Posted: Wed Apr 08, 2015 4:55 pm Post subject: IMS data collection update - 132 cars (Page 3)
Just been looking at the data collected so far and thrown a couple of graphs together for folk to look at.
Here's a couple of bar charts showing which engines and models have sustained a failure:
Total number of failures - 9.8%
of which 3.4 - 0% and 3.6 - 13.3%
of which all X51 - 0%, C2 - 16.6% and C4S - 14.81%
Looking at the 6 failures reported I've done a graph displaying their mileage over time and 3 points - registered date, Failure date and data inputted date.
Notice how 5 of the 6 failures were all registered within a 12 month period and out of those, 3 of them failed within a few weeks of each other 9 years later.
Last reported failure was July 2014 and then June 2013 before that.
I'll do any updates in this post rather than the sticky so it doesn't get too messy in that post.
Once again, thank you to everybody involved. _________________ 2000 Manual 996 C4 Arctic Silver Convertible
Last edited by alex yates on Sat Dec 01, 2018 11:35 am; edited 6 times in total
Thanks for doing the analysis Alex. I'm still considering getting into an early car before prices begin to rise.
I suspect the % failure rate may be higher than the true norm for reasons discussed in the original thread.
Hopefully more data will continue to be added as this should increase the accuracy.
The breakdown between models is really interesting. Seems that some of the theories (such as early 3.4's are less prone to this kind of failure) are borne out in the sample.
Are you thinking of doing a level-headed bore score survey once this is completed? Might throw up some interesting patterns too? You can never have too much information and nice to see these issues discussed in a sensible way. _________________ 1997 993 Carrera S
GT4 Nordschleife
Joined: 08 Nov 2008 Posts: 30194 Location: Hertfordshire and Hampshire
Posted: Wed Apr 08, 2015 5:15 pm Post subject:
Is the best bet a 3.4 X51 (with LTT)?
I only ask as I have an option on one
alex yates Le Mans
Joined: 06 Mar 2014 Posts: 15287 Location: The Ribble Valley, Lancashire
Will be interesting to see how many have changed the bearing due to paranoia rather than need?
Difficult to prove that one, though. You could look at it the other way and it might be interesting to see if any bearings that have been changed consequently failed? If not (or the failure rate is significantly lower), it's difficult to say that changing is necessarily a bad thing, if the result is a lower failure rate and less paranoia? However, I suspect the current sample size is not big enough to be conclusive one way or the other. _________________ 1997 993 Carrera S
alex yates Le Mans
Joined: 06 Mar 2014 Posts: 15287 Location: The Ribble Valley, Lancashire
Will be interesting to see how many have changed the bearing due to paranoia rather than need?
Difficult to prove that one, though. You could look at it the other way and it might be interesting to see if any bearings that have been changed consequently failed? If not (or the failure rate is significantly lower), it's difficult to say that changing is necessarily a bad thing, if the result is a lower failure rate and less paranoia? However, I suspect the current sample size is not big enough to be conclusive one way or the other.
In the quiet words of the Virgin Mary... come again? _________________ 2000 Manual 996 C4 Arctic Silver Convertible
Chris_in_the_UK Estoril
Joined: 19 Mar 2014 Posts: 3542 Location: Harrogate
Posted: Sat Apr 11, 2015 7:49 am Post subject:
rottenbend wrote:
Chris_in_the_UK wrote:
Will be interesting to see how many have changed the bearing due to paranoia rather than need?
Difficult to prove that one, though. You could look at it the other way and it might be interesting to see if any bearings that have been changed consequently failed? If not (or the failure rate is significantly lower), it's difficult to say that changing is necessarily a bad thing, if the result is a lower failure rate and less paranoia? However, I suspect the current sample size is not big enough to be conclusive one way or the other.
Maybe I have not been clear?
I meant how many people had a perfectly running car with no issues but they have changed the bearing anyway as a precaution. I am not saying that changing it under these circumstances is bad, just curious how many were changed as a precaution. _________________ 2006 Cayman S PCCB's
rottenbend Magny-Cours
Joined: 22 Aug 2010 Posts: 2588 Location: Hertfordshire
Will be interesting to see how many have changed the bearing due to paranoia rather than need?
Difficult to prove that one, though. You could look at it the other way and it might be interesting to see if any bearings that have been changed consequently failed? If not (or the failure rate is significantly lower), it's difficult to say that changing is necessarily a bad thing, if the result is a lower failure rate and less paranoia? However, I suspect the current sample size is not big enough to be conclusive one way or the other.
In the quiet words of the Virgin Mary... come again?
Sorry it was a bit late when I wrote that and I misinterpreted Chris's post.
I think the choice of whether or not to change/modify the bearing seems to depend very much on the type of bearing. This has been talked about for a while and this dataset seems to support those theories. If I bought a 3.4 I probably wouldn't bother, other cars I might do it as preventative measure:?:
What is for certain is that the more owners know about this issue and how it may or may not affect their car, the better more informed decisions they can make. Which can only be a good thing _________________ 1997 993 Carrera S
rottenbend Magny-Cours
Joined: 22 Aug 2010 Posts: 2588 Location: Hertfordshire
I meant how many people had a perfectly running car with no issues but they have changed the bearing anyway as a precaution. I am not saying that changing it under these circumstances is bad, just curious how many were changed as a precaution.
_________________ 1997 993 Carrera S
alex yates Le Mans
Joined: 06 Mar 2014 Posts: 15287 Location: The Ribble Valley, Lancashire
I'll post some info over the weekend on replacements.
9962 C2 X51 3.6 replaced at 49,000 (preventative)
9962 C4S 3.6 Bearing replaced for peace of mind and showed minimal play. Dust shields removed
9962 C2 3.6 Parr replacement - preventative - original found to be in perfect condition. Bearing replaced for peace of mind and improve residual value of car
9962 C2 3.6 IMS replaced October 2014. Replaced IMS with modified kit from Northway alongside with new RMS which needed doing. Mix of Porsche and Specilalist history
9962 C4S 3.6 replaced twice in the space of a few months by the previous owner at Parr (original replacement LNS? failed very quickly and engine was leaking oil?). assuming it actually failed, the original was replaced Q4 2012
9961 C4 3.4 replaced by me at 95k as a preventative measure. Bought from Pelican parts. Single row bearing used to replace double row. Old bearing was in perfect condition.
9962 Anniversary 3.6 Upgraded Hartech bearing now fitted
9962 C4S 3.6 I had the bearing replaced when I bought the car as a preventative maintenance thing (LN bearing). (The original turned out to be fine BTW).
9962 C4S 3.6 IMS was replaced in February 2011 during Hartech engine rebuild. The rebuild was primarily to fix bore scoring, I assume IMS was replaced as a preventative measure rather than failure.
9962 C4S X51 3.6 Previous owner elected to go for a replacement clutch/RMS seal/IMS bearing (ceramic I think) during a major service in 2001 @ 12,000 miles. Not due to any problems but rather as a preventative/upgrade.
9962 C2 3.6 bearing: Original removed but was till in good order, @58k , bearing 2: Hartech, no seals: Removed but still in good order, @85k, bearing 3: Hartech, no seals: Currently fitted.
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