My worst fears

resigner said:

So, I don't go over 3000 rpm until it's warmed up, and keep the oil topped up (uses some, not much, perfectly normal!) but this thread begs the question, what else should I be/not be doing?

Anyone who says avoid this generation of 997 is an idiot in my book. Incredible cars, tiny percentage will have a problem, and as far as value for money goes they are just stupendous.

Are 3.6's really much better than 3.8's? Far far fewer 3.6s out there, so not sure its a fair comparison.......?

Oh, 2007 C2S manual cabrio in case you're wondering. Work from home, doesn't get driven in traffic much at all, and quite often I will go further than I need to so as to warm the car properly, rather than doing the quick trip to Tesco......

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Great your staying under 3k rpm until warmed up, are you running on millers nano 10w50 , the other thing discussed a lot is to fit a LTT which I did , Change the oil every 10k or yearly whichever is first. if its a tip then try to get into the habit of switching from the default 2rd to 1st on the wheel before pulling away. I used to drive mine in manual mode all the time that allowed me to be in the right gear eg 1st to pull away but also going up through the gears you have more control in manual mode as its designed with Eco in mind and will shoot up through the gears as quick as it can which is great for the environment but not so much fun when your driving around the town etc. lol.

I have 68,000 miles now, so only recently went to 5W40 mobile thingy instead of 0W40 at the advice of my indy specialist (Matt at Porschacare). Also do get the oil changed every year.

It's a manual, and even take it easy changing gear until it's all warm.

I also know when the temp needle should start moving by where I am once I leave home depending on route (not to many possible routes!) so keep an eye out for it warming up fast, which is a sign of the oil starting to get low.

cheers

resigner said:

I have 68,000 miles now, so only recently went to 5W40 mobile thingy instead of 0W40 at the advice of my indy specialist (Matt at Porschacare). Also do get the oil changed every year.

It's a manual, and even take it easy changing gear until it's all warm.

I also know when the temp needle should start moving by where I am once I leave home depending on route (not to many possible routes!) so keep an eye out for it warming up fast, which is a sign of the oil starting to get low.

cheers

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Strange that your not running millers nano 10w50 as thats what is the recommended by Hartech oil to use mate. other than that have you fitted a LTT and then your doing everything to minimise any risk :thumb:

Im not going to comment either way but just to say ..

I must work on .. hmm .. 400 ? cars per year that could suffer from this .. i know of a Cayman with bore score .. dam bad as well and a handfull of 997,s and thats in the last 2 - 3 years .

That is also not just me but my garage in total so a lot more cars than just i have worked on .


Maybe in my neck of the woods there arent many issues :dont know:


BTW Phil .. a Range Rover ?? you really must drive a Cayenne sometime and if you can off road .. i have .. awesome !!!

Demort, I will bet that the cars you know of with borescore are running fine ?

Cheers every one for the advice, hoping the next one I get will fine :thumb:

Demort said:

Im not going to comment either way but just to say ..

I must work on .. hmm .. 400 ? cars per year that could suffer from this .. i know of a Cayman with bore score .. dam bad as well and a handfull of 997,s and thats in the last 2 - 3 years .

That is also not just me but my garage in total so a lot more cars than just i have worked on .


Maybe in my neck of the woods there arent many issues :dont know:


BTW Phil .. a Range Rover ?? you really must drive a Cayenne sometime and if you can off road .. i have .. awesome !!!

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Problem is mate the new ones look awesome but the first generation of cayenne was so ugly unless a kit had been added especially to the front end.
But I have to be honest and admit its been considered a few times recently.
was thinking of getting a black one and adding some acid green accents :grin: :grin: :thumb:

Phil 997 said:

Demort said:

Im not going to comment either way but just to say ..

I must work on .. hmm .. 400 ? cars per year that could suffer from this .. i know of a Cayman with bore score .. dam bad as well and a handfull of 997,s and thats in the last 2 - 3 years .

That is also not just me but my garage in total so a lot more cars than just i have worked on .


Maybe in my neck of the woods there arent many issues :dont know:


BTW Phil .. a Range Rover ?? you really must drive a Cayenne sometime and if you can off road .. i have .. awesome !!!

Click to expand...

Problem is mate the new ones look awesome but the first generation of cayenne was so ugly unless a kit had been added especially to the front end.
But I have to be honest and admit its been considered a few times recently.
was thinking of getting a black one and adding some acid green accents :grin: :grin: :thumb:

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Have to say, had a Macan S as a courtesy car from OPC and it was, for a 4*4, bloody good. Not sure how it would fare off road, but it was decently sporty on road! Still, if I needed a 4*4 it would have to be a series 1 or 2 Landie

Just to re-iterate that bore scoring in these engines seems to be a function of

(1) How well the silicon particles are bonded into the cylinder matrix, their size and their distribution (which seems to vary between different cars due to the production process for the cylinder preforms).

(2) The thickness of the oil film between the piston and the cylinder bores (which is a function of the oil grade and the cylinder and oil temperatures on the cylinder wall, ambient conditions, performance of the radiators and the rating of the thermostat).

(3) The bonding between the piston and the plastic coating (that also varies resulting in some well bonded examples just wearing and others f laking or bubbling before a large piece de-bonds and some lasting a very long time).

(4) The running temperatures of the piston (which influences the bonding performance and hardness of the coating and can be a function of the throttle opening and resulting upper cylinder temperatures).

(5) The clearance between the piston and the cylinder (that varies as the open deck cylinder design allows the bores to distort oval).

When a silicon particle becomes free from the cylinder bore it is initially trapped between the piston and the cylinder wall. If it is a big particle it may be bigger than the oil film thickness and rub hard against the bore and the piston coating. The more power being used at that moment - the hotter the piston and the thinner the oil film, and the more the particle will impinge on the cylinder wall and the piston coating before it escapes.

Eventually the particles will penetrate the piston coating and become stuck on the aluminium after which it rubs up and down the cylinder bore dislodging more particles in a downward spiral of cause and effect.

Engines will therefore last longer if the bore happens to have small, well distributed and well bonded silicon particles and well bonded piston coatings (which the owners can do nothing about), if the oil is thicker (as it increases the oil film thickness), if the loads are light (as these influence the squeeze on the oil film and the rate of thickness reduction during each stroke), if the coolant temperature is not too high (as this influences both the oil film thickness under pressure and the piston coating hardness) and if the bores are not too oval and slack (as this influences the rock and knock squeezing the oil film thinner).

The reason bank 2 usually fails first is because the side of the piston that scores (the thrust side) is on the top of bank 2 and the bottom of bank 1. The relatively small amount of coolant feeding the cylinder block flows into the bottom of both cylinders and the temperature increases as it rises up to the top before exiting - so the thrust face of bank 2 pistons is always hotter than bank 1 and the oil film is therefore always thinner on the top of the piston on bank 2 allowing any loose particles to impinge on the piston and bore more often than in bank 1. Also - when resting - the oil will drip down under gravity from the top to the bottom of both banks resulting in the thrust face of the piston in bank 2 being less will lubricated on start up than those on bank 1.

This explanation is also why these failures are not seizures but only scoring on the thrust faces on one side of the bores and pistons.

Boroscopes pick up and exaggerate the running marks and lines seen on the bores. Some have no depth or detriment and are just polishing variations catching the light, some show the result of minor particle scratching but are insignificant to performance or reliability while others show the compound affect of a large silicon particle sticking on the piston and running deeper grooves in the cylinder wall and damaging the piston coating, releasing more silicon particles. How bad this becomes depends upon the point at which that particle eventually escapes.

So the best case scenario is an engine with good but smaller silicon particle distribution and bonding, good piston coating bonding, low running temperatures, good quality relatively thick oil, modest driving styles and regular oil changes.

The worst case scenario is an engine with poor and large silicon distribution and bonding, poor piston coating adhesion, high running temperatures, thin oil, and aggressive impatient driving styles.

I believe that if it were possible to measure and log all those variations from the start of ownership through the car's life until failure it would create a relatively reliable predictive graph of failure mileages. The problem is the impossibility of creating such a log which makes some aspects of contributory factors impossible to monitor and relate to while others can be taken into account by running a LTT, good thicker oil and appropriate driving styles.

These things that owners can influence will not unfortunately prevent the outcome - only delay it because it cannot eradicate the affects of previous owners care, oil and driving styles from influencing the outcome and nothing can be done about the initial condition of the internal components.

This explains why there are such variations in experiences between very early failures and very long survival.

Fortunately most last a perfectly acceptable length of time and there are still only a small proportion failing - and thankfully when the failures do occur you can usually still drive the car for a long time until the wear is so bad a repair is essential.

Finally it is very important to realise that interpreting the visual pictures from a boroscope is not easy and demands a lot of experience - as many that have been assumed are bad scoring are just running marks of no consequence while others do indicate a serious scoring. Also the very small number of failures in the 9A1 Gen 2 engines are completely different complete seizures on both sides of the piston and bore is any bank and usually need fixing immediately after they fail - making the Cayman S, 996 and 997 Gen 1 failures more manageable.

Baz

bazhart said:

Boroscopes pick up and exaggerate the running marks and lines seen on the bores. Some have no depth or detriment and are just polishing variations catching the light, some show the result of minor particle scratching but are insignificant to performance or reliability while others show the compound affect of a large silicon particle sticking on the piston and running deeper grooves in the cylinder wall and damaging the piston coating, releasing more silicon particles. How bad this becomes depends upon the point at which that particle eventually escapes.

Finally it is very important to realise that interpreting the visual pictures from a boroscope is not easy and demands a lot of experience - as many that have been assumed are bad scoring are just running marks of no consequence while others do indicate a serious scoring. Also the very small number of failures in the 9A1 Gen 2 engines are completely different complete seizures on both sides of the piston and bore is any bank and usually need fixing immediately after they fail - making the Cayman S, 996 and 997 Gen 1 failures more manageable.

Baz

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I think this is now the biggest issue. It's too easy for some garages to see marks with a borosocpe and say 'engine rebuild required' when in fact there is not actually an issue, or that the engine will still perform perfectly for many thousands of miles before any symptoms appear or a rebuild is actually required, if ever.

My engine had light scoring visible by boroscope at 32k miles. When my engine failed at at 50k miles due to IMS bearing failure :evil: (I was waiting till clutch needed changing before replacing the bearing :frustrated: ) When my engine was opened up the scoring was not really an issue and probably not become one for 50k+ miles if ever. There was a couple of very small scratches on the plastic coating on two of the pistons (but the coating still fully intact). I guess now from Baz's description the small scratches were caused by a silicone particle coming loose from the cylinder wall. However as my engine was apart I decided to go 'all in' and have 6 new Hartech liners fitted with 3.9 Forged pistons.

I had my rebuilt Nikasil lined engine boroscoped after the 1000 mile run in and it has visible running in marks on the cylinders which to the untrained eye could be classed as scored bores! The difference being the running in marks are the full length of the cylinder and in various places around the cylinder, (not just concentrated on the thrust face). You can also still see the honing marks in the lines.

Demort said:

Im not going to comment either way but just to say ..

I must work on .. hmm .. 400 ? cars per year that could suffer from this .. i know of a Cayman with bore score .. dam bad as well and a handfull of 997,s and thats in the last 2 - 3 years .

That is also not just me but my garage in total so a lot more cars than just i have worked on .


Maybe in my neck of the woods there arent many issues :dont know:


BTW Phil .. a Range Rover ?? you really must drive a Cayenne sometime and if you can off road .. i have .. awesome !!!

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Thats a reassuring summary Demort and you have a much better perspective than most so worth take note

With regards to the Cayenne even the old ones are suprisingly capable off road with decent tyres - i speak from experience as i had an old Trooper stuck in the Sea once (long story) with the tide upto the dashboard and Cayenne came to our rescue pulling us out in loose sand !

Fortunately most last a perfectly acceptable length of time and there are still only a small proportion failing - and thankfully when the failures do occur you can usually still drive the car for a long time until the wear is so bad a repair is essential.

Finally it is very important to realise that interpreting the visual pictures from a boroscope is not easy and demands a lot of experience - as many that have been assumed are bad scoring are just running marks of no consequence while others do indicate a serious scoring. Also the very small number of failures in the 9A1 Gen 2 engines are completely different complete seizures on both sides of the piston and bore is any bank and usually need fixing immediately after they fail - making the Cayman S, 996 and 997 Gen 1 failures more manageable.

Baz[/quote]

Hi baz, yes i also agree with this 100 per cent and the only people worthy of doing a good inspection are those with experience