Discussion
Say someone was buying a 997, the prevailing consensus seems to be to get the bores checked for scoring.
However to clarify, is this to look for excessive scoring? How is excessive scoring defined? Does any form of scoring equate to bad news?
Helping a friend of a friend who is buying a 997 in the midlands...
However to clarify, is this to look for excessive scoring? How is excessive scoring defined? Does any form of scoring equate to bad news?
Helping a friend of a friend who is buying a 997 in the midlands...
There is a difference between longitudinal polish marks and scoring.
The cylinder is much harder than the piston and when a face seizure occurs the big problem is more the deterioration of the piston surface than the cylinder bore - but you cannot see the piston face without stripping the engine -and you can only see the cylinder bore with a camera with lighting that reveals polish marks and make then often look serious - which they are not - they are just the result of an initial very slightly rough honed surface being polished more by the rings in some places than others but do not have any measurable depth or mechanical consequences.
Although a badly scored bore should be obvious to anyone - experience of looking at lots of engine and stripping and rebuilding them allows specialists to interpret the difference in marginal cases - that others may miss-interpret.
However once scoring has taken place (however minor and in however few cylinders) the writing is on the wall and at some time in the future the engine will need rebuilding or replacing.
Most Independent Porsche Specialists should be able to determine the differences but it requires the removal of shields and coils and is not a five minute job.
Easier signs are rear N/S exhaust more dark and oily, and a ticking noise (often thought to be piston slap but more often caused by the instability of uneven firing pulses causing a snatch in the camshaft chain drive system (that can occur even without cylinder scoring) or can be a tappet etc.
Finally - just because a car does not have cylinder scoring yet - does not protect it from failing in the future - so I would advise any prospective purchaser to have in place some reliable warranty or access to resources to fix the problem if it occurs in their ownership.
All this can unfortunately put people off from buying a superb car that will probably not let them down and will already incorporate prices reflecting the slightly less reliable performance of a few of the engines.
Baz
The cylinder is much harder than the piston and when a face seizure occurs the big problem is more the deterioration of the piston surface than the cylinder bore - but you cannot see the piston face without stripping the engine -and you can only see the cylinder bore with a camera with lighting that reveals polish marks and make then often look serious - which they are not - they are just the result of an initial very slightly rough honed surface being polished more by the rings in some places than others but do not have any measurable depth or mechanical consequences.
Although a badly scored bore should be obvious to anyone - experience of looking at lots of engine and stripping and rebuilding them allows specialists to interpret the difference in marginal cases - that others may miss-interpret.
However once scoring has taken place (however minor and in however few cylinders) the writing is on the wall and at some time in the future the engine will need rebuilding or replacing.
Most Independent Porsche Specialists should be able to determine the differences but it requires the removal of shields and coils and is not a five minute job.
Easier signs are rear N/S exhaust more dark and oily, and a ticking noise (often thought to be piston slap but more often caused by the instability of uneven firing pulses causing a snatch in the camshaft chain drive system (that can occur even without cylinder scoring) or can be a tappet etc.
Finally - just because a car does not have cylinder scoring yet - does not protect it from failing in the future - so I would advise any prospective purchaser to have in place some reliable warranty or access to resources to fix the problem if it occurs in their ownership.
All this can unfortunately put people off from buying a superb car that will probably not let them down and will already incorporate prices reflecting the slightly less reliable performance of a few of the engines.
Baz
Quick question.
My brother in laws father, driving his 37K mileage 996 Cab down through France and the engine goes kaput.
17K quote from OPC, local Indie does it for 11K.
The only info I can get from my Bro in Law (he doesn't know an engine from a steering wheel) is that he is sure his father stated that when they took the engine apart they found rust in the sump, and this pointed to the problem.
Any ideas what this may have been? Frustratingly thats as much info as I can get.
My brother in laws father, driving his 37K mileage 996 Cab down through France and the engine goes kaput.
17K quote from OPC, local Indie does it for 11K.
The only info I can get from my Bro in Law (he doesn't know an engine from a steering wheel) is that he is sure his father stated that when they took the engine apart they found rust in the sump, and this pointed to the problem.
Any ideas what this may have been? Frustratingly thats as much info as I can get.
hartech said:
That will almost certainly be the result of the first signs of a cylinder crack allowing coolant to drop back into the engine and down into the sump.
Baz
Cheers for that Baz. Out of interest, is this a common fault associated with the known faults with this engine or more a one off? Baz
I did try to get him to send the car up to you, alas by the time I found out, the work was already being carried out locally .
hartech said:
There is a difference between longitudinal polish marks and scoring.
The cylinder is much harder than the piston and when a face seizure occurs the big problem is more the deterioration of the piston surface than the cylinder bore - but you cannot see the piston face without stripping the engine -and you can only see the cylinder bore with a camera with lighting that reveals polish marks and make then often look serious - which they are not - they are just the result of an initial very slightly rough honed surface being polished more by the rings in some places than others but do not have any measurable depth or mechanical consequences.
Although a badly scored bore should be obvious to anyone - experience of looking at lots of engine and stripping and rebuilding them allows specialists to interpret the difference in marginal cases - that others may miss-interpret.
However once scoring has taken place (however minor and in however few cylinders) the writing is on the wall and at some time in the future the engine will need rebuilding or replacing.
Most Independent Porsche Specialists should be able to determine the differences but it requires the removal of shields and coils and is not a five minute job.
Easier signs are rear N/S exhaust more dark and oily, and a ticking noise (often thought to be piston slap but more often caused by the instability of uneven firing pulses causing a snatch in the camshaft chain drive system (that can occur even without cylinder scoring) or can be a tappet etc.
Finally - just because a car does not have cylinder scoring yet - does not protect it from failing in the future - so I would advise any prospective purchaser to have in place some reliable warranty or access to resources to fix the problem if it occurs in their ownership.
All this can unfortunately put people off from buying a superb car that will probably not let them down and will already incorporate prices reflecting the slightly less reliable performance of a few of the engines.
Baz
Thanks Baz, very helpful response. The cylinder is much harder than the piston and when a face seizure occurs the big problem is more the deterioration of the piston surface than the cylinder bore - but you cannot see the piston face without stripping the engine -and you can only see the cylinder bore with a camera with lighting that reveals polish marks and make then often look serious - which they are not - they are just the result of an initial very slightly rough honed surface being polished more by the rings in some places than others but do not have any measurable depth or mechanical consequences.
Although a badly scored bore should be obvious to anyone - experience of looking at lots of engine and stripping and rebuilding them allows specialists to interpret the difference in marginal cases - that others may miss-interpret.
However once scoring has taken place (however minor and in however few cylinders) the writing is on the wall and at some time in the future the engine will need rebuilding or replacing.
Most Independent Porsche Specialists should be able to determine the differences but it requires the removal of shields and coils and is not a five minute job.
Easier signs are rear N/S exhaust more dark and oily, and a ticking noise (often thought to be piston slap but more often caused by the instability of uneven firing pulses causing a snatch in the camshaft chain drive system (that can occur even without cylinder scoring) or can be a tappet etc.
Finally - just because a car does not have cylinder scoring yet - does not protect it from failing in the future - so I would advise any prospective purchaser to have in place some reliable warranty or access to resources to fix the problem if it occurs in their ownership.
All this can unfortunately put people off from buying a superb car that will probably not let them down and will already incorporate prices reflecting the slightly less reliable performance of a few of the engines.
Baz
I think i'll tell him to avoid the 997 as he won't have a warranty and i was hoping a camera could determine a possible issue. However i will mention your lifetime warranty just in case he is willing to travel to bolton.
hartech said:
There is a difference between longitudinal polish marks and scoring.
The cylinder is much harder than the piston and when a face seizure occurs the big problem is more the deterioration of the piston surface than the cylinder bore - but you cannot see the piston face without stripping the engine -and you can only see the cylinder bore with a camera with lighting that reveals polish marks and make then often look serious - which they are not - they are just the result of an initial very slightly rough honed surface being polished more by the rings in some places than others but do not have any measurable depth or mechanical consequences.
Although a badly scored bore should be obvious to anyone - experience of looking at lots of engine and stripping and rebuilding them allows specialists to interpret the difference in marginal cases - that others may miss-interpret.
However once scoring has taken place (however minor and in however few cylinders) the writing is on the wall and at some time in the future the engine will need rebuilding or replacing.
Most Independent Porsche Specialists should be able to determine the differences but it requires the removal of shields and coils and is not a five minute job.
Easier signs are rear N/S exhaust more dark and oily, and a ticking noise (often thought to be piston slap but more often caused by the instability of uneven firing pulses causing a snatch in the camshaft chain drive system (that can occur even without cylinder scoring) or can be a tappet etc.
Finally - just because a car does not have cylinder scoring yet - does not protect it from failing in the future - so I would advise any prospective purchaser to have in place some reliable warranty or access to resources to fix the problem if it occurs in their ownership.
All this can unfortunately put people off from buying a superb car that will probably not let them down and will already incorporate prices reflecting the slightly less reliable performance of a few of the engines.
Baz
To me the engine always sounds broken in these cars, like bricks in a washing machine, so ticking noises they all seem to have them, mine certainly does. I know it's ok as you guys did a boroscope and said it was of the cleanest engines you'd seen. The cylinder is much harder than the piston and when a face seizure occurs the big problem is more the deterioration of the piston surface than the cylinder bore - but you cannot see the piston face without stripping the engine -and you can only see the cylinder bore with a camera with lighting that reveals polish marks and make then often look serious - which they are not - they are just the result of an initial very slightly rough honed surface being polished more by the rings in some places than others but do not have any measurable depth or mechanical consequences.
Although a badly scored bore should be obvious to anyone - experience of looking at lots of engine and stripping and rebuilding them allows specialists to interpret the difference in marginal cases - that others may miss-interpret.
However once scoring has taken place (however minor and in however few cylinders) the writing is on the wall and at some time in the future the engine will need rebuilding or replacing.
Most Independent Porsche Specialists should be able to determine the differences but it requires the removal of shields and coils and is not a five minute job.
Easier signs are rear N/S exhaust more dark and oily, and a ticking noise (often thought to be piston slap but more often caused by the instability of uneven firing pulses causing a snatch in the camshaft chain drive system (that can occur even without cylinder scoring) or can be a tappet etc.
Finally - just because a car does not have cylinder scoring yet - does not protect it from failing in the future - so I would advise any prospective purchaser to have in place some reliable warranty or access to resources to fix the problem if it occurs in their ownership.
All this can unfortunately put people off from buying a superb car that will probably not let them down and will already incorporate prices reflecting the slightly less reliable performance of a few of the engines.
Baz
A question: my car emits a low pitch quiet buzzing noise from around front wheels when engine running, only noticed it as I changed a front wheel with engine running. I'm assuming it's the PASM or TPMS, is it normal, only does it when running, can't tell if rear buzzes due to engine noise?
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