Does replacing working parts make sense?
12-16-2007, 10:57 PM
#16
Burning Brakes
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Jim
12-16-2007, 11:13 PM
#17
Rennlist Member
If it ain't broke, don't fix it.
Some of my worst stranded-by-the-road episodes turned out the be caused by brand new parts I had just installed. I'm not sure about replacement auto parts in general, but for electronics parts there is a known failure curve with a big bulge in the first 100 hours or so, which ramps down afterwards and continues at a low and steady level for 20 years or so. The bulge even has a name - infant mortality. Again, I don't have data on auto parts, but my experiece says very strongly that they do follows the same curve. In fact it feels like it is quite a lot worse. If this is correct it might be explained because replacement parts (even new ones) have either been sitting on the shelf for 20 years or they were recently produced to 20 year old specs. I think the quality of newly produced parts goes down when the car goes out of production becaues you no longer really have the QA guys at the factory monitoring it. When the car is in production parts come in the door and get funnelled to spares or to new car production. If there is a quality problem with a part they see it right away on the production side and probably close the loop back to the OEM right away. Once the car goes out of production it is probably years from the time they get parts in the door to the time the get any feedback on quality.
So, basically I think even a factory new part is a bit of a crapshoot. Never mind a rebuilt or used one. And I am very slow to replace a known good part with something unknown.
While I am on a rant....Another thing is that these parts are not in isolation. The alternator, for example has the wires going to it, the belts around it, the hoses in the area, the oil pressure sender behind it etc. It often happens that when your are working on one thing, you will bump up against something next to it and cause damage. So you find that a little while after, say an alternator replacment, you find your self with a coolent leak or a flakey oil pressure signal. The better the feel your mechainc has for the fragility of old cars, the less of this sort of prolem you have. Greg is said to be very good, but I'll bet this sort of thing even happens to him.
As for carring around spares...I did this for years in my 914 days. I had a CV joint, and alternator, etc. Never had the part I needed at roadside, though. Since the 928 does not have a trunk seperate from the passenger compartment I would not even consider it unless I had a really good way to secure the parts. I'd think my chances of being smacked in the head by a loose alternator floating around the passenger compartment during a collision would be higher than having it fail and having it be a better and safer choice to fix it at road side than get the car towed back home.
AAA has a premium membership which provides for very good towing benifits, and is not too expensive. IMO this is a much better choice than fixing what ain't broke.
Some of my worst stranded-by-the-road episodes turned out the be caused by brand new parts I had just installed. I'm not sure about replacement auto parts in general, but for electronics parts there is a known failure curve with a big bulge in the first 100 hours or so, which ramps down afterwards and continues at a low and steady level for 20 years or so. The bulge even has a name - infant mortality. Again, I don't have data on auto parts, but my experiece says very strongly that they do follows the same curve. In fact it feels like it is quite a lot worse. If this is correct it might be explained because replacement parts (even new ones) have either been sitting on the shelf for 20 years or they were recently produced to 20 year old specs. I think the quality of newly produced parts goes down when the car goes out of production becaues you no longer really have the QA guys at the factory monitoring it. When the car is in production parts come in the door and get funnelled to spares or to new car production. If there is a quality problem with a part they see it right away on the production side and probably close the loop back to the OEM right away. Once the car goes out of production it is probably years from the time they get parts in the door to the time the get any feedback on quality.
So, basically I think even a factory new part is a bit of a crapshoot. Never mind a rebuilt or used one. And I am very slow to replace a known good part with something unknown.
While I am on a rant....Another thing is that these parts are not in isolation. The alternator, for example has the wires going to it, the belts around it, the hoses in the area, the oil pressure sender behind it etc. It often happens that when your are working on one thing, you will bump up against something next to it and cause damage. So you find that a little while after, say an alternator replacment, you find your self with a coolent leak or a flakey oil pressure signal. The better the feel your mechainc has for the fragility of old cars, the less of this sort of prolem you have. Greg is said to be very good, but I'll bet this sort of thing even happens to him.
As for carring around spares...I did this for years in my 914 days. I had a CV joint, and alternator, etc. Never had the part I needed at roadside, though. Since the 928 does not have a trunk seperate from the passenger compartment I would not even consider it unless I had a really good way to secure the parts. I'd think my chances of being smacked in the head by a loose alternator floating around the passenger compartment during a collision would be higher than having it fail and having it be a better and safer choice to fix it at road side than get the car towed back home.
AAA has a premium membership which provides for very good towing benifits, and is not too expensive. IMO this is a much better choice than fixing what ain't broke.
12-17-2007, 04:50 AM
#18
Three Wheelin'
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Bill's experience supports the anecdotal evidence anyway - the more you drive your 928, the more reliable it is.
