and the mechanically savvy DIY'ers no doubt. But not for me and I suspect a few others of the no idea what's going on under the hood brigade. It's a bit like asking the top speed of the car and getting all sorts of potentialities and variables regarding angle of road surface, resistance of rad surface, density of traffic, wind resistance and latent atmospheric temperature measurables! I just want to know the top trump answer, 174mph. (Give or take).

I would love to see someone more capable than me pull it al together in a sort of sticky thread, one that has real consensus and then leave it there once and for all. I've learnt some thinks in this thread and have become a lot more aware of the general discussion about what the best option for owners which is the real point of this thread.

So there are different needs for different eras. The right option for a 3.4 dual row bearing owner is not necessarily the same course of action that a 997 'big bearing' owner would be looking at. Yet the IMSB discussion tends to lump them all together.

I think what I'd love to see is a sort of universally agreed excel sheet with the different engine formats, 3.4 (1), 3.4 (2 -if there was a change), 3.6.1, 3.6.2 (if there was a change), 997.1, 997.2 and a sort of drop down micro menu that says something like (and I'm making this up for the sake of argument).

3.4.1 Dual Row Bearing. 98% reliable. no need for random check until 140K miles. Remove dust shield. Change oil every 5K miles. Check with clutch change, replace with new bigger single row (Porsche Standard Part). unless it's clearly still perfect.Stay away from x,y,z...

3.6.1 Single Row. 90% reliable. Need to check before 90K. Unless perfect, change to large Single Row (Porsche standard part). Change oil every 5K.Stay away from x,y,z....

3.6.2 (is this the 997.1?) IMSB is locked inside casing.You're options are x,y,z.. Stay away from x,y,z...

In fact a little app would be cool but a definitive sticky thread would do! All endorsed by the likes of Hartech, Autofarm and whoever else who does this type of remedial or preventative work.....

And then, the idea is that it's all out there. Everyone sees the real transparent simplified version of it and knows exactly where they stand and what they need to do, what they should do and what they shouldn't do. And I think when we get to that point, the engine issue with 996's will be over once and for all and the world can start to talk about how brilliant the car actually is and always has been. So I'm happy for the real egg heads on here to bang heads with the techno wizards at Hartech and whomever, and create the definitive one pager and I'll keep asking stupid questions whenever the lingo gets a bit techie. In actual fact, if people had more confidence in terms of the best course of action, owners would be much more likely to spend a few bob and get stuff done. I think what inhibits a lot of is is not wanting to get caught up in the 'apparent' snake oil sales pitch.
 
  
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Chris_in_the_UK
Paul Ricard


Joined: 19 Mar 2014
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PostPosted: Mon Dec 28, 2015 12:24 pm    Post subject: Reply with quote

For me (as somebody with reasonable technical comprehension) it is not hugely complicated but I understand how it could be.

I doubt you will get that level of 'definitives' due to a few reasons:-

Manufacturers really keep detailed build history so where changes occurred in respect of a vehicle run would be difficult to pin down to a range of engine numbers.

Sometimes manufacturers source the same parts from different sources so it might be that the issue is with one supplier not all suppliers.

Nobody will be brave enough to give a definitive mileage other than a gut feeling from sales they have worked on (Baz already has done).

It's a free market - snake oil salesmen love free markets!....

Cars break, $hit happens.
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infrasilver
Fast & Furious
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2001 Porsche 996 Targa

PostPosted: Mon Dec 28, 2015 12:40 pm    Post subject: Reply with quote

To help people understand a little more, I usually post pictures from my previous rebuilds, I think this helps to get a better idea of what is being talked about.
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Niall996
Imola


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PostPosted: Mon Dec 28, 2015 1:06 pm    Post subject: Reply with quote

Chris_in_the_UK wrote:
For me (as somebody with reasonable technical comprehension) it is not hugely complicated but I understand how it could be.

I doubt you will get that level of 'definitives' due to a few reasons:-

Manufacturers really keep detailed build history so where changes occurred in respect of a vehicle run would be difficult to pin down to a range of engine numbers.

Sometimes manufacturers source the same parts from different sources so it might be that the issue is with one supplier not all suppliers.

Nobody will be brave enough to give a definitive mileage other than a gut feeling from sales they have worked on (Baz already has done).

It's a free market - snake oil salesmen love free markets!....

Cars break, $hit happens.



You know, it's not that I'm worried about my car. It's only at 80K miles and has a long way to go before it'll need big work by which time I'll be delighted to do a lovely shiny new engine rebuild/refresh. Can't wait!
My initial motivation at the beginning of of the thread was seeing the DOF video and thinking, hey, why not, that looks like a good thing. I'll just pop into 911Uk and get a sense check, maybe someone has got it done etc. But I think as the thread has progressed my motivation has changed. There is so much contradiction and confusion out there (as evidenced by top magazines pumping out alternative myths) that it's the contradictions and myths that are the real problem, not the bloody bearing So I'm now on a bit of a mission now to get to the bottom of it all for the sake of clarity, somehow, someday and hopefully we'll see the end of the IMS threads!

Just to give one example of an ongoing prevailing contradiction. There are at least five distinct versions of the IMS bearing core problem itself that I can make out.

There is:

A) One off random batch of bad ones theory. Luck of the draw. (Road & Track et al).
B) Theory that the bearing itself wan't built strong enough. (Porsche's own theory apparently).
C) Theory that the bearing is perfectly good but it's not lubricated properly. (DOF theory, dust shields, etc).
D) Manufacturing variance theory. Not so much a bad batch but just a sort of one in every hundred IMSB's comes off the production line somewhat less than perfect (in which way no one knows though).
E) Random theoretical combination of all three above. ie. No one knows theory. (New bearings, DOF, how you drive, how you start the car, which brand of oil you use, anything and everything kitchen sink theory etc etc etc...) (Or, in some cars it's a bd batch issue, in others its how you drive, in others its poor lubrication and so on)

Each of the theories raises all sorts of secondary issues. The right fix for one can be the wrong fix for another. Or each has separate conflicting implications. If we could even get agreement on just this one thing alone it would solve 90% of the whole IMSB saga! Bad batch or bad bearing or bad lubrication? With all the dozens of posts and threads and magazine articles I've seen, I keep coming across different variables on this theme. You would think by now it would be well an truly nailed. Did the US class action specify what the core issue was by any chance?

If I was to proffer an uneducated guess I would say that I'm not convinced by the lubrication thing because all cars are essentially the same so they'd have all failed. Bearings would be failing right left and centre. I'm not convinced by the production variance because it's not that complicated a component. I can't imagine there being any real difference between every twentieth bearing and the rest. I'm not convinced by the bearing was never designed correctly in the first place. Seeing at 90-95% of cars have worked perfectly well it seems the design was fine. Maybe the bad batch theory makes most sense then. A bunch of engines popped and that's basically it now? In which case any decent replacement is a good option. I don't know!
 
  
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Niall996
Imola


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PostPosted: Mon Dec 28, 2015 6:14 pm    Post subject: Reply with quote

infrasilver wrote:
The shaft I have from Hartech is a lot thicker than standard and I recommend getting it changed if you change the bearing. The standard one can get weakened by removing the cover and re-tightening, it's still a known weak point, sometimes overlooked.



Do Hartech supply the whole shaft and bearing thingy to anyone or do they only install it themselves? Sounds like an interesting option during a clutch change. Have you ever heard anyone express a downside to it?
 
  
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infrasilver
Fast & Furious
Fast & Furious


Joined: 04 Oct 2010
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2001 Porsche 996 Targa

PostPosted: Mon Dec 28, 2015 6:41 pm    Post subject: Reply with quote

I gave them my IMS and they fitted the bearing and shaft, I just refitted the whole assembly into the crankcases.
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jm24
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PostPosted: Mon Jan 04, 2016 2:46 pm    Post subject: Reply with quote

Had the car up on a ramp over the weekend so checked and changed the oil filter for any signs of particles. At first it looked like there were but then realised was just a few small bubbles. Had a thorough look through and nothing in there at all. Wink
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