Knackered old Porsche with loads of miles - 996 content
Discussion
Just a quick update on the old bus.
It's still going strong and still racking up the miles. It had a new clutch slave this weekend as it was just starting to leak - a 30 minute job on a 996 and to be fair it was overdue as it hadn't been changed at the last clutch swap due to arriving late in the post. The only other failure to report is the hands free mic on the stereo has packed up.
The motor still shows no signs of getting near end of life but the rear diff is just starting to make the tell tale noises of a well used item, I suspect in the next 20K or so this will need a rebuild which would be nearly 350K miles between gearbox rebuilds so not bad going!
It's still going strong and still racking up the miles. It had a new clutch slave this weekend as it was just starting to leak - a 30 minute job on a 996 and to be fair it was overdue as it hadn't been changed at the last clutch swap due to arriving late in the post. The only other failure to report is the hands free mic on the stereo has packed up.
The motor still shows no signs of getting near end of life but the rear diff is just starting to make the tell tale noises of a well used item, I suspect in the next 20K or so this will need a rebuild which would be nearly 350K miles between gearbox rebuilds so not bad going!
J4CKO said:
This popped up on FB and thought it may be of interest.relevant, apologies if been posted before.
https://www.carthrottle.com/post/how-much-power-wi...
Brilliant! There are so many of these cars out there now with well over 200K on them and still going strong, yet so many internet folk will still tell you they'll explode at any second and cost you your house if you buy one https://www.carthrottle.com/post/how-much-power-wi...
Just a little update, nothing broken and nothing falling off. It's off to Austria in a few days so we'll see how it copes with that.
As we all know at this time of year many Porsches are garaged or otherwise stored away for winter. Meanwhile I'm seriously considering washing mine and perhaps even refitting the arch liner properly.....:
Only 2000 miles of brake dust and grime
With the cold weather now back my rattle at start up has come back again, if the ambient is over 12 degrees or so it is silent but when it gets down to the temps we've been having recently I get a distinct rattle for 30 seconds or so. It's done this since I owned it so no major drama here, it seems to get a little worse each year but then it's got another 40K+ miles on it each year too
It's either the timing chain tensioners or a tappet that's lazy when the oil is thick. Hardly worth taking it apart to work out what at this stage - it would have made a bid for freedom by now if it was really bad and I've heart of freshly rebuild motors doing the same thing, clearly a feature 
As we all know at this time of year many Porsches are garaged or otherwise stored away for winter. Meanwhile I'm seriously considering washing mine and perhaps even refitting the arch liner properly.....:
Only 2000 miles of brake dust and grime
With the cold weather now back my rattle at start up has come back again, if the ambient is over 12 degrees or so it is silent but when it gets down to the temps we've been having recently I get a distinct rattle for 30 seconds or so. It's done this since I owned it so no major drama here, it seems to get a little worse each year but then it's got another 40K+ miles on it each year too
It's either the timing chain tensioners or a tappet that's lazy when the oil is thick. Hardly worth taking it apart to work out what at this stage - it would have made a bid for freedom by now if it was really bad and I've heart of freshly rebuild motors doing the same thing, clearly a feature Edited by poppopbangbang on Monday 7th November 23:10
eltax91 said:
Still loving the thread. Since its arrival I'm more and more tempted with a 996 at the 10-12k end of the spectrum.
A fair few adverts mention 'no IMS bearing issues at this mileage'. I've read the posts you made before about double or single row etc. Is there a common wisdom that, once the car has hit a certain mileage, then you've gone past the IMS failure window?
It's probably the only thing stopping me taking the plunge. The thought of a £5k engine rebuild with little or no warning of failure is horrifying!
Double row cars have something like a 0.7% failure rate, single row is nearer 7% although having said that if they're post 100K then either are probably going to be fine. On a double row engine other bits will wear out and break before the IMS fails...... unless it's a weird one like mine that keeps slogging on A fair few adverts mention 'no IMS bearing issues at this mileage'. I've read the posts you made before about double or single row etc. Is there a common wisdom that, once the car has hit a certain mileage, then you've gone past the IMS failure window?
It's probably the only thing stopping me taking the plunge. The thought of a £5k engine rebuild with little or no warning of failure is horrifying!
A 98 or 99 car should be a dual row bearing engine which if it's made it to 80K odd is realistically going to go on until something else breaks.
I reckon mine has 50K or so left in it before it will need some serious work, the gearbox will need a rebuild at this point as the rear diff has just started to get a slight whine that's slowly increasing. At that point it would probably be worth pulling the engine apart to see what's what. It will have passed 600K KM by that point though so as life goes that's not bad for a road car!
So update time and a fair bit is afoot......
The last oil test showed a high copper count compared to what is normal for the car, around 500ppm vs pretty much zero. It had also developed a bit more of a meaty rattle from cold start than usual shortly before this test. The engine was just North of half a million KM at this point.
Whilst performance was still good and there was no excess oil consumption or similar I made the decision to pull it at this point to investigate further as running it until it went pop was never the plan which revealed:
No 1 bearing showing wear to the copper, the failure mode for this was a timing chain guide starting to break up and shedding material which damaged number 1 crank bearing in turn leading to rapid wear. Just one of those things but a preventative change of timing chain guides every 200K miles would remove the chance of this happening. The crank is fine aside from some very slight marking on number 1 journal that will clear with a polish and no other bearings were overly worn. The big ends and all the remaining crank bearings were still totally serviceable and the rods still measured within spec for roundness on both ends.
The bores showed no scoring and were in great condition aside from normal wear at this mileage (beyond Porsche ovality limits but then it's got more than half a million KMs of up and downs on them so that is to be expected), pistons were fine and rings were still sealing well. The IMS bearing was mint and had absolutely zero play in it and the IMS shaft and sprocket were mint, timing chains were still in good condition so it was just a wear related failure of the guides which clearly are at life at 500K KM.
The oil pressure pump was in pretty decent condition with just a couple of minor scores in the ally housing from where the debris that had taken out no 1 crank bearing had gone through it. Both scavenge pumps were mint as were their drives. The cams and tappets were again mint with the surface hardening on the cams undamaged and no dished or soft tappets. The valve guides were well worn as were the valves, all 24 were still sealing but the stems measure thinner in the centers and at least two have a bit of stretch in them, again not surprising given how many KMs the engine has covered and how it has been used.
It's worth noting this car has always run 0W/40 Mobil 1 on a 10K - 12K mile service interval. It has always had coolant and oil temp before being heavily loaded but aside from that it's not been pampered or overly looked after. If anything a lot of what it has been through would be considered abuse by some as it's not shy of track work or donuts!
Based on this I'd say 500K KM is life for a 3.4 M96 used and serviced as this one has been - at this point the valves and guides are heavily worn, the bores are at the Porsche limit for ovality and the chain guides are worn to the point of fairly graceful failure. For a mass produced engine which makes just shy of 90bhp/litre I don't think that's bad at all, especially as it was making good power right up until I called time on it and to be fair to it would have gone a bit further still albeit at the risk of the crank being damaged beyond use.
So the plan:
As the bores are past the ovality limit then there are a few options to return them to round but in the interests of not messing about and given the opportunity for a performance increase then the block will be getting liners, which at the same time will convert it to a closed deck design and 100mm bore for 3.7L total capacity. Pistons will be low expansion forged items with a reduction in skirt and therefore friction and weight. Components will be made by Capricorn with Autofarm carrying out the engine build, Autofarm did my C2 which is still going (very) strong to this day. IMS bearing is a bit of an unknown as there are no more dual bearings available anywhere so short of running the old one again I am probably going to go with an oil fed roller bearing in place of a ball bearing. Heads will be refurbed with new valves, guides and seats freshened up but the majority of bits such as cams, crank, rods, major castings etc. will be used again. Having covered the distance they have it's pretty clear that all the castings are good (and well stress relieved given the amount of heat cycles they've done!) and there are no casting issues or material defects with rods, crank, cams etc. basically having got this far if they were going to fail they would have by now so I'm not keen on replacing them with unknown bits just for the sake of it.
Power should be in the region of 360bhp which compares nicely to a Mk1 GT3 and it should do half a million KM again without too much fuss, although this time around I will be doing chain guides at half that distance as they're a proven failure point.
Cost wise, you can buy quite a decent 996 for what this is going to cost but then again it costs £390PM to lease a diesel BMW on 20K miles a year and I do a lot more mileage than that so if I see another three years from the car then it's cost me no more than driving a diesel three series..... I know what I'd rather have
The last oil test showed a high copper count compared to what is normal for the car, around 500ppm vs pretty much zero. It had also developed a bit more of a meaty rattle from cold start than usual shortly before this test. The engine was just North of half a million KM at this point.
Whilst performance was still good and there was no excess oil consumption or similar I made the decision to pull it at this point to investigate further as running it until it went pop was never the plan which revealed:
No 1 bearing showing wear to the copper, the failure mode for this was a timing chain guide starting to break up and shedding material which damaged number 1 crank bearing in turn leading to rapid wear. Just one of those things but a preventative change of timing chain guides every 200K miles would remove the chance of this happening. The crank is fine aside from some very slight marking on number 1 journal that will clear with a polish and no other bearings were overly worn. The big ends and all the remaining crank bearings were still totally serviceable and the rods still measured within spec for roundness on both ends.
The bores showed no scoring and were in great condition aside from normal wear at this mileage (beyond Porsche ovality limits but then it's got more than half a million KMs of up and downs on them so that is to be expected), pistons were fine and rings were still sealing well. The IMS bearing was mint and had absolutely zero play in it and the IMS shaft and sprocket were mint, timing chains were still in good condition so it was just a wear related failure of the guides which clearly are at life at 500K KM.
The oil pressure pump was in pretty decent condition with just a couple of minor scores in the ally housing from where the debris that had taken out no 1 crank bearing had gone through it. Both scavenge pumps were mint as were their drives. The cams and tappets were again mint with the surface hardening on the cams undamaged and no dished or soft tappets. The valve guides were well worn as were the valves, all 24 were still sealing but the stems measure thinner in the centers and at least two have a bit of stretch in them, again not surprising given how many KMs the engine has covered and how it has been used.
It's worth noting this car has always run 0W/40 Mobil 1 on a 10K - 12K mile service interval. It has always had coolant and oil temp before being heavily loaded but aside from that it's not been pampered or overly looked after. If anything a lot of what it has been through would be considered abuse by some as it's not shy of track work or donuts!
Based on this I'd say 500K KM is life for a 3.4 M96 used and serviced as this one has been - at this point the valves and guides are heavily worn, the bores are at the Porsche limit for ovality and the chain guides are worn to the point of fairly graceful failure. For a mass produced engine which makes just shy of 90bhp/litre I don't think that's bad at all, especially as it was making good power right up until I called time on it and to be fair to it would have gone a bit further still albeit at the risk of the crank being damaged beyond use.
So the plan:
As the bores are past the ovality limit then there are a few options to return them to round but in the interests of not messing about and given the opportunity for a performance increase then the block will be getting liners, which at the same time will convert it to a closed deck design and 100mm bore for 3.7L total capacity. Pistons will be low expansion forged items with a reduction in skirt and therefore friction and weight. Components will be made by Capricorn with Autofarm carrying out the engine build, Autofarm did my C2 which is still going (very) strong to this day. IMS bearing is a bit of an unknown as there are no more dual bearings available anywhere so short of running the old one again I am probably going to go with an oil fed roller bearing in place of a ball bearing. Heads will be refurbed with new valves, guides and seats freshened up but the majority of bits such as cams, crank, rods, major castings etc. will be used again. Having covered the distance they have it's pretty clear that all the castings are good (and well stress relieved given the amount of heat cycles they've done!) and there are no casting issues or material defects with rods, crank, cams etc. basically having got this far if they were going to fail they would have by now so I'm not keen on replacing them with unknown bits just for the sake of it.
Power should be in the region of 360bhp which compares nicely to a Mk1 GT3 and it should do half a million KM again without too much fuss, although this time around I will be doing chain guides at half that distance as they're a proven failure point.
Cost wise, you can buy quite a decent 996 for what this is going to cost but then again it costs £390PM to lease a diesel BMW on 20K miles a year and I do a lot more mileage than that so if I see another three years from the car then it's cost me no more than driving a diesel three series..... I know what I'd rather have
Krikkit said:
Well that was unexpected!
Having got towards the bottom of the condition report I was expecting "put it all back together as standard and away we go", not "chuck a set of forged pistons in and give it a good going over".
At 500kKM that's not bad condition though, be interesting to see if you're the highest-mileage non-Porsche-owned M96.
If the bores still measured up within spec then it would have gone back together as was with fresh bearings, chains, rings and guides but as they didn't there are limited options. Running it further like this just results in the ovality getting worse until you get into ring pack sealing issues or a failure of the bore. It is possible to hone them oversized and the get them back to OE tolerance by Nikasil coating them but then you have taken some mechanical strength out of a component that is already a weak link in this engine. Having got towards the bottom of the condition report I was expecting "put it all back together as standard and away we go", not "chuck a set of forged pistons in and give it a good going over".
At 500kKM that's not bad condition though, be interesting to see if you're the highest-mileage non-Porsche-owned M96.
By biting the bullet and going liners/closing the deck it solves this problem. Fresh pistons at this mileage would make sense regardless and the cost difference between liners and pistons in 96mm or 100mm is essentially zero so 3.7 it is! Capricorn do all our F1 stuff so I'm pretty confident it will do the trick and Autofarm have a lot of experience of this. Plus a bit of extra poke is never a bad thing
Coakers said:
Well it took me a good hour+ but I thoroughly enjoyed that. Makes my mk2 golf build a tad boring 
Are you undertaking the rebuild yourself PPBB? And yes I second the motion for you to provide plenty of details/pictures for the rebuild. Thanks for sharing.
I quite enjoyed your Mk2 Golf Build to be honest! :-) Are you undertaking the rebuild yourself PPBB? And yes I second the motion for you to provide plenty of details/pictures for the rebuild. Thanks for sharing.No Autofarm are doing the building, whilst I would rather like to put it together myself the time required and specialist tools needed make it impractical - plus there is a huge amount to be said for handing it over to an engine builder who puts one or two of these together every week, it's very hard to put a price on that sort of experience especially when you need it to work for the next 1/4 of a million miles. For me this is definitely a case of the more you know the more you have to learn and I'm well aware of the bits where I could f**k this up royally
chuntington101 said:
Are Capricorn just doing the liners (guess custom one offs?) or more? Have heard their name coming up in the aftermarket world but can't find much on what services they offer.
Capricorn (or rather Capricorn Automotive as Capricorn are a massive group) are doing liners and pistons including the machining of the original block and liner fit, there are also some additional operations required on the original block for coolant flow etc. due to closing the deck. They are mostly an F1/Pro-Motorsport/OEM supplier rather than tuner market but a few do have parts produced by them if they are not cost limited. They also do a lot of parts and service for our VJ/CK/TJ F1 motors.http://www.capricorngroup.net/en/kolben/service/
Autofarms 3.7L Cayman is using the same approach so it's fairly well proven. Just the cost of doing this is many, many times more than banging a Nikasil ally sleeve down there.
chuntington101 said:
Is there any reason for not going for a turbo motor?
I'm not really a fan of a turbo motors power delivery and they are inheriently less reliable and heavier due to the higher component count. Also in my experience the GT1 based motors (Turbo/GT3) have less life than the M96 and generally require a looking at which costs much more than an M96 at 200K miles or so. Used properly a dual row M96 will clear at least 250K miles - this is probably a sore point as my experience of 996 generation 911s seems to be at total odds with the entire internet...... in the real world the difference between 350bhp and 450bhp isn't actually that much, both cars can cruise at 160mph so over several hundred miles being a few seconds quicker to 160mph doesn't make much difference especially when you probably have an additional fuel stop due to running richer mixtures than the NA engine.John D. said:
He said what?!
Yeah I know I'm not trying to be controversal here but this M96 managed well north of 300K miles without the heads coming off. Out of my (Awwww) Porsche Friends a 996 Turbo melted an exhaust valve at 170K miles and a 997 GT3 had a timing chain failure. So out of a sample of four the three GT1 based motors have been the least reliable with one not being opened as yet, while the s
t unreliable M96 has been the most reliable - based on mileage covered for heads off engine repair. I should quantify this, I'm talking about the total mileage before rebuild here (not overall reliability of engine type before it is lifed) and I'm only talking about the early 3.4L M96 with dual row IMS bearing and ferrous coated pistons. Any single row or plastic coated piston engines then the usual caveats apply but an early 3.4 will in my experience run longer than any normal person will realistically need if you feed it the oil that Porsche say, at the intervals they say and don't be a dick from cold or when it's stinking hot having sat in traffic - all those caveats apply to the Turbos and GT3s too though which should do the same thing.
The bottom line as I see it from having done well over half a million miles across two 3.4L 996 is that the issues reported on the M96 are actually to do with the later 3.4L single row cars and the 3.6L cars. These had some pretty major revisions to engine internals which quite frankly didn't work and these cars do have inherrent issues with about a 10% chance of the motor suddenly becoming in need of rebuild. The 3.4s on the other hand are at about 0.7% from Porsches data and the class action data from the states (and that includes some single row engines) but they got tared with the same brush too. On top of this a lot of scaremongering from those with an interest in flogging upgrade bits and half understood information being repeated by owners has really done the M96 a disservice as in it's original, none cost-down form it was a proper unit capable of big miles with minimal power loss and when it does finally wear out it does it gracefully not catastrophically.
r129sl said:
Congratulations on a superb thread and an even better attitude. I just love the story of this car. It is great to hear about a car—or any machine for that matter—being used to its full potential. The story really glorifies the quality of the machine so much more than a Nurburgring lap time or a Wales road test ever could. And as you might expect, I applaud the approach of maintain, repair and improve. Far better than throw away and replace.
There isn't really anything I could replace it with I don't think..... I did look around a year or so back but a 997 is just a less reliable 996 that's less hackable electronically and not a lot else combines the fuel efficiency, interior space and pace that this does. It has always been a case with this of as stuff wears out, fit better stuff so the engine is just in keeping with that. Not a lot to report at this stage aside from the block is waiting at Capricorn and there is a big box of bits from Porsche ready for when it comes back. ETA at the moment for being back in the car and running is towards the end of Feb - I miss it very much!
TheLordJohn said:
I don't know if you've said already, but what are you using in the meantime...!?
This:
A totally standard PPP'd WRX Wagon that I purchased completely sight unseen and sent the cash for it via BACS off the back of a couple of text messages.... probably best not to follow my car buying practices if we're honest although I did the same with the Porsche some years ago
I have a bit of a past with Subaru/Prodrive so when I spotted this browsing e-bay during a meeting it seemed the logical choice as it's still a flat engine and burns fuel at a similar rate to the Porsche Paddy_N_Murphy said:
'Tis the Off-Season surely for schnell schnell motorsport parts delivery?
No it's the worst time of year for doing anything Motorsport related - it's "Silly Season" as we call it when EVERYONE is trying to get stuff made/rebuilt/machined/fettled but we're on schedule on my lump and I'll post a few pictures once it's all back from machining Diesel Meister said:
Anyway - this thread just keeps on giving! A 3.7 with 360bhp will be perfect in this. Can't wait as more build pictures come through. Any plans for other upgrades? Wheels (I could see this on some nice, lightweight but low-key custom jobs made to look "OEM+", not that he current ones have anything wrong with them)? Strategically placed lighter panels? Or is the latter a bit of compromise too far (cost / effectiveness for road use)?
Not really no, I like the fact it looks like a very slightly lower standard car - that's a big plus to me really and as the split rims crack tested up fine when they were rebuilt a while back they have plenty of life left in them at this point. Plus I put quite a lot of work into fitting the brakes under them so it'd be a shame to waste that With regards panels as it stands now the lights, front wings and bonnet are all pence off e-bay in the right colour as Boxster bits are a straight fit as well as 996 parts. Likewise for the rad ducts and various other front end bits. The rear bumper is also cheap as chips in the correct colour as it is standard across all the first generation 996. As it's very likely to get bumped, banged and knocked purely because it's out and about so much I'd rather keep it all easily and cheaply replaceable. My target was always to get it to 996 GT3 weight and we've pretty much managed that with no major compromises/expensive bits or uncomfortable lightweight seats
pokiou said:
Hey PPBB,
Got a quick question, i know you covered that you changed the radiators.. but how have you managed to keep the car sitting at 90c degrees constantly. I can barely keep mine under 100c degrees on a cold night?
Im at my ends wits and dont know which way to go. I'm also looking at the CSF radiators just wanted your opinion before i continue down that expensive road.
Your thread gives me more confidence in my 156.000km 1998 996 c2... I too believe the car got a bad rep and people just went with it.
98 C2 will be dual row IMS and ferrous coated pistons - at 156K KM it's got another 300K KM odd in it no problem Got a quick question, i know you covered that you changed the radiators.. but how have you managed to keep the car sitting at 90c degrees constantly. I can barely keep mine under 100c degrees on a cold night?
Im at my ends wits and dont know which way to go. I'm also looking at the CSF radiators just wanted your opinion before i continue down that expensive road.
Your thread gives me more confidence in my 156.000km 1998 996 c2
... I too believe the car got a bad rep and people just went with it.A few things are different on my car to most 996, the engine has a lower temperature (72 degree C) thermostat fitted which opens sooner than the standard thermostat. The car also has no aircon hence my radiators are completely exposed to the ambient airflow down the rad ducts rather than being partially shielded by the aircon condensers, a second point on this is that the aircon condensers (when the aircon is on) heat the ambient airflow before it reaches the radiators which reduces the efficiency of the standard radiators when compared to them running with no aircon condensers fitted. Finally my fan on/off temps are set lower than a standard car, the fans go immediately to high speed when activated and constantly run at low speed below 60KPH to provide additional airflow to the rads at slow speeds.
One of the issues (for want of a better term) with the 996 is that it has a huge coolant capacity and therefore A LOT of thermal mass in the coolant, this means once it is hot it takes quite a bit of time to get this energy back out of the coolant and into the ambient atmosphere. If you can stop it getting that hot in the first place by increasing the cooling systems ability to shed heat to atmosphere you are in a much better position
Hope this helps!
ooid said:
A manual fan switch (incl. 2 stages) + Oil temperature gauge should have been standard/essential items in both 996 & 986, imho. 
I've cheated somewhat as the Evo5 logger in the nose reads the coolant temp and vehicle speed from OBD2 and then pulls the fan relays down accordingly but you do have a point 
stevesingo said:
Up and running yet?
Close! 
Took a while to get through Capricorn as they were flat out on F1. It ended up with my engine castings via Autofarm and two of our F1 blocks on the same waiting list.... always a problem when you are trying to get stuff done over silly season.
Not a lot to report on the motor other than it is built and should last a very, very long time. There are a few bits in there which had to be changed due to original parts being NLA and I took the decision to refurb my original heads rather than go for new ones (the cost difference wasn't much at all) as after this many heat cycles it's a fair bet my original head castings are thoroughly stress relieved and if there was any porosity that was going to cause a problem it would have shown up by now. The quality from Capricorn to Autofarms spec is brilliant, the machining work is to the same level of precision and finishing as the F1 engines I am used to working with..... which as it's been done by the same machinists is no real surprise but certain aspects, like the opening up of coolant passageways to cool the upper section of the liner, have been executed very, very well.
Really looking forward to getting back to piling the miles on it now and very interested to see what the difference in performance is between this motor and the old one. Not only has this one got a bump in capacity but the frictionals should be a fair bit lower too. I've kept the standard cam profiles and dual mass flywheel as driveabiliy is a really key thing to me as I do so many miles in it so whilst it would definitely go a fair bit better with some more aggresive cams in there I think we should see a decent increase in poke on the standard ones with no impact to idle or low speed driveability. At some point once it has a few thousand miles on it I'll run it on a chassis dyno to see where we have ended up power wise.
One thing that might need a bit of attention is the ECU calibration, I have previously played around with this but found the square root of naff all power wise - unsurprisingly the Porsche calibration is very good. When I went to equal length manifolds and GT3 throttle body there was no drama in supporting this and when I compared data back to back the MAF was correctly seeing the increase in air flow and the injector pulse width had lengthened accordingly. However with an extra 0.3L I suspect we might be over what the standard calibration can support, the car has a decent data logger, widebands etc. on it so it's a quick job to tell if it is. We'll just have to see
Gassing Station | Readers' Cars | Top of Page | What's New | My Stuff