I created a 958 survey. So far - the only data in it is me. If you formerly owned a 955/957 V8 (and reported it here) and now own a 958 - you can find that survey at http://bit.ly/958GoBoom

I'll be very interested if anyone reports a failure.

 

Need to make sure the 958 respondents don't get confused between bore scoring, transfer case failure, and cam tensioner bolts, and that it's just scoring being reported.

 

The survey is quite specific about that, as was my announcement of it - and in general - most of the 958 owners are capable of understanding that.

 

Thanks for that. I was wondering if and when we would get to see the results.
I hope you update them in the future. I would think there will be a bunch more in the next few weeks, and then tapering off.

Yes, I filled it out. 05 Turbo, 120k, no scoring, not too worried about it, Porsche should pay.

 

Thank you for the poll I shy of 160K on my 08 S so far so good but I'm not holding my breath need to sort out some weird cold start transmission stuff ASAP. Mine lived in Wisconsin for most of its life.

 

I'll give another interim report later this week. We have over 50 responses to the 955/957 survey now. I was hoping for 100 - but I don't think we'll make that in a reasonable time.

 

Hi Don,

Another critical piece of data is the MY and engine that actually failed. I suspect that the MY 2008 4.8 are going to have more failures than others, dependent one which contractor supplied the engine block. The current survey shows only the survey-takers MY and engine in the aggregate, not that of the engine failures. For instance, my 2008 4.8 failed at 93k... There are five of us who have had failures. How many are 4.8s?

Thanks for doing this!

Best,
Tom

 

Tom - actually it's fairly trivial for me to figure out what year/engines failed. while it may show the data in the aggregate, I can also view it to the individual response level - and by looking at people reporting failures (5 at the moment) - I can then look at what year/engine they're reporting. The data is there - it just might not be immediately obvious.

 

I just did the survey - thanks for setting it up so well. Very clear logic in the questions.

2004 S, bore scoring engine failure at about 45k miles, replaced with crate engine from Porsche with Porsche partial goodwill, back in 2009. Still running at 103k now.

BTW, I think a major factor may be skewing these poll results to underreport failures - people who have that failure are most likely to just ditch the car, and after doing that, will be biased away from reading this forum.

 

Entirely possible - but probably balanced by the people who just drive their Cayennes and haven't even heard about bore failures, and have never visited a Cayenne forum. There is no way to make it completely accurate without compelling people to fill it out and then depend on them filling it out honestly.

At least in this case - we can get a feel for the numbers. One thing that I found interesting - in the beginning - there were WAY more turbo owners responding to the survey (with failures and without) - that's sort of evened out now. Is that because turbo owners are more "involved"? Might be - can't think of a lot of other reasons - the normally aspirated certainly sold more than the turbos. It could go with the theory that more NA owners are simply viewing it as "it's just transportation" (anyone who knows where that line came from wins a beer from me..) Dunno. Happily I made early disclaimers that it isn't statistically significant survey.

 

Great! Care to share the info?

Cheers,
Tom

 

When I have enough responses..

 

Updated Data - based on 68 vehicles

I thought I'd update the data since there are some threads where speculation seems to be winning out over data. These are interim results. I'd like to see 100 responses to the survey - at which point I think we can start to trust some of the data.

OK - so the first section is going to be from the aggregate data:

OVERALL DATA (All Vehicles):

FAILURE REPORTED



The following questions don't always add up - we have 8 failures reported, but not all of the people reporting failures answered all the questions..








NO FAILURE TO REPORT:



ALL VEHICLES (Non-Failure and Failure):




SOME INTERIM CONCLUSIONS:

Out of 68 vehicles reported on 8 suffered bore failures. That's around 12%. It's not 100%, it's not 1%. It's close to what I hypothesized earlier (10%).

Individual Failure Report Data:

Out of the 8 failures:

• 2008 Turbo, failure at 90-120k
• 2007 Turbo, (non-US) at 60-90K
• 2008 Turbo, failure at 90-120k
• 2006 Turbo, failure at 60-90K
• 2005 Normally aspirated, failure at 60-90K
• 2004 Normally aspirated, failure at 30-60K
• 2005 Normally aspirated, failure at 60-90K
• 2008 Turbo, failure at less than 30K

Conclusions:

• The 2008 turbo seems over-represented in failures - but without knowing the ratio of turbos to non-turbos sold - a solid conclusion can't be reached.
• Mileage of failure - 1/2 are in the 60-120K range, 1/4 in the 30-60k range, one outlier reporting a less than 30K failure.
• There are a significant proportion of the vehicles that have NOT experienced a failure at greater than 120,000 miles.

I hope people continue visiting the survey and entering their data. The data will only be as accurate as the number of people who respond.

 

This is a fun idea, but one shouldn't make ANY conclusions about incidence due to biased reporting plus a grossly inadequate sample size. Hopefully you all realize the results from this kind of thing end up being no different than random chance and are as reliable as speculation.

 

What sample size would you suggest?

So far - the speculation here has been based on a few reported failures - some of them reported numerous times eliciting different comments and theories each time. I would love to have data from every V8 Cayenne sold - but that's not going to happen, and as someone pointed out - even Porsche won't have that data since some people who experienced the failure simply junked the car, which Porsche would know nothing about or the reason for junking it.

Right now - it's the best info we have unless you can point to any better source (would love to have one..) for more accurate numbers. To me the most interesting take on the numbers here is - not ALL V8's seem to suffer this fate (as some people have claimed..) At least not in what would be considered a reasonable lifetime for a vehicle (120,000 miles?) And the problem isn't limited to certain year/models - at least not what we can see with the limited sample size we have.

One thing you can do to help - encourage everyone you know with a 955/957 V8 to do the survey - get more numbers. The more numbers we have the better the conclusions will be.

BTW - "biased reporting" - I have no horse in this race. I sold my '06 V8 3 years ago. I have a 958 Turbo - which so far - the 958's haven't experienced this sort of issue. We have other issues - but no reports of this one to date.