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Discussion summary
YOUR RESEARCH996.2 3.6 Sooting Left Exhaust
Reported or suspected cause
where the owner resorts
Reported cause
No successful repair reported for this finding.
1
Identified cause
0
Suspected cause
0
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Read evidence and context
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Reported cause
A common resolution for this issue is where the owner resorts to cleaning the tailpipe thoroughly and moving the car on.
Leading evidence: 'where the owner resorts' (1 discussions report identifying this cause; no attributable repair resolution). Across 1 matching discussions, the most frequently mentioned possible cause is 'where the owner resorts' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Check fuel trims' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Clean tips, taken a dipstick measurement and noted
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No successful repair reported for this finding.
0
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0
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Performed · outcome unconfirmed · Original poster
Have done that exactly, cleaned the tips, taken a dipstick measurement and noted.
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Performed · outcome unconfirmed
I scratched my head and changed the coil pack on #4.
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Performed · outcome unconfirmed · Original poster
The car has had lower temp thermostat, new water pump and all radiators, coolant hoses etc replaced last year.
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Performed · outcome unconfirmed · Original poster
I had previously only used the display oil measurement to track oil levels so will start comparing oil consumption based on a dipstick measurement.
That said, I still wouldn’t go straight to a diagnose bore score from light dry soot alone, especially if there’s no driver-side tapping, no oil use, clean plugs and the AOS has already tested OK.
Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.
58 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
911uk: 1 discussions
0 evidence records excluded for query context · 0 excluded by outcome qualification · 0 adjusted by outcome qualification.
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Outcome without a verified action link
Most are still not rebuilt, but more are being done every day.
Hi All,
My new to me 996.2 C2 has some slight sooting on the left exhaust tip and wanted to see if this was normal or not as seeing mixed responses on the forums.
The car is on 90k, has been serviced every year or 5k and is currently on Millers Oils CFS 10W-50 NT+.
Since buying the car I have done 400 miles, some motorway and some spirited driving.
The oil has been 1-2 from max on the display and half way between min and max on the dipstick when I bought the car and after the 400 miles.
However I have noticed a light misting of soot on the left tailpipe. Is this normal? Anything to be worried about?
The previous owner had done the manometer test across the AOS and proven it to be OK a few months ago. The car also had new plugs and service few months ago with zero oil or fouling on the plugs.
Lastly, is there a correct way to check oil? Should I do it after the oil is at 90 and rested 15mins to collect in the sump? Or should I do cold?
Thanks and any help appreciated!
Pics attached of tips after the 400 miles - after wiping left tip, can see it’s generally darker than the right tip.
Bore score symptom unfortunately. Are you getting any tapping from the engine on the driver's side? Oil should be checked hot and wait like you say, not cold.
Will do on next oil change.
Think best thing is to monitor oil consumption and clean the tips and see if the sooting continues!
Will there be sooting if the engine oil was overfilled? just asked the previous owner and he said he filled to just below max on the dipstick when engine was hot.
Previous owner also mentioned the NS bank warms on a rich mixture whilst the OS bank is up to temp, is this true?
Thanks
Sorry Chief, but I think you're in for a spot of bother. The only way to tell is by borescoping each cylinder to see whats going on. It sounds like 2 owners ago was selling pups to move the car on.
You pic above shows quite a bit of soot for 400 miles.
What you do next depends on the condition of the cylinder walls. A rebuild is somewhere in this cars future.
No nice way to say it unfortunately.
No worries, unfortunate but a risk I have taken. And the best way to borescope fully is with the sump off?
Anyone suggest a good Indy to take the car to in Surrey?
Soot on one tip can be bore score related, but I wouldn’t use light dry soot on its own as the diagnosis. It can also come from normal exhaust flow bias, cold-start richness, short journeys, a slight fuelling imbalance, lambda/MAF adaptation, AOS vapour or even the silencers distributing flow unevenly.
The important distinction is dry soot versus oily/wet deposits. If there’s no driver-side tapping, no oil use, clean plugs and the AOS has tested OK, I’d monitor it rather than panic. Clean both tips, do a few hundred miles, track oil use properly and see if one side gets heavily sooty again. If oil consumption rises, the tip becomes wet/oily, or tapping appears, then it’s borescope time.
On a 996.2 3.6, soot on one tip is worth keeping an eye on, as bore scoring is one of the known worries on these engines. That said, I still wouldn’t go straight to a diagnose bore score from light dry soot alone, especially if there’s no driver-side tapping, no oil use, clean plugs and the AOS has already tested OK.
Same as stated above, then If one side gets heavily sooty again, the tip becomes oily, oil consumption rises, or tapping appears, then it’s borescope time.
Hi
Monitor carefully, but also start saving for a full engine rebuild. That is in all probability what is going to be required. Enjoy the car until then. Usual advice of do not let car idle to "warm up", ie set off immediately, and do not pull away in a high gear ever, especially from cold.
All the best
Berni
I had previously only used the display oil measurement to track oil levels so will start comparing oil consumption based on a dipstick measurement.
I see many post that they have not topped oil up between services and others say up to 1L per 1000 miles is OK. What is acceptable? And does spirited driving consume more?
Sure, I am happy to pay for a rebuild if this is required as it seems to be the only way to be sure the engine is OK at this age/mileage. However, if it can be avoided for a while, that will also be better.
Thanks for the advice, have been following that in my short tenure!
BS from the best bs'ers in the Porsche community. Like all the shite they are peddling, they of course can "train" technicians on this special borescoping technique, which is of course the "best way".
You can scope it yourself now, you only need bank 2. Plenty of write-ups here/online, but I understand if having done no work on the car it feels daunting.
Only saying this because it's unlikely you will find someone in Surrey that will not rob you blind for the bore scoping (think >300).
I have just bought my pal an endoscope from eBay, 33 pounds.
After he borrowed mine he just had to have one.
You can easily remove plugs 6 and 5. 6 is the likely culprit, remove the air box to access the crank bolt to turn the engine over until no 6 is at bottom dead center and you will soon see if there is scoring.
I hope it is not.
Just to add take a few photos and post them here for an opinion.
This ^. You can also put the car in 6th gear, jam the rear left rotor with a screwdriver and use a breaker bar to turn the rear right wheel to turn the engine. If needed, the rear bumper is 10 minutes to remove.
Ive found my car will use a bit of oil if I rev it out properly but on a long gentle drive it'll not use a drop. If both tips were doing the same thing then id not be too worried but the fact the one side is on its own would get me wanting to scope it out as people have said. Best of luck!
Out of interest what oil are you running on?
At this moment in time I'd clean the tips up, get on a thicker better oil and possibly fit a low temp thermostat. This will at minimum slow the progression of it and give you time to decide/save, etc. I'd also be monitoring the oil consumption and the tailpipes. If there's no tapping from bank 2, then it's possibly only very light and not much different than most Gen 2 cars out there.
You can also get it scoped or do a compression test and compare all cylinders.
Another option is to get Millers oils to do an oil analysis test on your oil too. They know all about scoring and can detect it in their test.
I thought the previous owner was running the 10w50 but he has said it had 5w40 Millers CFS NT+ in its last service. I plan to change to the 10w50 equivalent on next service and get the oil sent off for analysis with Millers.
I think I will do a personal borescope this weekend, and keep monitoring the oil consumption. As mentioned previously,
I had only been using the electronic oil readings which were fluctuating from 1-2 off the max levels.
Taking a dipstick reading the oil is at half way between min and max and the oil was just below full at its service 1100miles ago. Will keep monitoring.
It is below the quoted Porsche allowance but still seems high to me compared to some who have no oil top up between services.
The car has had lower temp thermostat, new water pump and all radiators, coolant hoses etc replaced last year.
If you can perform the borescope yourself, great. All borescopes are not created equal, however, and not all are capable of giving clear decisive pictures of inside each cylinder. I have a cheap Draper one which is okay but it lacks the movable neck at the camera end. Instead it has a mirror that attaches to the camera end and gives a right-angle view. This is more likely to fall off in the cylinder than perform any great photographic feats.
Another valuable insight from doing it yourself is that you can look at the spark plugs and take an early view right away. A seriously scored cylinder will have an oil fouled plug. If you pull a nice light brownish one, you are either clear or in the earlier stages.
Start with cylinder 6 and work onwards through 5 and 4 (the off side of the vehicle). The normal pattern of wear is in this order. Often 3,2,1 are still mild and asymptomatic even when 6 and 5 are far gone and have become noisy at idle. You will have to move the crank pulley each time to get a deep view into each cylinder.
If you want it done professionally, I've used ePorsch in Surrey for this exact job before. It was around 200 pounds 2.5 years ago, but I can say that they are experts in this process and will produce excellent quality photos that clearly show any damage. They will also of course advice you further on repairs, I think they mentioned 10k plus for a rebuild at their workshop.
This positive experience with ePorsch was when I was looking at buying a car from another nearby dealer (they also sell cars themselves but pre-emptively scope any vehicle which arrives to them prior to sale), and I had noticed a noisy idle. The op situation is of course different since we are post-purchase and must therefore look for economy where possible.
On my own car, shortly after purchase I noticed a coating of dry fluffy (not oily) black soot in the exhaust manifold of cylinder 4 when removing it to drill and replace the rusted bolts. Other cylinders on that side, 6 and 5 were clean. I scratched my head and changed the coil pack on #4. This also cured a cold hesitation from low RPM that I had experienced. I mention this to show that soot can indeed have other origins in addition to scoring.
Either way, pull the plugs on the off-side bank and post pics of them here, plus any photos you manage to take with a scope inside the cylinders.
No oil between services says more about the way they are driven than the cars themselves. But yes a healthy motor when not pressing it can consume no oil, despite the age.
I got my borescope camera from Ali Express, it has a second camera facing sideways. Articulating neck is obviously better but I imagine way more expensive than the 20 quid I spent.
this forum is mad…
here’s another suggestion… leave the car undiagnosed, give it a wash and sell it. At thr moment you have a bit of soot on your tip - could be almost anything, paying for potentially extremely bad news and associated knowledge that prevents selling without disclosure is rather daft. Once you sell save hard for a car with a dfi engine and forget all about the troublesome 996/997.1 with associated £20k rebuild costs
the cost of a 996.2 at the current moment is cheap (infact very similar to the E46 M3 I sold to buy it) and the cost disparity between a previously engine rebuilt car and a car that hasn't has a difference of roughly £10k. Whilst I could have bought a rebuilt car, or a DFI engine car at a premium, the car is a weekend car for me and rebuilding an engine will give me the peace of mind I wouldn't have with a car that could also crap itself after I paid a premium for it.
I am only borescoping the car as it will cost me next to nothing and it's relatively easy to do and I'd rather know then not. Apart from the slight black soot after a heavy weekend of spirited driving, the car has been brilliant.
Something to consider: as It’s your weekend car you probably won’t be putting loads of miles on it. If the engine indeed has borescore and its relatively minor, you could be 5-10k miles away from loud tapping if you drive it sympathetically, use thicker oil, change the oil often, etc. That could equate to a few more years of happy motoring before it requires a rebuild.
Yes agreed! I have no symptoms at the moment and only manage 2000 miles or so a year in the weekend cars so it could be a while before I need to fork out.
I plan to do annual changes with 10w50 CFS NT+ so hopefully helps the cause (if there is a problem in the first place
)
You may pay more up front and a premium for a dfi car but cost of ownership will most likely be way less than your 996, it will be easier to sell and will depreciate less. As the market awareness of the risks associated with 996/997.1 they will become increasingly difficult to sell- I know those who live on this forum would have you believe otherwise and that a 996 is cheap but actually it seldom is. As for buying a car then straight away paying for a rebuild surely yiu are in effect paying a similar premium for a frankly way inferior car. Of course you can sell your chosen pathway how you like but in the not unlikely event that you have to spend £20k with no apparent upgrade, just to keep you were you are, on your car and then when you eventually sell it you will reflect on what it has cost you perhaps your stand point won’t seem so attractive.
Are there really people who would sleep better at night (comparatively) if they didn't diagnose it? What sort of weird mental gymnastics is that? Are you disclosing the soot was there then to potential buyers? Because if you clean the soot and say nothing about it your hands are not exactly clean are they?
Are you tricking god or some such?
Lavan - All hope is not lost. I have a rebuilt motor with Nikkies and low tension oil control rings. I still get soot and occasional smoke on start. Some M96’s pool oil more than others…nature of the flat six beast.
Check the oil after sitting overnight on a level surface, same way every time. Manometer test is easy. AOS is a real ***** and has been known to fail (even just fresh from the box) because it can. I check mine before every track day, even though I have the UAOS. If your oil consumption is within limits, monitor and get a UOA after 3k miles. Others mention borescope may be helpful, but unless you scope above the piston, you might not see damage for early stage scoring.
Any fuel smell on start? It may not be too long before the other bank starts sooting up if the issue is injector related. If you have a scanner that can check your fuel trims, that’s a plus. My personal experience was heavier soot on left (bank 2), with less soot on right. Replacing the injectors with new was the trick.
Thanks pal, My Foxwell NT530 arrived today so will do some fuel trim scans. Plan to do the manometer test too, just waiting for an oil cap I can modify to test with and hopefully I can do some troubleshooting.
I do not think I get any fuel smell on startup, will check again when I take the car out tomorrow. Forgot to mention, the previous owner did fit a new Lambda sensor on Bank 2 sensor 2 (post cat) as the previous one was failing and was outside of spec when scanned.
are you really trying to suggest that a dfi engine is as crap an ownership proposition as its predecessor just because a company whose business model is to actively market the extremely high failure rates of the m69 engine to promote its services is now saying it has seen some failed dfi engines? Shame on you, you must know that whilst a number of any mass produced product will have a number that will fail the dfi engine is very reliable, especially so if compared to the previous unit. This forum is full of inaccurate memes propagated by posts like yours
I don't want a 997.2 as I don't think they are as fun or engaging as my 996.
I buy my cars to drive and so a 997.2 is a downgrade for me personally.
Sure if all you are thinking about is a few quid that's fine but it's not my reason for owning cars.
The M96 has been around for almost 30 years now since the first Boxster 2.5. Most are still not rebuilt, but more are being done every day. My 996.2 4S hasn't been yet at 150k so they don't all blow up.
My other car, a 991.1 has the 9A1 DFI which has 124k miles and has also failed to blow up luckily.
The oldest DFI engines are now 18, so they are now well into the zone of potential repairs being required. A recent 991.1 GTS in here had bore score and a broken exhaust valve. That cost the owner about 15k to buy a donor engine. That said they do enjoy a generally superior reputation for reliability having only 2 chains and no IMS.
Both engines have their merits and character but we will need to see what the next decade brings for the 9A1 in order to make a true long term comparison.
The issues around the short comings of the M9x engines made themselves known alot closer to new than the 9A1 engines. Hence the reputation and nervousness in the market for those engines
1. can you articulate how your 996 is more fun and more engaging than any version of the 997.2? Neither of the 996’s I had were anywhere near the 997.2, chiefly because of the way superior characteristics of the matter’s power and drive train
2. Most folk buy cars to drive, prey how is superior power unit, stiffness and handling of the 997.2 a downgrade for a sports car?
3. In what world is £20k, the potential repair bill of
I also agree with SidewaysSi and know others that have owned both and agree too, its all matter of opinion and its fine that yours is different based upon your experiences. A fettled 996 is one of the sweetest driving 911's imo, they have the best steering feel, a 997.2 is a fantastic car but much more sterile and a lot of that comes from them being too refined (for me). If I had one car I had to daily drive and use for fun too then a 997.2 would make more sense but as a sole 'fun' car, id much rather have a 996 with aforementioned 'fettling'.
Also, you do realise youre posting in the 996 section of the forum, which of course youre welcome to do but posting about how much better you believe the 997.2 to be in here is a waste of time.
This is an open forum, I don’t need your approval to post. You and others you know may prefer a 996 over a 997, doesn’t mean that many others prefer the 997 Over 996. Without free opinions those without experience using this forum to help decide whether to buy a 996 will get a skewered understanding of the 996 if all views aren’t mentioned so my mentioning my own experiences is not a waste of time. Many folk can only have one daily car, maybe they should understand that it might not be a 996 - as you admit yourself.
Enough already!!!
This is Lavan's thread, it is about asking advice on what might or might not be bore scoring and not about the merits and opinions of one model over another so lets get back to helping Lavan with some constructive advice.
A common resolution for this issue is where the owner resorts to cleaning the tailpipe thoroughly and moving the car on.
The hit from purchase price down to WBAC pricing is heavy, but still not as much as a six cylinder rebuild.
A full Hartech engine is around 15k but up to a third of that could come back upon resale as a strong selling point.
Most owners investing in a 996 don't have a further purse of 15k for an engine build unless they bought the car at a knockdown price due to already known engine issues.
As an old mechanic once said to me many years ago, sell it whilst it's still running.
Most traders assume that 996.2 in auctions are likely to be bore scored and bid accordingly. Plenty of YouTube traders have bought inexpensive 996.2 cars from auction and invariably discover that an otherwise running and driving car has the issue.
There are no inexpensive solutions to bore scoring, sadly.
