Hi Mike, Cylinders 4 & 5 both seized on one side of the piston - classic usually of too much piston clearance caused by - the usual cylinder ovality.

Same scenario as previous 996's - liner too thin and unstable for the power output - gradually going oval and the resulting increased piston clearance allowing blow by that burns the oil on the piston and overheats the friction surface.

I must admit that I still don't know as much as I would like about the nature of the instability of what are generally classified as metal matrix composites (like the Lokasil liner) - but I know that creep under load/heat etc is a general problem. I think it is caused by the fact that the particles are bonded together at a small interface area which slightly shifts position and re-sets itself? The movement is minute in each particle bud added up together results in a shift in shape or size taking up a permanent "set" under heat and load.

Also Lokasil is not like metal, much more porous (which provides a good lubricating surface ideal for cylinders) but strengthwise it is more like comparing an aero bar with a solid chocolate bar - when squeezed it compresses easily to a much smaller size and it fails more suddenly under load.

I think the interface between the Lokasil preform and the outer cast alloy jacket must also vary between castings as we have seen a lot of evidence of some areas where the two materials joint face being very well bonded together while in other areas there is hardly any bonding - perhaps even minute voids.

I would guess that too great a temperature gradient (driving fast too soon from cold) would increase the "creep" effect and so for the many good reasons for ensuring the engine is well and truly warmed up before blasting it - you can add the probably life of the liner/piston and of course the avoidance of a cylinder head crack (although we havn't come across that on a 997 yet).

What problems with this engine have you (and others) come across so far?

Baz

Hi Mike, it was only a short while ago when I suggested that I knew of no reason why these 997 engines would not have similar failure rates to the 996's - following which others (who obviously know better than me!) poo poo'd that anticipating or stating that they would obviously be more reliable as Porsche will have solved some of the problems.

Just like the 996's early on - it takes some years and miles before the few failures in the mix of generally reliable engines - surface - and I think we are seeing the beginning of that - and although the 997's are very quick and a delight to drive and generally reliable - the extra torque transmitted through essentially the same engines (which increases the loads and heat generated) - may well even shorten the mileage before the few more fragile examples fail. Indeed the evidence so far is that those that are failing are doing so at much lower mileages than the 996's started failing at.

Once again customers on our Maintenance Plan need not overly worry as we already have the liners in manufacture to repair the crankcases and the security rings to prevent future failures and reduce the ovality that may have already occurred - plus the other usual mods to improve the engine overall - and this costs them very little if they are on the scheme (paying only for parts). Even if they are not on the scheme - costs are still sigificantly lower than a new or risky used engine.

Looks like we are all going to be mighty busy as more older cars age another year, increase their own mileages and more of them fail, while newer examples probably start failing earlier and piling on the numbers. That's why we have just increased the range of engines we can fix and trebled our capacity, space, equipment and staffing to cope with what we see as an exponantial increase in business ahead.

There is also evidence of some other businesses trying to get in on the engine rebuilding act (such is the nature of a free market opportunity) but so far we had had to pick up the pieces of several diabolical failures and jobs they could not complete or eventually over charged for (have you come accross this yet?).

While you, we (and similar respected Porsche specialists) know those competitors we can trust and those we cannot - these new businesses are largely unknown to me and a real danger to a member of the public in trouble seeking an easy and apparently inexpensive local solution that may backfire big style.

So I hope the public will be careful when chosing their preferred repairer to assess their background and success rate before taking a risk they may later regret.

Baz

Here comes the vulture...

I don't think anyone owes you any 'withdrawn remarks' - it is not your thread, never was, but you just came along in your usual patronising way and exploited it to try and remove that massive Porsche-sized chip off of your shoulder...

Get over it mate - you couldn't buy one on your terms, so presumably you are now driving something else? Just enjoy it and butt out of the Porsche threads please - permanently: They exist for those that are enthusiastic about the marque - not as a forum for you to vent your spleen because you couldn't get a massive discount when you tried to buy one (that you presumably couldn't really afford) years ago.

Baz, am I right in thinking these are further suspected 'fatigue failures'? In other words, a consequence of not warming engines up properly before giving them the beans? This makes sense to me, as you have a jacket of very cold water around the heads and bores, until that warms up properly, there will be a massive thermal difference across the metal thickness - ultimately resulting in the fatigue cracks we know about. Air (or should that be oil) cooled engines are not affected by this as 'sprayed' oil will not have the same cooling effect as a relatively static body of cold water, so you don't get the same temperature differential across the metal thickness.

This would also help to explain why Turbo engines are not really affected by this... I believe I'm right in saying that only the heads are cooled on the Turbo (and the bore liners are much thicker as well?)

Do you know bcnrml - I am never really sure where you are coming from - and am only aware of a lot of arguments and disparaging comments about you from others over the years and lots of in fighting etc the details of which I paid little attention to . Frankly I am not interested in such battles and am not sure in which way you think I owe you an apology (anyway thanks for letting it drop if I do - sorry) except I always say what I think and have always been consistent and am one of the few people on here that know what they are talking about technically and I have only ever tried to report that and wherever possible keep out of any resulting politics - except where views go against the clear engineering evidence.

However - if you would allow me to be a little philosophical and serious - as I have aged - I increasingly realise that people have very different views of the World - their own individual reality - which they cling to like their life depended on it and on them being right and attack and fight against anyone with a different viewpoint that might destroy the image they rely upon to confidently run their lives. From this almost all the wars and religious bigotry have emerged.

This - in turn - is a problem of how to explain something in a way that most people can accept - when simply reporting it often falls on so many deaf ears and therefore becomes a waste of time and doesn't achieve its objective.

So while the technical evidence grows and firms up, the causes, consequences, frequency etc are a matter of opinion and while the engineering consequences are irrefutable for those that have failed - opinions about what that technical evidence means for those that are still running will always be a matter of an individuals view of the World and different for everyone. So I accept that whatever I find as a cold hard fact of life as an engineer - the way people interpret the implications will always vary greatly and this creates a huge problem in conveying that technical information to all the readers whose "Porsche World" is so different for each of them.

Furthermore - I am not claivoyant - and it is difficult and dangerous to make firm predictions about things when the sample is so small. However - although my sampling of failures is probably the highest in numbers - it is small compared to the numbers in existence - but we both know small sampling is statistically very reliable indeed - but others may not have such confidence. So even though I suppose my technical interpretation and engineering experience - is amongst the best available - you will find lesser engineers disputing it vehemently).

This gives me huge problems in trying to convey what I know to be true technically with what I imagine may happen in the future to people all with different ways of interpreting the information and all with different axes to grind.

Another problem is that people simply are not rational and broad minded. If I made a statement like - "most 996's will eventually crack a liner or seize the engine as a result of metal matrix cylinder creep" someone will post in to claim a 300,000 mile engine that is still running - totally ignoring the hundreds that have failed below 50K and as if all the cracked engines we have relined as a result didn't actually happen. People seem unable to divorce something they have heard or read about just one example from a general balanced view of averages and then fight their corner as if their World depended on them being right.

Then there are vested interests from the manufacturers, people who rely on selling the product and don't want to read about potential problems - people with different aswers trying to get a piece of the action - possibly all missinformed or lying to protect their interests and potential litigation if you are unfortunate enough to cross the line in your critisim - even though you may be right (and the law is not fair or equal and will always favour those with the biggest budgets - and therefore not me).

I have over the years found lots of engineering weak spots (many of which I feel would be too difficult to open up to public debate and scrutiny and keep to myself), but when I have made public predictions about the consequences - usually it results in being told by the majority that I am wrong initially, then later on when it is clear I was right that they can fix it better than me and eventually the original discovery (now being generally accepted) being claimed by everyone else and not me - such - it seems - is life. Even though I honestly cannot remember any published engineering prediction of mine being eventually proven wrong nor any of my technical explanations being proven wrong - still each time I enter a new example for public scrutiny - the same doubters - for all their various individual reasons will criticise the discovery - leaving the public not knowing who to believe and unable to benefit - which is a great shame.

So to counter all these problems and still try to convey warnings, give advice to help people avoid problems or fix them for as little cost as possible - I find that the best way is to be cautious how I approach conveying the information, respond to the feedback and change how I continue and try to reach as many people as possible to help them out of an often desperate financial problem caused by basically inadequate engineering and poor customer support.

Ironically though I genuinely believe that these are great cars and that Porsche had to change their philosophy and manufacturing methods to survive, that their warranty is a good option if you can afford it while they are relativley new and that many similar sports cars have similar or worse failings. It seems that the biggest let down is simply that the reputation for the quality of the previous engineering (when it was so good Porsche were often "going bust" and were unable to modernise) is greater than that of the new product they then sold with the same customer expectations.

So in conclusion they are great cars - IMHO statistically acceptably reliable for the price and performance (although not as reliable as previous models) - with weak spots that only affect a small number (but with huge potential consequential costs for those that do fail) and there are a few businesses like ours that can offer a reasonably priced solution or an optional protection through a Maintenance Plan - if a failure occurs.

Meanwhile in attempting to convey those technical realities to a "moving target audience" and having to duck and dive a bit - simply to get the message over to the majority - whose reaction is often different to what I may expect - please be patient if at times my comments vary from mild to strong - as I will simply be trying to tread the best course to convey the true reality to as many owners as possible while avoiding potential pit falls coming back at me.

I know the above sounds very arrogant and I am genuinely sensitive about that - but I am one of the best engineers that has proven himself in the design and manufacture of racing engines, aerospace engineering, composite design and more recently Porsche service provision. I have owned two businesses (one sold to a plc) and have been a director of three public companies and have as a result seen and been exposed to a lot of the World of engineering and people and continually proven my capabilities.

Throughout my career I have been both ethical and honest but these Boxster, 996 and 997 engines have the potential to severely harm the financial resources of enthusiasts and I am merely trying to provide good engineering advice and solutions to help them - and in so doing I admit that I hope to benefit myself and my business through entirely legitimate and valuable services and products - that also benefit unfortunate owners - and see nothing whatever wrong in that.

However business success has never been a problem to me, we have always been busy and always made a profit and my main aim in offering my opinions is to give good advice to those that may well benefit from it one day and to protect them from rogues by empowering them with the right knowledge and good advice.

Sorry this has been so long winded - I felt it was important.


Baz

Sorry- what an idiot - the photos are on pcgb web site under 16 valve 3 litre turbo about 10 days ago.

Baz

BCNRML... Just for the record, my problem with you is not so much in the content of any of your posts, but it is the arrogant and patronising nature of your delivery. Oh, and the fact that you only ever post when there is an opportunity to have a pop at Porsche - a quick scan of your posting history shows very clearly the great delight you take in reporting on poor financial results or more engine failures.

We all know that a percentage of Porsche engines will fail prematurely (I still happen to believe that the premature bit is mostly due to user abuse and the science appears to agree with that view as well): However, many of us enjoy our 911s and look after them mechanically to try to prevent this happening, whereas you seem to enjoy gloating about other people's misfortune as it is another nail in Porsche's coffin as far as you are concerned...

Now, if you were to be open and honest about your agenda and interest in this subject, and adopted a more balanced view than simply criticism, then just maybe your critics might stop being "potty mouthed" about you - unless of course it turns out your agenda is some bitter and twisted revenge behaviour, which, quite frankly, is all it appears to me thus far.

So, if you would like a bit more respect from everyone on here, how about stopping behaving like a Troll and being a little less patronising (not everyone else on PH is the idiot that you seem to think we all are) and maybe explaining your history with Porsche and your reasons for posting?

I won't hold my breath...

Interestingly, a site that offers a similar service to Baz in the USA claim that cars that are tracked regularly are much less likely to fail prematurely... so maybe there is some truth in this idea of work-hardening?

I don't know how my early (3.4) C4 was used before I bought it, but in my hands it was used pretty much every day and mostly for journeys over an hour in duration (so all materials fully up to temperature throughout). I went from 42,000 to 110,000 without it even needing an oil top-up between services right up to when I sold it...

On the American website they actually say...

I don't think the alloy is "work hardening" as it is not subjected to rapid stress reversals because the inner Lokasil preform is stiff and only moves slowly over a long period of time - rather than moving a lot and effectively metal fatiguing - but look there is plenty of evidence of similar problems when other manufacturers over the years have bored out a basic block casting to increase capacity and turned a previously reliable engine into a relatively less reliable one and creep is a known but not fully understood problem with composite constructions.

The 996 was the original 3.2 Boxster S block casting bored out bigger - but with an added disadvantage that half the liner thickness is Lokasil and half Crankcase alloy and so the alloy biut is proportionally much thinner than the 3.2, 2.7 or 2.5 Boxster variants.

I have previously described the Lokasil preform being like ball bearings suspended in a glue/resin to lock them together - and I think it is a valid analogy. As I understand it - under stress and heat the point of contact between the balls allows minute movement over time at the glue interface (because with heat the bonding is less strong and the load/unit area higher than a homogeneous construction) and the balls roll slightly in the direction of stress - resulting in a small but permanent deformation or movement.

Effectively - over time the liner does not resist the continual load from the piston pushing on the bore to rotate the crankshaft and the outer alloy is too thin to hold back the gradual ovality that results.

All the bores get bigger in the direction of the piston thrust load but smaller in the opposite side to side direction 180 degrees from that thrust face and this can only be explained by creep which composites are known to suffer from in similar circumstances.

Work hardening comes about when the chrystalised structure of the material changes through loads but the Lokasil silicon surface material is still just as good becuase once we have re-rounded those oval bores that have not yet cracked and fitted restaining rings to hold them in that shape and prevent further movement - they continue to work perfectly again - providing more bottom end punch and crispness than before due to the now improved (or more accurstely reduced) piston clearance and better ring sealing.

It seems that the gradual change of shape of the Lokasil preform imposes a stress on the thin outer alloy until it exceeds its elastic limit - which seems to be shortly after the ovality can be measured at 10 to 12 thou (or 0.25mm to 0.3mm). Alloy castings are generally rigid but crack at fairly low strain extensions compared to say Dural (which is extruded) so that fits with our experiences as well and those that have distorted that much but not yet cracked work perfectly well again once we have forced them back into shape again and held them there.

Simply making the outer casting thicker or fitting support rings during manufacture would have prevented the alloy reaching its elastic limit and therefore kept it in shape without cracking.


Baz

Simply because this is a public web site - potential future and existing customers provide the livelyhood of both myself and all my staff - and so I am bound to react if anyone suggests anything disparaging about the services we provide and the attitudes we work with.

Because this is my livelyhood, I am bound to consider the fact that others reading these threads may not have previously worked out where you come from or reside - so when you state that you go to Germany because you can get good service at reasonable prices from people who take a pride in their work - and cannot get this elsewhere you implied that this was not possible in the uk and therefore the way you expressed your preference suggested that I (amongst others) do not provide that level of service here - which I do and so I was offended by that implication. Some readers may even imagine that you go from the UK to Germany as the only way to get the service you seek - I often think you (and other readers) would benefit from thinking more broadly about the implications of your posts first rather than launching in with such a potentially critical manner all the time - unless you actually enjoy controversy for its own sake for some reason!

Even I who have been involved with various bits of correspondence with you didn't know exactly where you reside (and if you were honest you must admit that you like your details remaining private AND DEFEND YOUR RIGHT TO DO SO) and if I lived permanently in Spain I think I would also drive to Germany for my service work - as I too have always found their approach to services and repairs very typically Teutonic, pragmatic and dedicated - so now I understand where you live - it all makes more sense to me and is not so contentious or critical. But you must realise that not every reader has worked out where you come from or reads all the previous posts and that my business is important to me and the other shareholders and we rely upon - amongst other things - the comments people make about us to establish our reputation when hoping to benefit from new business in our area and anyone reading your comments as they were expressed may not actually realise the facts as I now do myself.

If you had said that you go to Germany because you live in Spain and also get the good service they provide there - I would have not had any axe to grind.

By the way I actually do have quite a few customers with new cars and they prefer our approach and direct contact with the people that do the work and our responsible and conscientious ethics and reasonable prices and get their first services and future repairs done here.

If you are ever likely to be in the Alicante/Torrevieja area - and if you would like to meet up then let me know beforehand by E-mail at Hartech - as I visit frequently and it would be interesting to meet face to face.

Baz

Chaps, you all seem very intelligent and dedicated to improving and enjoying the brand but it does seem to be a lot of wasted energy sounding off against each other.
I like reading this thread (engineering wise) because I really need to scratch the 'Porker itch and it's interesting but I'm afraid the intellectual sounding off is probably getting a little tiring. Dueling swords away for now hey??

Hartech, when I do finally get a Porsche I will most definitely be visiting your good-self for chat about servicing, engineering and general care.