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100K miles. Is yours above or below?

Loving this thread still.. There's a lad on Boxa.net who has just found a coppery glittery sludge in his oil filter on 110k miles (986s). He had a tapping noise for the past week or two which sounds to me like the big end shells being worn.

Obviously he's gutted but from an objective standpoint it is very interesting to see the modes of failure on these engines now we are past the IMS worries of the M96 <3.6 units.

I (may have mentioned this earlier) sent my oil off to the millers lab for my boxster and it came back with no sign of wear whatsoever, so I'm continuing with my 5k mile service intervals with an oil analysis every other service.
 
I make a contribution to this post with some trepidation that it will be misunderstood – but it is important for owners to recognise and accept that there are many influences on engine life that are outside of their control and may result in an early failure, a very long life or – for most – an 'average expectancy". This means that while there will be reports that many engines have covered huge mileages there are also others that never managed to get past 20K – the why's and wherefores are difficult to quantify or provide reliable correlations for or generalised advice.

What is for sure is that there are more 'weaker areas" than some older Porsche models and that means that the car's previous use (before the present owner) will have more of an influence of life expectancy as will the general quality of some of the original build and components.

Although older models were almost bullet proof, cars that have been respected with owners with mechanical sympathy who always warmed up their cars properly and had good quality maintenance carried out and then were driven reasonably within legal limits, will on average last much longer than those whose first owners thrashed them from cold knowing they would not be the owners when the consequences materialised (or who afforded the Porsche warranty – so were not too bothered about long term consequences anyway).

The difference in engine loads, wear rates and thermal stresses magnify exponentially with throttle opening, revs and top speeds – so unless you know for sure the total driver history including the driver's attitudes from new – it is impossible to assess the likely lifespan.

With the crankshaft (in common with most recent engine designs from all manufacturers) having thinner bearings (between 57% and 70% of the 944 size for example) and the crankshaft only 1/3 as stiff – and with the flywheel overhanging by 3 times the length - much more wear on the bearings will result – 'IF" the car has been driven really hard – especially from new. Because of the older models 'over engineering" the magnifying affect of hard driving was not so relevant – but although these newer engines driven with respect will still last a very long time but those driven very aggressively will not.

The thrust loads on the cylinders (earlier 3.4 engines) and the wear on piston coatings (later models) all increase exponentially with revs and throttle opening leading to premature cylinder cracking or bore scoring while the temperature gradients inside the engine react with increased stresses on a lot of components.

If an engine is over engineered it can stand the stresses of aggressive driving much longer than one designed to a finer tolerance level – so it is not unusual with more modern engines for there to be some with short lives and some with very long lives and the only advice experienced experts can provide is the 'average" they work with. This is in itself flawed because they tend to only see the engines that have so far failed and therefore their experience is focussed on a relatively small and select group. It is most likely however that those they do repair had experienced a harder life than those that survive longer.

The IMS bearing was probably one of the few areas that this reality did not apply to – being much more random – but it is not a common failure and the higher the mileage it has survived the less likely it is to fail – making the most common failure now being 3.8 bore scoring. However neither bore scoring nor even cracked cylinders in earlier models are too catastrophic and rarely wreck the engine – usually making a post failure rebuild viable.

In contrast the crankshaft bearings are critical because if they wear prematurely the result can wreck the entire engine.

As engines wear the clearances between the crankshaft bearings and the piston to bore increase while piston coatings reduce and the hard silicon cylinder particle loss increases – so in both cases changing to a thicker oil viscosity helps prolong lifespan. Cars used lightly may very well still cover very high mileages on the original oils but those driven more spiritedly will benefit from an oil upgrade and the sooner that was done the longer they are likely to last. Similarly the fitting of a LTT, cleaning radiator blockages etc all prolong potential lifespans.

If at any time in the car's life - it suffered a failed coolant pump, blocked or leaking radiator, hose or header tank, failed radiator fan, low coolant, low oil level, extended oil change period etc – that all eventually influences long term life expectancy.

Owners buying older cars (on average and I accept there are always exceptions) tend not to abuse them as much as some previous owners and often do all the right things to preserve their car but this cannot completely repair damage and wear that has already taken place.

This all means that if you are not sure about repair history, previous owners care or driving style - your engine could be nearing the point at which the crankshaft, or cylinders may fail and if you intend to keep the car it could cost you less to have a rebuild at the right time than risk a more serious failure - providing a reliable car for your enjoyment and benefitting re-sale values as they appreciate with time.

Since this post has been about 100K cars – can I respectfully advise that despite the reported exceptions - this is a mileage at which the average will have worn crankshaft bearings, oval cylinder bores, piston coating loss and yet can still be rebuilt to a reliable standard at moderate costs and result in a brilliant car to own and drive. Around and over this mileage we are beginning to experience serious failures and the need to replace expensive parts that would have been Ok if rebuilt slightly earlier.

My concern is that too much confidence generated because some cars have managed to cover high mileages may result in more owners pushing their boundary of expectations towards higher rebuild costs for those that leave their own engine too long before rebuilding it.

Like all risk assessment it is impossible to be sure of the outcome until failures occur but also like all good and reliable preventative maintenance – averages and experience provide the best guide to the right mileages to act. Lower oil pressures on tickover, increased oil consumption and reduced performance can all help but ultimately you always have 2 choices, rebuild before failure or afterwards and at over 100K – my advice is to seriously consider a reliable pre-emptive rebuild that also improves the mechanical specification from the original.

These fantastic cars still look and drive brilliantly after nearly 20 years (and are usually in better overall condition than the older examples) so there is no reason not to expect them to eventually enjoy the appreciation in values that help justify engine work (and other contributors are quite right to point out that even the older cars had various issues needing engine attention eventually) it will just be better with this model range to get it done earlier rather than later.

Can I also add that this advice is not in any way going to increase our business turnover or profitability. We are flat out all the time rebuilding engines that have failed and those that have more serious failures cost more to fix and actually increase our turnover and labour content. With all existing M96/7 cars covering ever increasing mileages the numbers needing repair will continue to rise and with oversized engines coming on line, increased numbers of competition engine rebuilds being requested (as a result of our continued success on track) and developments under test for 9A1 (Gen 2) engines – we are already at maximum capacity with no desire to expand any further.

But we make our living from Porsche cars and prefer for our customers to still hold the marquee in the same awe as we do for fantastic engineering of superb cars that look and perform brilliantly at ages and mileages that most other sports cars have been scrapped at and to provide a service that benefits them by rebuilding for the long term at the right time rather than be involved in a complete disaster that destroys confidence and ultimately damages reputations.

Over to you - I'm off to the bomb shelter!


Baz
 
Great info as ever :D

However I think it would cost more for a pre emptive Hartech rebuild than I paid for the whole car. :floor:

My fingers are crossed for a popopbangbang style reliability, that the previous owners had some mechanical sympathy.

But if its value does skyrocket, then I might consider it. :thumbs:
 
A great insight into the common wear areas at 100k miles. Many thanks for the contribution Baz.

As I approach 100K, I have a decision to make. Do I keep and have some relatively affordable pre-emptive repair work carried out before damage to the crank etc. (as some others have commented in this thread, and take it as an opportunity to upgrade) or do I sell on as is and leave such work for the next owner. The market has 'priced in' a degree of such work as 911 prices reduce progressively up to an through 100k miles.

I have had my car approx. 9 years now, so ready for a change.
 
Any used engine is a gamble, especially one which has done its likely "design life" of 100k miles or 10 years.

However I am gambling that my engine is one of the good ones, good for 300k :D

Unless I see sparkly copper in the oil, or it stops one day it is not getting rebuilt.

If it explodes, my car is now worth the same as a roller than I paid for it, so no big deal.

So unless it magically "rises in value" by the cost of a rebuild, I would find it hard to justify given it might be completely unnecessary.
 
My feelings are similar to Wasz's as I don't have a spare +/- £10k for an engine rebuild (may come to more as there are several worthwhile things to do whilst the engine is out).

If it started to play up, make noises or go bang I'd have to decide if it's worth repairing, in my mind I accept £1000 a year depreciation and so over 3 years it's 'depreciated' £3k on an £11k purchase, if I kept it running for another 3 years and then sell it for £5k as a rolling chassis it's paid for itself (ignoring maintenance).

The fact that it's probably gone up £2k despite adding 20,000m and is now almost 100,000m is a bonus and offsets the running cost. It's given me loads of smiles during my ownership so I will just focus on the good times if it's not worth repairing.
I've done up a car in the past and then someone crashed into it and wrote it off, the insurer would not pay out to cover the upgrades so that was money lost.
 
It would be useful to know what clues to look for so one could prepare for an engine rebuild, as much as I'd hate for my engine to fail I'd also hate to spend a small fortune on a rebuild to find that on disassembly that it was actually in really good condition and could have happily gone on for another 50,000m+ trouble free.

So we should keep an eye on:
Low oil pressure at tick over
Unusual noises, knocking = bore score
Change the oil every 6000m & inspect the oil filter
Get an oil sample test every 12,000m to see if the copper levels from the main bearing shell wear is increasing and give an indication of other component wear.
I now assume my car has good IMSB so I've finally given up worrying about that.

Also:
Warm the car up before a blast & cool down after
Fit a LTT & keep the cooling system in tip top condition
Avoid prolonged and regular congested city driving

There's probably several other helpful hints but the above is not expensive and will hopefully reduce wear to that less than an 'average' car.

No one wants a money pit but gearboxes, suspension, electronics, stereos etc can all fail and cost lots or you may well crash or be crashed into which could also ruin your day.

Having said all the above I'd love to have a bigger bore Hartech rebuild if I had the readies!
 
Great post Baz, thanks for the contribution. What you've said makes perfect sense.

My attitude is that I'll over service it and will send some oil off for analysis every other change. As soon as I notice the metal contents rising (theres many more tested than just copper) I will start to seriously think about what to do with the engine.

One thing I will do (as advised by your post) is change the oil next time to a thicker/heavier one.

Thanks again Baz!

:thumb:
 
bazhart said:
I make a contribution to this post with some trepidation that it will be misunderstood – but it is important for owners to recognise and accept that there are many influences on engine life that are outside of their control and may result in an early failure, a very long life or – for most – an 'average expectancy". This means that while there will be reports that many engines have covered huge mileages there are also others that never managed to get past 20K – the why's and wherefores are difficult to quantify or provide reliable correlations for or generalised advice.

What is for sure is that there are more 'weaker areas" than some older Porsche models and that means that the car's previous use (before the present owner) will have more of an influence of life expectancy as will the general quality of some of the original build and components.

Although older models were almost bullet proof, cars that have been respected with owners with mechanical sympathy who always warmed up their cars properly and had good quality maintenance carried out and then were driven reasonably within legal limits, will on average last much longer than those whose first owners thrashed them from cold knowing they would not be the owners when the consequences materialised (or who afforded the Porsche warranty – so were not too bothered about long term consequences anyway).

The difference in engine loads, wear rates and thermal stresses magnify exponentially with throttle opening, revs and top speeds – so unless you know for sure the total driver history including the driver's attitudes from new – it is impossible to assess the likely lifespan.

With the crankshaft (in common with most recent engine designs from all manufacturers) having thinner bearings (between 57% and 70% of the 944 size for example) and the crankshaft only 1/3 as stiff – and with the flywheel overhanging by 3 times the length - much more wear on the bearings will result – 'IF" the car has been driven really hard – especially from new. Because of the older models 'over engineering" the magnifying affect of hard driving was not so relevant – but although these newer engines driven with respect will still last a very long time but those driven very aggressively will not.

The thrust loads on the cylinders (earlier 3.4 engines) and the wear on piston coatings (later models) all increase exponentially with revs and throttle opening leading to premature cylinder cracking or bore scoring while the temperature gradients inside the engine react with increased stresses on a lot of components.

If an engine is over engineered it can stand the stresses of aggressive driving much longer than one designed to a finer tolerance level – so it is not unusual with more modern engines for there to be some with short lives and some with very long lives and the only advice experienced experts can provide is the 'average" they work with. This is in itself flawed because they tend to only see the engines that have so far failed and therefore their experience is focussed on a relatively small and select group. It is most likely however that those they do repair had experienced a harder life than those that survive longer.

The IMS bearing was probably one of the few areas that this reality did not apply to – being much more random – but it is not a common failure and the higher the mileage it has survived the less likely it is to fail – making the most common failure now being 3.8 bore scoring. However neither bore scoring nor even cracked cylinders in earlier models are too catastrophic and rarely wreck the engine – usually making a post failure rebuild viable.

In contrast the crankshaft bearings are critical because if they wear prematurely the result can wreck the entire engine.

As engines wear the clearances between the crankshaft bearings and the piston to bore increase while piston coatings reduce and the hard silicon cylinder particle loss increases – so in both cases changing to a thicker oil viscosity helps prolong lifespan. Cars used lightly may very well still cover very high mileages on the original oils but those driven more spiritedly will benefit from an oil upgrade and the sooner that was done the longer they are likely to last. Similarly the fitting of a LTT, cleaning radiator blockages etc all prolong potential lifespans.

If at any time in the car's life - it suffered a failed coolant pump, blocked or leaking radiator, hose or header tank, failed radiator fan, low coolant, low oil level, extended oil change period etc – that all eventually influences long term life expectancy.

Owners buying older cars (on average and I accept there are always exceptions) tend not to abuse them as much as some previous owners and often do all the right things to preserve their car but this cannot completely repair damage and wear that has already taken place.

This all means that if you are not sure about repair history, previous owners care or driving style - your engine could be nearing the point at which the crankshaft, or cylinders may fail and if you intend to keep the car it could cost you less to have a rebuild at the right time than risk a more serious failure - providing a reliable car for your enjoyment and benefitting re-sale values as they appreciate with time.

Since this post has been about 100K cars – can I respectfully advise that despite the reported exceptions - this is a mileage at which the average will have worn crankshaft bearings, oval cylinder bores, piston coating loss and yet can still be rebuilt to a reliable standard at moderate costs and result in a brilliant car to own and drive. Around and over this mileage we are beginning to experience serious failures and the need to replace expensive parts that would have been Ok if rebuilt slightly earlier.

My concern is that too much confidence generated because some cars have managed to cover high mileages may result in more owners pushing their boundary of expectations towards higher rebuild costs for those that leave their own engine too long before rebuilding it.

Like all risk assessment it is impossible to be sure of the outcome until failures occur but also like all good and reliable preventative maintenance – averages and experience provide the best guide to the right mileages to act. Lower oil pressures on tickover, increased oil consumption and reduced performance can all help but ultimately you always have 2 choices, rebuild before failure or afterwards and at over 100K – my advice is to seriously consider a reliable pre-emptive rebuild that also improves the mechanical specification from the original.

These fantastic cars still look and drive brilliantly after nearly 20 years (and are usually in better overall condition than the older examples) so there is no reason not to expect them to eventually enjoy the appreciation in values that help justify engine work (and other contributors are quite right to point out that even the older cars had various issues needing engine attention eventually) it will just be better with this model range to get it done earlier rather than later.

Can I also add that this advice is not in any way going to increase our business turnover or profitability. We are flat out all the time rebuilding engines that have failed and those that have more serious failures cost more to fix and actually increase our turnover and labour content. With all existing M96/7 cars covering ever increasing mileages the numbers needing repair will continue to rise and with oversized engines coming on line, increased numbers of competition engine rebuilds being requested (as a result of our continued success on track) and developments under test for 9A1 (Gen 2) engines – we are already at maximum capacity with no desire to expand any further.

But we make our living from Porsche cars and prefer for our customers to still hold the marquee in the same awe as we do for fantastic engineering of superb cars that look and perform brilliantly at ages and mileages that most other sports cars have been scrapped at and to provide a service that benefits them by rebuilding for the long term at the right time rather than be involved in a complete disaster that destroys confidence and ultimately damages reputations.

Over to you - I'm off to the bomb shelter!


Baz
Your ethos - our respect
 
Peeping over the parapet – of course if an owner could not afford a rebuild (and would have to accept scrapping the car if the engine blew) there is no choice to make and similarly if an owner could easily afford a rebuild even if the engine exploded through leaving it too late – they could decide to wait and see what happens. However I guess most owners of M96/7 cars (now 10 to 20 years old) intend to keep them and look after them and many will be approaching 100K.

When there are signs that components are getting worn out, worn down, perished or not performing properly - very few people would continue driving until their brakes failed, hoses split, tyres burst etc – but they can more easily be assessed – but engines – in contrast – cannot – except that is when you have seen inside and rebuilt hundreds for over a decade when you do begin to be able to predict quite accurately where they are up to and when it is best overall to consider a rebuild – if it is an option you can afford and your long term plans are appropriate.

It is a credit to Porsche that their cars between 10 and 20 years old still look fabulous, drive beautifully and are generally affordable to maintain – and it is just the shorter overall life expectancy of the engines that create a potential financial disaster if owners expect them to last forever.

We still back their quality with our Lifetime Maintenance Plan that means for a modest monthly fee all servicing costs are covered in full (parts and labour) and the labour for most wear and tear replacements for parts that have failed (including engines).

Because of the increasing numbers of crankshaft bearing failure or cracked cylinders (and being consistent with our advice) we now exclude those specific failures from cover for future cars entering the plan that have exceeded 80K (although scored bores will still be covered).

This has created a minor contradiction because while we want to encourage owners to seriously consider the benefits of a pre-emptive engine rebuild - cars on the Plan would have had to await engine failure before being eligible for the benefits of their cover.

So although we expect to be working at full capacity for engine rebuilds for some years ahead - to address this anomaly – anyone who joined the scheme before the restriction of cover over the 80K limit for crankshaft/cylinder crack failures (who is automatically fully covered for the labour for a failed engine rebuild) will also now be offered a discount if they choose a pre-emptive rebuild at or after 100k - before failure occurs.

Similarly anyone who joins the scheme after the 80K restriction (who has covered over 100K) will also be considered for a similar discretionary discount for a pre-emptive rebuild.

It is too complicated and has too many variables to try and define the exact benefit for all circumstances so in both cases the discount will be discretionary and strictly on a case by case basis and taking into account (among others) how many years they will have been on the scheme, how many miles the engine has covered and the extent of the rebuild (the more comprehensive the better) but the intention is to agree a deal that benefits both parties through discussion. This will include those on the scheme that might be interested in an oversized engine pre-emptive rebuild.

We hope that by offering some additional financial encouragement to consider earlier preventative engine maintenance we are seen to be putting our money (or lack of it) where our mouths are and demonstrating how confident we are that on average more owners will benefit from a pre-emptive rebuild at (or over) 100K - than not - and that our advice is soundly and honestly based on our engineering experience.


Baz
 
Thanks Baz, Wasz and everyone else for their comments above.

As I see it there are two schools of thought - and similar to what we have seen on the IMS front. Those who favour pre-Emptive maintenance and those who would rather wait until things go Pop.

My car's previous owner clearly looked after her and she was regularly serviced with no expenses spared - all items identified on the OPC inspection being immediately sorted. I bought her (the car, not the owner) at 139K miles following the wisdom of condition over miles and she still puts a smile on my face every time I drive her. Unfortunately, the nature of my work and living in London means that she only gets driven on weekends and quite often only does short 10-15 min journeys and so barely gets warmed up before being switched off. I am sure that is not helping the cause at all but because I get to drive her so little I am less inclined to spend on the Rebuild because (1) the mileage means that there will be little impact on the value and (2) I am not quite sure whether I want to upgrade the car (I've been tempted by the 96/97 C4S's).

What would be very helpful though is to understand what the differential in rebuild costs would be for (1) a pre-emptive rebuild and (2) a rebuild associated with high mileage detonation e.g. crank bearing failure.

Appreciate that this may not be something that can be put onto a public forum but even an indication in terms of broad terms/percentages would be a good indicator for people facing this dilemna.

C
 
The thing is I believe many people are buying 996's as that's the only 911 they can afford, pretty much as I am.

Therefore you can probably accept some reasonably higher bills spread throughout the ownership but its hard to accept that relatively soon (assuming a higher mileage car with the wear and tear as described) a engine rebuild should be considered so Im assuming between £8-10k for this done properly. For the lower end of the market where these higher mileage cars are that's around 50% of the value of the car. That's a hard pill to swallow IMO. I think anyone would want to rebuild if they could, its more a question of do you want to commit financially that much into the car.

I totally understand the point of doing it if your keeping the car for a long time however its still hard one to accept. The offer above is also a good incentive however I'll admit its starting to change my mind a little as I simply cant afford to take on that responsibility at the moment. The same goes for earlier 997's so that about 10 years worth of 911's that are potentially quite a risk.

Im pretty sure Im going to take the gamble though. It may turn out to be financial suicide but hopefully not.
 
I'll try and answer the last 3 questions as best as I can.

Ragpicker - I would recommend a 10/50 and Millers Nanodrive.

Chipster - this is more complicated. If the crank went with no other damage you would need to add a crank and rod to the bill at around £2,500+ Vat, but more often than not the rod welds to the crank, snaps and damages the crankcases etc. If the heads are still Ok the cheapest way out of this is a replacement Porsche bottom end which for a 3.4 is around £4,550, a 3.6 £4,815 and a 3.8 £11,631 (all plus Vat) - but you still need the top end to be overhauled. cleaned and fitted and all the associated gaskets etc. and you still have the old designs with well reported weaknesses (although unlikely to strike again for many years ahead).

But heads are almost impossible to find used so if they are damaged as well a new engine is around £18K and £24K for a 3.4 and 3.6/7 respectively + Vat.

So a pre-emptive rebuild with the new parts fitted for around £7.500 + Vat that eliminates or protects the weak areas can make some comparative sense for those intending to keep and enjoy the car and benefit from the anticipated eventual appreciation.

Coulstar - Our maintenance plan was originally created exactly for your scenario because it enables the owners buying older cars (because that is all they can afford) to pay a modest monthly amount that covers the labour for most failures (including many wear and tear items), get free annual services (not extended to 2 years either) and means a subsequent rebuild under the scheme avoids the biggest cost - the labour charges.

It also means we can only benefit financially if we do such a good and thorough job during our free routine services (that includes the parts) that we rarely see the car again until the next service - benefitting the customer. If we do a poor job or miss things it only comes back to bite us in the form of extra labour costs we have to cover repairing the failure in between. We both have an incentive not to see the car more than once a year (unlike the incentive some may have by ignoring imminent faults and obtaining the additional cost of repairs during the year). We therefore share the benefits if we do a great job and suffer the consequences if we don't.

Our advantage is also admittedly regular monthly payments adding up to a smoother and more reliable cash flow and less of a need to pay for expensive advertisements to attract new customers as most remain with us throughout their Porsche ownership.

I don't think there is anyone else still offering such a scheme where they also have the highest reputation for their engine work, their future proofing inclusions and now a financial incentive to adopt the preventative maintenance option combined with the potential for boosting performance with an oversized rebuild option.


You do however have to undergo a full initial service check over before acceptance on the scheme so timing that with an annual service makes good sense. If such a check reveals faults that the owner cannot afford to fix just then - we also consider acceptance on the scheme with that specific item excluded permanently or until we fix it (unless it may have an impact on subsequent premature failures like for example a leaking radiator would have when we would exclude engine failures until it is fixed).

All these unique alternatives have been developed over the years because we started out to help owners afford to look after their cars properly on modest budgets and have tried to expand that as different problems emerged.


Baz
 
coullstar said:
a engine rebuild should be considered so Im assuming between £8-10k for this done properly. For the lower end of the market where these higher mileage cars are that's around 50% of the value of the car.

Or more like 100% of the car value if you bought 3 years ago.
I'd have to think very long and hard to justify spending £10k on a car that would be worth £12k when done. Now if leggy 996's were selling for £25k then that would be justification, may have to wait a very long time for that!

I'll just hope I've got a lucky one and enjoy it while I can.

P.s. It will cost less than £10k to convert it to electric at some point in the future! :bandit:
 

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