996 MK1 Engines
Discussion
Doing further research into the 996 and have a query in that are the later / last 3.4 engines less problematic than early ones?
I remember reading somewhere that after 2000, engines where less prone to failure.
Any further information or guidance would be great.
Plus I have read the Hartech site info.
I remember reading somewhere that after 2000, engines where less prone to failure.
Any further information or guidance would be great.
Plus I have read the Hartech site info.
Take the advice of the various online guides to the 996/997 engines with care as the guidance has changed quite a lot over the years and is still not universally agreed.
I recall that at first the 3.4 engine was to be avoided due to D chunking and the 3.6 was better. Then the advice changed to avoid the 3.6 due to single row IMS bearing and get a 3.4. The latest seems to be avoid 3.6 and later 3.4 due to bore scoring and get an early 3.4 due to the better piston coating.
A 3.4 996 is at least 15 years old now, I would suggest buying on the condition of the car and do not discount any particular car just because of year of manufacture.
I recall that at first the 3.4 engine was to be avoided due to D chunking and the 3.6 was better. Then the advice changed to avoid the 3.6 due to single row IMS bearing and get a 3.4. The latest seems to be avoid 3.6 and later 3.4 due to bore scoring and get an early 3.4 due to the better piston coating.
A 3.4 996 is at least 15 years old now, I would suggest buying on the condition of the car and do not discount any particular car just because of year of manufacture.
Good advice above, but the even easier way is:
change the (10W-50 Millers CFS NanoDrive ideally) oil as often as you can
don't rag it from cold,
fit a low-temp thermostat
keep coolant system in top order (check hoses, pump, etc every two years max)
and don't worry about it too much.
Most of the cars will be modded now where needed and have engine failures priced in (i.e. leaves you a slush-fund in the bank).
change the (10W-50 Millers CFS NanoDrive ideally) oil as often as you can
don't rag it from cold,
fit a low-temp thermostat
keep coolant system in top order (check hoses, pump, etc every two years max)
and don't worry about it too much.
Most of the cars will be modded now where needed and have engine failures priced in (i.e. leaves you a slush-fund in the bank).
We had a 2001 Cab I think up to 06/07, when passed on it was as good as new at 110tkm, never missed a beat. It did a mix of loads little wife shopping trips, me taking it on long runs round EUR and some spirited spanking it round local tours, even took it to track a few times for a laugh. Only had the regular services. Not all were bad.
When deciding what to get recently I had a good chat with my Porsche independant who services my cars and his opinion was that 3.4 or 3.6 996 engines were pretty good, IMS failures were very Rare as we're bore score .
He did how ever advise me to stay clear of the 3.8gen 1 997S as bore score is a major issue.
He did how ever advise me to stay clear of the 3.8gen 1 997S as bore score is a major issue.
Our on line guide is old now and ha been completely re-written to be more reader friendly and changed to a "click on" subject system to delve into more detail, with "click on" photos and even video links - but is not yet completely finished - hoping to be on line soon with the video links added over time. A brief 10 minute video is available showing much of our rebuild processes - both on line (via our web site www.hartech.org) or we will send a copy FOC to any legitimate club organisers or Porsche specialists wanting more information to absorb or show prospective customers.
Things have changed as we saw more examples - newer models and of course could assess the numbers failing of each type and the causes - however there is nothing in the old guide that was proven wrong.
To re-cap - as models increased in bore size (and stroke) the basic block size remained the same but the cylinder walls got thinner. That increase in pressure pushing on the cylinder walls combined with thinner walls resulted in gradual ovality and cracking mainly in 3.4 engines (most of which together with all earlier smaller engines had a piston coating that survived with the bore material Lokasil).
The last 3.4's had the newer piston coating as did all that followed but because the greatest face load is with larger later engines - fewer failed.
Later Cayman, 3.6 and 3.8 engines seem to be slower to go oval (but still do) possibly because of a change from Lokasil 1 to Lokasil 2 (which had larger silicon particles) - but these in turn cause more rapid deterioration of the piston coating when they break free due to their larger particle size trapped between the piston and the cylinder wall.
The original incidences of failure of the dual row small bearing were similar to the single row that replaced it (that specs slightly better due to greater ball side wall depth) but removal of the end seal to allow lubrication by engine oil makes either better.
The later larger bearing (especially without a seal) seems to completely solve that problem.
I would not say that the 3.6 has less problems technically. There is the fact that someone choosing a 3.6 over a 3.8 may be les inclined to drive it as hard.
In overall terms we get about the same number of 3.4's (although they are older), Caymans and 3.6's in as each other and three times as many of each of those (or the same overall combined) of 3.8's (a comparison of numbers sold of each type might help assess comparative reliability).
Bore scoring is the biggest problem now and replacement cylinders can be provided in steel, iron or alloy with Nikasil finish (as used on all reliable Porsche engines for decades).
We find some steel and iron liners (fitted elsewhere) move in the remainder of the cylinders because the remaining alloy outside is so thin and weak and due to the differential expansion rates (and the steel cylinder head gasket design) and cause problems and often are asked to replace these with our own Aerospace Nikasil cylinders with huge success (as used by the majority of successful racing engines in the UK) and costing about the same due to our investment in automated machinery - providing the perfectly matched expansion rates for the pistons, better thermal conductivity and a very long life surface.
Failure rates for cam chains, crankshaft bearings and valve seats are quite rare but are another cause of rebuilds.
I would guess overall reliability is not that different to most similar modern sports car performance engines.
Cooling can be a problem which LTT, alloy cylinders and extra radiator can assist with providing the third radiator is temperature controlled.
Baz
Things have changed as we saw more examples - newer models and of course could assess the numbers failing of each type and the causes - however there is nothing in the old guide that was proven wrong.
To re-cap - as models increased in bore size (and stroke) the basic block size remained the same but the cylinder walls got thinner. That increase in pressure pushing on the cylinder walls combined with thinner walls resulted in gradual ovality and cracking mainly in 3.4 engines (most of which together with all earlier smaller engines had a piston coating that survived with the bore material Lokasil).
The last 3.4's had the newer piston coating as did all that followed but because the greatest face load is with larger later engines - fewer failed.
Later Cayman, 3.6 and 3.8 engines seem to be slower to go oval (but still do) possibly because of a change from Lokasil 1 to Lokasil 2 (which had larger silicon particles) - but these in turn cause more rapid deterioration of the piston coating when they break free due to their larger particle size trapped between the piston and the cylinder wall.
The original incidences of failure of the dual row small bearing were similar to the single row that replaced it (that specs slightly better due to greater ball side wall depth) but removal of the end seal to allow lubrication by engine oil makes either better.
The later larger bearing (especially without a seal) seems to completely solve that problem.
I would not say that the 3.6 has less problems technically. There is the fact that someone choosing a 3.6 over a 3.8 may be les inclined to drive it as hard.
In overall terms we get about the same number of 3.4's (although they are older), Caymans and 3.6's in as each other and three times as many of each of those (or the same overall combined) of 3.8's (a comparison of numbers sold of each type might help assess comparative reliability).
Bore scoring is the biggest problem now and replacement cylinders can be provided in steel, iron or alloy with Nikasil finish (as used on all reliable Porsche engines for decades).
We find some steel and iron liners (fitted elsewhere) move in the remainder of the cylinders because the remaining alloy outside is so thin and weak and due to the differential expansion rates (and the steel cylinder head gasket design) and cause problems and often are asked to replace these with our own Aerospace Nikasil cylinders with huge success (as used by the majority of successful racing engines in the UK) and costing about the same due to our investment in automated machinery - providing the perfectly matched expansion rates for the pistons, better thermal conductivity and a very long life surface.
Failure rates for cam chains, crankshaft bearings and valve seats are quite rare but are another cause of rebuilds.
I would guess overall reliability is not that different to most similar modern sports car performance engines.
Cooling can be a problem which LTT, alloy cylinders and extra radiator can assist with providing the third radiator is temperature controlled.
Baz
EGTE said:
"The later 3.6-litre engine is pretty much problem-free. "
RPM told me that the only pattern of problems with the m96 3.4 that they see is the ims bearing.
They also advised that - again, in their experience - m96 3.6 is much more problematic, suffering from scoring and in the case of an engine they are currently rebuilding a broken valve spring (piston hit valve).
As a buyer,you need to appreciate the difference between sudden catastrophic failure Eg ims bearing, and excessive wear Eg bore scoring. These are different flavours of "reliability ". I'm sure all points of view are valid, but it is confusing when they appear to conflict.
Imho you need to buy the right car with an engine that's ok on the day. Then decide whether to exercise preventative measures or trust to luck. It seems pretty clear there is no absolute consensus over which m96 engine is most "reliable", or how to realistically ensure you buy a car with that engine.
They also advised that - again, in their experience - m96 3.6 is much more problematic, suffering from scoring and in the case of an engine they are currently rebuilding a broken valve spring (piston hit valve).
As a buyer,you need to appreciate the difference between sudden catastrophic failure Eg ims bearing, and excessive wear Eg bore scoring. These are different flavours of "reliability ". I'm sure all points of view are valid, but it is confusing when they appear to conflict.
Imho you need to buy the right car with an engine that's ok on the day. Then decide whether to exercise preventative measures or trust to luck. It seems pretty clear there is no absolute consensus over which m96 engine is most "reliable", or how to realistically ensure you buy a car with that engine.
Just to be sure you all understand that "Bore scoring" is a sudden catastrophic event. Wear of or bubbling of the piston coating occurs first and some coating loss usually follows (bit the bores will still be unmarked at this stage), then there is an occasion when a particle of lose silicon impacts against the cylinder bore and piston and drags more parts free of the cylinder wall and in a few seconds the score is evident.
Thereafter deterioration takes more time (because the damage creates more clearance between the piston and the bore so allowing more particles to detach but escape only gradually making things worse).
Yes it takes time to stop the engine but the actual event is sudden and unpredictable (and the eventually consequences a catastrophe for anyone).
Baz
Thereafter deterioration takes more time (because the damage creates more clearance between the piston and the bore so allowing more particles to detach but escape only gradually making things worse).
Yes it takes time to stop the engine but the actual event is sudden and unpredictable (and the eventually consequences a catastrophe for anyone).
Baz
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