Quote:
Originally Posted by ozzy1
To be honest, even though I appreciate the effort here, I don't understand what the point is..
Second chart says that, as the part gets more use, the probability of it failing increases. Well we know that. Also, there is major 'undetermined' bias in the population of the data, where we don't know who we are not hearing from and who we really are hearing from (driver/maintenance etc habits, part specifics such as which cnc it was built in - long story there but I have seen failures of identical parts being produced in multiple cnc's and having different life due to placement of the cnc in the factory (i.e. exposed to afternoon sun or not).
So no offense or anything but unless the sample size is near 1% of N52s I would not draw any conclusions.
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I will be the first to agree with you that this is non-ideal. I am sure BMW know what the failure probabilities are, but it's not like they are talking.
It is unfortunate that there is some population bias, as in the people most likely to view the thread are ones searching for "water pump". There is also the so-called enthusiast bias, but whether that has a significant effect on pump life is questionable. But it is what it is, and it is about the best we can do in such a setting as this. I agree that we are likely getting over-estimates of the failure rate in the bins where we have a reasonable amount of data.
I view this more of an educational exercise and a curiosity for these very reasons. Regardless, it is interesting to know that I may only have a 30-40% chance of getting more than 100k miles on my water pump. Knowing this, I should reasonably expect a failure and should have educated myself on the warning signs/what to do (and educated my wife who often drives the car).
I would have liked to design the survey with many factors, but it is hard enough to get a reasonable number of response as is...
What can I say, I'm a data person, even if it is flawed. Althought flawed data in the wrong hands can be more dangerous than anecdotal evidence, I still prefer it.
Quote:
Originally Posted by woodpecka
I think there is a simple conclusion and you do what you want with it;
There is a high level of probability to have a water pump failure after 70-100 k and the impact is very important. So, spending 350-400$ and a few hr to change the pump as prevention is not a bad idea.
At the end, you decide if you want to take the risk..
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I don't endorse preventative changing or not, as you said. I personally probably would not do it until close to 100k if at all, and that would be if I planned to keep the car for significantly longer. It depends on a lot, including warranty status, risk tolerance, and usage.
Ultimately, it sucks that there is a reasonably chance of getting stranded by a failure like this during the normal ownership period.