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Niall996
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Joined: 07 Nov 2010
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PostPosted: Tue Dec 08, 2015 9:51 pm    Post subject: Finally, IMS, is this the answer and ultimate closure. Reply with quote

https://m.youtube.com/watch?v=hzUq2DFpeKw

Found this video on direct oil feed. It was recommended by a local well respected independent in Cape Town, a real genuine Porsche hub all things Porsche from racers to road cars across all eras and models. All in, 1200 quid to source and install. What does the forum think?
 
  
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drabux
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PostPosted: Tue Dec 08, 2015 10:05 pm    Post subject: Reply with quote

I seem to remember a much cheaper 'direct oil feed' solution which involves drilling a small hole into a nearby oil passage.

Some people have cast doubt on these solutions saying that the oil will spin out under high rpm, unlike the grease that is usually encased within the dust shields.
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alex yates
Shanghai
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2000 Porsche 996 Carrera 4

PostPosted: Tue Dec 08, 2015 10:09 pm    Post subject: Reply with quote

News Flash: Titanic hits Iceberg. Smile


The IMS bearing has a direct oil feed - all you need to do is remove the dust shields. Proven by Hartech.
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plynchy
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PostPosted: Tue Dec 08, 2015 10:12 pm    Post subject: Reply with quote

Loads of text on this subject in 911 & Porsche World this month.

Interesting reading.
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Niall996
Imola


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PostPosted: Tue Dec 08, 2015 10:36 pm    Post subject: Reply with quote

alex yates wrote:
News Flash: Titanic hits Iceberg. Smile


The IMS bearing has a direct oil feed - all you need to do is remove the dust shields. Proven by Hartech.


So according to Hartech, all you need to do is remove a dust shield?
 
  
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Poker2009
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PostPosted: Tue Dec 08, 2015 11:05 pm    Post subject: Reply with quote

When I had the clutch changed, I got the garage to remove the the IMS bearing outer seal (round plastic cover), it was already slightly worn, and was letting some oil in. Car had done about 40k miles and was nine years old at the time.
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alex yates
Shanghai
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2000 Porsche 996 Carrera 4

PostPosted: Tue Dec 08, 2015 11:47 pm    Post subject: Reply with quote

Niall996 wrote:
alex yates wrote:
News Flash: Titanic hits Iceberg. Smile


The IMS bearing has a direct oil feed - all you need to do is remove the dust shields. Proven by Hartech.


So according to Hartech, all you need to do is remove a dust shield?
YES
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RyDog
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Joined: 22 May 2014
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PostPosted: Wed Dec 09, 2015 12:11 am    Post subject: Reply with quote

alex yates wrote:
Niall996 wrote:
alex yates wrote:
News Flash: Titanic hits Iceberg. Smile


The IMS bearing has a direct oil feed - all you need to do is remove the dust shields. Proven by Hartech.


So according to Hartech, all you need to do is remove a dust shield?
YES


...and Alex comes back with a classic uppercut response Pop Corn
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Chris_in_the_UK
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PostPosted: Wed Dec 09, 2015 1:37 am    Post subject: Reply with quote

One of a few \smoke and mirrors' solutions.
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Niall996
Imola


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PostPosted: Wed Dec 09, 2015 9:17 am    Post subject: Reply with quote

Chris_in_the_UK wrote:
One of a few \smoke and mirrors' solutions.


Why is it a smoke an mirror solution? What specifically do you mean?

This local independent, a highly reputable independent amongst the Porsche community in Western Cape is advocating it strongly.

http://lynxmotorsport.co.za/#&panel1-2
 
  
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bazhart
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PostPosted: Wed Dec 09, 2015 9:55 am    Post subject: Reply with quote

To try and answer why there are different solutions.

A ball bearing does not benefit from a pressurised oil feed it just needs a supply of fresh cool oil and to be part of a filter system to remove and small pieces of worn metal that inevitably wears off parts slowly. A linear shell bearing does need a pressurised oil supply to keep the shaft metal apart from the shell bearing material as a result of the pressure in the oil between them - without which it could seize.

The sprocket diameter on the end of the shaft runs in an oil bath at up to around 4,500 rpm and the chain fitting round it also travels at up to 40mph in the same oil bath - these between them splash oil in all directions at enormous force and speed and it gets everywhere and is entirely capable of lubricating an open ball bearing nearby.

In fact when the dust seal that Porsche fit has worn slightly and the grease has leaked out - the pressure and force of oil nearby is sufficient to get in and out of that minute seal lip and in most cases can lubricate the bearing sufficiently to last for up to 150K (if it was not damaged too much during the period the grease mixed with wear particles, eventually escaped and the seal lip was worn enough by then to allow oil to seep in again). You can imagine how much better that would be if the whole seal was removed.

The test set up of a bearing rotating in an oil bath does not describe the actual process as the centre of the IMS bearing remains stationary and it is the outside race that rotates. it is true that a rotating disc will throw oil outwards under centripetal acceleration but the gear is many time larger than the bearing running directly in the sump oil bath and the chain running at high speed in the same oil bath throws oil against the crankcase wall where is splashes in ample quantities with much more force and volume that the small IMS bearing does in the opposite direction and so - it is entirely sufficient to lubricate the bearing.

Furthermore that oil bath is a continually cooled source of fresh filtered oil - nothing more needed.

The small bearing itself is just slightly under a spec that would make it reliable for 100% of all fitted with it in this application - so perhaps 99.5% reliable say but with the seal in place that reduces to perhaps 90% or so.

Lots of IMS products are s old as upgrades but in our opinion the only true "upgrade" is to fit the Porsche shaft with the larger bearing or some other modified original IMS that does so. The larger later bearing is man enough for the job but once again benefits from removal of the seal on assembly - which we do during rebuilds.

Baz
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alex yates
Shanghai
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PostPosted: Wed Dec 09, 2015 9:58 am    Post subject: Reply with quote

Start with reading this post from start to finish:

http://911uk.com/viewtopic.php?t=100752

What folk fail to grasp is any roller/ball/etc. type bearing needs a fraction of the oil that a solid bearing (crankshaft bearings, etc.) need as there is no friction involved to the extent there is with solid bearings (parts roll against each other rather than rub) so the bearing need very minimum amount of oil to survive.


but most importantly of all, read this bit:

bazhart wrote:
We can only generalise and there are always exceptions often providing false feedback because at any moment in time the majority of owners of a particular model will have covered similar average mileages and therefore their experiences will probably be similar.

When the bearing seal has worn more over time the amount of oil that can enter and exit the bearing increases - so it receives a more suitable lubrication.

Consequently when new it is entirely lubricated by grease and the amount of wear particles trapped in the grease varies with the fit of the bearing. Grease filled bearings ideally should have that grease replaced as a matter of normal routine maintenance but of course do not.

The bearing can fail before the grease has run out through grinding away of the resulting mixture of grease and metal. These failures are typically under 50K.

If the clearance allows it to create less particles and it survives the next critical period is when the oil starts to enter the bearing and slowly wash out the grease - after which the volume of oil entering and exiting determines the reliability - another critical point around 70K.

If it survives that it enjoys a period of time when the seal allows plenty of oil in and out and depending on the state of the bearing at that time - it can last up to 150K.

Logic must surely tell you that if the tube behind the bearing can fill up with acidic oil (as claimed) despite the fact that the bearing apparently expels all the oil through centrifugal force (of which the tube itself is effectively a rotating pump) then the forces throwing oil at the seal area of the bearing must be greater than those forcing the oil out again.

The fact that the tube can fill with old oil demonstrates the capability of the free flowing splash oil to penetrate the bearing.

So - without a seal in place - you not only remove any acidic residues or oil (and any wear particles) but also maintain a perfectly adequate flow of fresh oil to the bearing.

I am not sure that new engines that replaced early engines were in fact fitted with larger bearings as for a start - there is not an IMS available with the original roller chain sprockets fitted with the larger bearing and the crankshafts would also to have been chained (perhaps someone can confirm this).

I don't think we have experienced a failure of the larger bearing despite it still being fitted with seals and grease!

Baz



and also this from another post:

(there's loads more from Baz on here but can't find everything)

bazhart wrote:
Since the question has been asked - here are some cobbled together extracts from other postings on the subject that contain a lot of technical information about the problem and our solution. Because I DON’T HAVE TIME TO EDIT THE CONTENT IT MAY REPEAT DETAILS A BIT SORRY!
The positioning of the intermediate shaft long ways is maintained by the bearing press fit. Although it has a small wire circlip in a groove but this can be overcome to remove the bearing by shock loading and it is mainly the interference fit that holds it in place (the clip later changed to a circlip).

New bearings arrived for assembly with grease inside and seals on both outsides. There is no way for oil to pass in or out of the bearing initially. While grease is OK for lubrication at the loads I have calculated and the revs - a heavy interference fit on both the inside and the outside of the bearing results in the balls inside grinding some minute particles of metal away as they "run in". I think everyone knows that when running in you usually have to change oil to remove those initial wear particles while an engine settles in - but there is no way this happens in this bearing - which is perfectly adequate for the loads applied to it - given sensible lubrication so IMHO a more expensive bearing is not neccessary (just the right spec and clearance) and we have had none fail in years of modifying and replacing them and to three figure numbers.

We do not fit seals because with fresh oil being thrown in the direction of this bearing by the two chains nearby running in an oil bath in the sump area - at up to 40mph - there is plenty of potential lubrication available and as the ball tracks are hollow there would always be sufficient oil sat in the bottom of the groove to accommodate initial start up – and now fresh clean oil will be present.

Some we have replaced early have a mixture of grease and oil and what looks like grinding paste inside the bearing and with two ball tracks in the earlier bearing the amount is - suprisingly large. The single row bearing specs up slightly better than the double row because the double row has less deep ball tracks – so the replacement is actually probably better and of course half the metallic particles to wear away.

There is also no cooling since no oil flows in or out.

It seems to me that some are tighter than others (normal mix of manufacturing tolerances will allow a small number to have the tightest fit on both inside and outside while most are less tight) and of course some will run hotter than others while manufacturing tolerances will result in some actual bearings needing more running in (and creating more metal particles) than others.

Most survive until the seal wears and allows some oil in which mixes with the grease forming a type of grinding paste and later on as the seal edge suffers it washes some grease and particles out and eventually works more like the seal was not there in the first place. How soon this happens is again a function of the tolerances and use.

Therefore some - once they get past say 50K or so – generally improve and therefore last a long time (the loads are low - the other end of the shaft which has one chain running against it s just a steel diameter in an alloy hole).

We have seen some in which the ball cage has cracked and although the balls rotate in the same direction – when they crowd together the face of the balls runs in the opposite direction to the next ball so the surface of the balls run against each other at twice the speed that the balls are rotating at and wear rates increase dramatically increasing wear particles. Others have actually cracked the outer bearing housing through metal fatigue (clearly marked) implying that they simply ran too tight for too long or the lack of a cage and the balls crowding over one side of the track overloads the outer race.

Because the spindle is such a basically poor design with a very weak centre - this then often snaps.

By removing the seals - most bearings should be OK since the grease is quickly replaced by the oil and the wear particles can escape and be collected by the magnet or filter. However while removing the bearing in situ is possible (and we have a tool to do so safely) replacing it strains the weak original spindle and could cause a fatigue crack initiation - so a stronger design of spindle should be used to reassemble it. It is also necessary to take off both chain tensioners to avoid the chain load forcing the IMS over too much to one side and expecting the spindle and housing to force it back against the hydraulic tensioners. This obviously takes longer. We also change oil and filter at the same time and usually the RMS.

In my view there was nothing wrong with the idea of an IMS - only the basic engineering thinking was flawed - but then only enough to fail in very small numbers statistically - so not an absolute disaster.

What amazes me more than anything else however is how simple the IMS problem was to analyse and fix and how long it remained a weak spot despite several re-designs - none of which addressed the obvious cause - the need for a tight fit and the lack of proper lubrication resulting from the seals.

By repairing them for those that cannot afford a new engine - we actually IMHO help preserve the confidence of owners and the reputation and value of the cars.

We mainly deal with cars over 4 years old and so have to deal with owners with generally smaller financial resources – than those buying brand new cars and changing every three years.

To do that better than anyone else we introduced our Lifetime Maintenance Plan 10 years ago (well ahead of the market) and invested in engineering solutions, equipment, space and staff - to enable less well off owners to afford to keep their cars - even if and when they become one of the small in number whose experience is devastated by a failure that could have so easily been avoided.

There is no other UK business offering anything like as comprehensive a warranty, nor anything like the quality and variety of repair solutions or the ability and willingness to adjust rebuilds to suit the pocket and future intentions of the owner.



I did contact the manufacturer to buy replacement bearings – which were out of production but in the course of the conversation they confirmed that they too do not understand why Porsche sealed the bearing and recommended they did not. Furthermore- any engineer who is familiar with engines will know that a grease filled bearing inside an engine will gradually lose its grease and then run on the oil. The debris trapped inside and mixed with the grease initially and with old oil later on – prematurely wears the seal edges to allow the grease/sludge to seep out and new oil to seep in and then sit there.

We have seen a failure of a later M97 engine IMS but it is rare – however a larger bearing will resist contracting as much under an interference fit and has more space for more grease and for more contaminants to spread. Similarly we have seen the gearbox bearings (which are also sealed) fail.

I do not expect every IMS bearing to fail and I don’t think that this failure is related to use or even servicing and I believe it is entirely random for the good engineering reasons I previously stated about the quality of the bearing and the build- up of tolerances and have even explained why after say 50K they become more reliable again..

The bearing is a sealed for life bearing but they are not sealed for life when running in hot oil and that is the mistake IMHO. Indeed when you remove the bearing some very black old oil mixed with metal particles slowly drips out of the IMS tube in which it was trapped on the inside of the seal and bearing.

On inspection of those within the danger zone – some lower mileage ones have a mixture of old oil and grease and metallic particles like a grinding paste inside, older ones just have old oil and particles and very old ones have just old oil left.

Clearly oil slowly ingresses and mixes first with the grease and particles and later washes the grease away just remaining as old oil mixed with particles.

A heavy interference fit will inevitably vary from part to part as will the fit and quality of the bearings – so some have a build up of poor quality and tight fit while others may be of better quality and a loser fit – most somewhere in the middle. Some will be run in slowly and others more aggressively and oil changes may be more or less frequent. We simply don’t know if this has any influence or not but out if it all some fail and most do not. It is a marginal design and removing the seal and allowing fresh oil to wash out the running in particles and keep it cool and properly lubricated – is the best improvement.

I have wondered if the seal is to protect bearings and pre-assembled components lining up for mass production – but it should have been removed on assembly.

Numbers are however minute – it is not such a big technical failing – so therefore – to come back to exactly where I started from – my advice is just get some cover that you can afford to protect you from the cost of a failure – just like you do for house insurance and car theft etc.

Eventually all the grease has mixed with the oil and become entrapped in the tube leaving very old oil mixed with bits of metal trying to lubricate the now prematurely worn bearing with minute spots of new fresh oil gradually seeping in.

Once a new bearing has been fitted without a seal (of whatever type and quality) I would always promote the best oil you can afford and more importantly changing it often. My only argument is that I don't see changing oil quality making any difference if the original bearing and seals are still in place because the problem mix that is already trapped within the bearing as it came from the factory is still in there and if you are going to take it to bits to clean it you may as well change the bearing and leave out the seal - after which I believe std oil types are perfectly OK..

A better quality product is always better than a lower quality one but more expensive and if it is unnecessary the extra cost is wasted. The question is always - is it necessary to fulfil the function. In my view and engineering experience and the evidence of those we have repaired – the std replacement bearing of the right grade fitted with the stronger spindle is perfectly up to the job, has proven to be OK and we guarantee it anyway. The problem was never the specification of the bearing but was the insistence of fitting it with seals that appear to have actually caused the problem in the first place.

All parts are made to minutely different sizes and inevitably sometimes you get the largest pin going in the smallest bearing hole in which the inner track is big and the outer track small with the biggest balls in it and fitting into a housing that is the smallest. The odds against it all working one way are huge and therefore the number of "tight" fits is low - but it does happen and likely to present more of a running in problem and more debris to contend with. The amount of grease in there also probably varies - all leading to a small number of failures simply because the design is IMHO marginal.

Bearings are available in a variety of fits or tightnesses and when an interference fit is in use the designer should chose the right one for the application. We have made our choice and we find it works OK.

I will try and attach some photos but if they do not appear and someone sends me an E-mail address who can display them I will send them on to them.
Baz
[/b]
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alex yates
Shanghai
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PostPosted: Wed Dec 09, 2015 9:59 am    Post subject: Reply with quote

PC Baz beat me too it!!

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Niall996
Imola


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PostPosted: Wed Dec 09, 2015 10:05 am    Post subject: Reply with quote

bazhart wrote:
To try and answer why there are different solutions.

A ball bearing does not benefit from a pressurised oil feed it just needs a supply of fresh cool oil and to be part of a filter system to remove and small pieces of worn metal that inevitably wears off parts slowly. A linear shell bearing does need a pressurised oil supply to keep the shaft metal apart from the shell bearing material as a result of the pressure in the oil between them - without which it could seize.

The sprocket diameter on the end of the shaft runs in an oil bath at up to around 4,500 rpm and the chain fitting round it also travels at up to 40mph in the same oil bath - these between them splash oil in all directions at enormous force and speed and it gets everywhere and is entirely capable of lubricating an open ball bearing nearby.

In fact when the dust seal that Porsche fit has worn slightly and the grease has leaked out - the pressure and force of oil nearby is sufficient to get in and out of that minute seal lip and in most cases can lubricate the bearing sufficiently to last for up to 150K (if it was not damaged too much during the period the grease mixed with wear particles, eventually escaped and the seal lip was worn enough by then to allow oil to seep in again). You can imagine how much better that would be if the whole seal was removed.

The test set up of a bearing rotating in an oil bath does not describe the actual process as the centre of the IMS bearing remains stationary and it is the outside race that rotates. it is true that a rotating disc will throw oil outwards under centripetal acceleration but the gear is many time larger than the bearing running directly in the sump oil bath and the chain running at high speed in the same oil bath throws oil against the crankcase wall where is splashes in ample quantities with much more force and volume that the small IMS bearing does in the opposite direction and so - it is entirely sufficient to lubricate the bearing.

Furthermore that oil bath is a continually cooled source of fresh filtered oil - nothing more needed.

The small bearing itself is just slightly under a spec that would make it reliable for 100% of all fitted with it in this application - so perhaps 99.5% reliable say but with the seal in place that reduces to perhaps 90% or so.

Lots of IMS products are s old as upgrades but in our opinion the only true "upgrade" is to fit the Porsche shaft with the larger bearing or some other modified original IMS that does so. The larger later bearing is man enough for the job but once again benefits from removal of the seal on assembly - which we do during rebuilds.

Baz


Sorry Baz, I'm not technical. Is Alex Yates correct? Hartech's view is that one just removes the 'dust shields' and job done? I could arrange that tomorrow.
 
  
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alex yates
Shanghai
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PostPosted: Wed Dec 09, 2015 10:08 am    Post subject: Reply with quote


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alex yates
Shanghai
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2000 Porsche 996 Carrera 4

PostPosted: Wed Dec 09, 2015 10:13 am    Post subject: Reply with quote

Do not have your bearing removed if it isn't required!!!!!

If the bearing is in situ in the engine, just remove the outer dust shield. Don't have the bearing pulled out unless it's knackered as this can do more harm than good.

It'll also be a damn sight cheaper to just have the outer dust shield removed too.
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bazhart
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PostPosted: Wed Dec 09, 2015 11:09 am    Post subject: Reply with quote

Yes if your bearing was in good condition when you were inspecting it - then just removing the seal would probably enable it to last as well as anything else on the market - but that will not be for ever nor as long as the larger later bearing will last. The problem is to establish what happened to the bearing up until that point. It could have run OK (as most did) and therefore be a good scenario or it could be worn badly (although you can often see this by testing how lose the cage is and the condition of the grease if any is still in there).

Unfortunately removing and refitting a bearing "in-situ" can damage other internals (even with the use of special tools) - it is unlikely but could happen but it could.

However most of these engines will have a slightly shorter life expectancy that many previous Porsche models. Things like cylinder ovality and cracking, head cracks, scored bores and crankshaft bearings etc will not overall last as long as they did on average in say an SC, a 955/968 etc - and like most older Porsches of all types - will require an engine rebuild one day.

So as the incidence of IMS failures is still relatively low (probably little more than some other failures and much lower than cracked, oval or scored cylinders in later models) and if it looks and seems OK - then removing the seal seems a reasonable risk with the proviso that if it did still fail a larger bearing IMS could be fitted while other things are refreshed or even improved upon (depending on who rebuilds it and the specification chosen).

Current prices show just how much older Porsches are valued and so eventually rebuilds will be an acceptable part of ownership for this model range (as it is becoming for other models) and at least things can be improved while doing so.

Unfortunately claims form others that their "upgrade" will last for ever could only be truly comparatively tested by reproducing what happened to the ones that failed - i.e. fit to several hundred cars and run them for thousands of miles with different owners for several years and then assess the outcome - by which time most will have needed an engine rebuild anyway - and the problem could be resolved during it.

Like a lot of problems with these engines the only way to assess the value of specialists contributions is to read and judge their engineering capabilities and compare the various claims and make a judgement on that - perhaps the volume of engines they work on is a factor as well (as you would soon hear about it if they did a lot and had problems).

It is a mine field however. There are specialists that put a good argument on the Internet to encourage potential customers to trust them that are poor engineers that have been involved in failures that others have had to fix afterwards, lost legal cases and had to pay compensation as a result and tried to persuade people that other specialists had done things wrong by lying about the causes of failures elsewhere - relying on running others down rather than presenting their own credentials and arguments supporting their position.

Such is life and such is the business of attracting customers. You will not however see them prepared or confident enough to try and explain technical issues on the Internet nor debate technicalities as some others have.

Unfortunately - it is the small number of weaknesses in this model range that is the root cause of creating a situation that unscrupulous people can exploit (and is what goes on in business everywhere) and because the background reasons were not avoided by the manufacturer they are far more complicated than most would expect and take a lot of experience and research to correct - so in this scenario - there will always be alternative solutions and technical arguments and some owners will get caught out while others will get it right and there are no easy answers - so good luck whatever you decide to do!

Baz
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Niall996
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PostPosted: Wed Dec 09, 2015 11:29 am    Post subject: Reply with quote

alex yates wrote:


Laughing
 
  
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Niall996
Imola


Joined: 07 Nov 2010
Posts: 799
Location: Paris


PostPosted: Wed Dec 09, 2015 11:38 am    Post subject: Reply with quote

bazhart wrote:
Yes if your bearing was in good condition when you were inspecting it - then just removing the seal would probably enable it to last as well as anything else on the market - but that will not be for ever nor as long as the larger later bearing will last.

Baz


Okay. Thanks. I think we all put a lot of trust and reverence in what you say. It's just that I'm a bit pedantic and want to get down to some real core absolutes.

Forget all the other stuff that happens to engines. I'm sure I'll want to rebuild my engine someday to upgrade it or just get it to where it can be. And someday I'll be sending my perfectly good engine to Hartech to get an even better one.

But for now, just on the IMS issue, this is the big one. The one that can be sudden and catastrophic. The back of the mind issue.

What I'm hearing you say, is, assuming that the IMS bearing is fine upon examination, remove dust shields. IF it's for some reason not fine, replace with standard Porsche replacement with dust shield removed. That's it? It's seems like a crazily simple solution after al these years of internet mayhem. And that applies to the 3.4 1998 model specifically which is my particularly area of interest?

Last edited by Niall996 on Wed Dec 09, 2015 11:46 am; edited 1 time in total
 
  
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alex yates
Shanghai
Shanghai


Joined: 06 Mar 2014
Posts: 10406
Location: Lancashire

2000 Porsche 996 Carrera 4

PostPosted: Wed Dec 09, 2015 11:45 am    Post subject: Reply with quote

If you inspect the bearing and it's fine, it'll still be in the engine so you will only have access to the outer side of the bearing - this means you will only be able to remove the outer dust shield. The one on the inside of the shaft can not be removed without removing the bearing.

That's perfectly fine though because all the swilling around of the oil is on the outside face of the bearing.


Do not get you mechanic to start pulling the bearing out just to remove the inner face dust shield.

If the bearing is goosed and needs replacing, Porsche don't do them any more so you will need to source one from someone like SKF to the same spec.
Then pull the dust shields off both sides before fitting. Bearing should only cost between £20 - £50.
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2000 Manual 996 C4 Arctic Silver Convertible

 
  
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