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EVO final drive flange recall
- Thread starter mindsoma
- Start date
pglaves
#13338
I am not a metalurgist and I am not a machinist but I do not believe there is a single photogragh in this thread (or anywhere else that I have seen) that looks like a crack across the flange was caused by over tightening a non-tapered fastener into the flange. Tightening a steel fastener that is not tapered too tightly into a threaded piece of aluminum usually distorts or strips the threads or crushes the face of the aluminum at the threaded hole. How it forces a crack the length of the threads escapes me. It sounds like a fabricated excuse made up by a criminal defense attorney to me. But remember, I am neither a machinist, nor a metalurgist, nor an attorney of any kind, let alone a criminal defense attorney or any other type of criminal attorney for that matter.
Gotta agree there Paul, typically a stripped out aluminum thread when over tightened using a steel bolt.
Way too many rotor mounts cracked to be a operator error, and this is only wheel mount I have seen cracked.
Good article in the ON about relatively simple repair, however I will let BMW pay for the whole operation...no bill to pay
Way too many rotor mounts cracked to be a operator error, and this is only wheel mount I have seen cracked.
Good article in the ON about relatively simple repair, however I will let BMW pay for the whole operation...no bill to pay
Remember that the mother ship attributed the failures of the plastic fuel pump inlet fittings to "overtightening" as well. Sure seems to be a rash of overtightening going around.Gotta agree there Paul, typically a stripped out aluminum thread when over tightened using a steel bolt.
Way too many rotor mounts cracked to be a operator error, and this is only wheel mount I have seen cracked.
Good article in the ON about relatively simple repair, however I will let BMW pay for the whole operation...no bill to pay
JayJay
pglaves
#13338
In that case they were right because the intern specified a tapered fitting to be screwed into a plastic piece. The taper wedged the plastic outward leading to cracking. But the wheel flange issue is not due to tapered capscrews/
Paul, I agree, but ... the female threads of that fitting were in a relatively thin-walled protrusion above the plate of the pump mounting flange. Had the walls of that particular piece been thicker, or shaped differently, or made of a different material, I don't think that we would have had the issue even with modest overtightening. I've seen some photos where that cracking extended through the fitting and down into the plate itself. There are tapered plastic fittings used widely, and successfully, in many pressure applications. There's nothing inherently wrong with a tapered fitting in plastic, but it has to be executed well.
I'm not a metallurgist, nor am I a plastics engineer, but I did spend quite a bit of my career designing and building hydraulic systems. And as an engineer myself, I really don't like to second-guess another engineer's design decisions. But in the case of the outlet fitting on the fuel pump housing, I think they fell short. Clearly there was a disconnect between the engineer's expectations of how it would be assembled, and what actually happened - the assembly appeared to be intolerant of real-world conditions. The failure was more than "overtightening", it was a non-robust design as well.
Having said that, I still haven't heard a credible explanation of why the fuel strips seem to keep failing.
JayJay
pglaves
#13338
Having said that, I still haven't heard a credible explanation of why the fuel strips seem to keep failing.
JayJay
I think they are inherently unreliable in fuel that changes temperature by 100 degrees or so every now and then. They tried it in 1983-1985 and went back to a float in 1986. But that engineer retired so the institutional knowledge of all the reasons not to do it left, so some youngster decided to do it again.. That's what I think anyway. I could be proven wrong but it hasn't happened on this issue yet.
deilenberger
A bozo on the bus
Paul, I just want to know if you stayed at a Holiday Inn Express last night..
BTW - my new steel flange seems quite robust... one thought I had on the cracks appearing on the rotor mounting holes is - the rotor is solidly fixed to the mount on the rear. The read disks on the Hexheads was known to get quite hot (finger burning hot - DAMHIK) due to dragging brake pads (probably caused by inadequately lubed sliding-pins on the single-piston sliding caliper.) The disk would expand outwards becoming larger in diameter. That means there would be an outward force on the rotor bolts, and so far - all the failure pics I've seen (and my failure) have the crack on the most outward part of the flange mount for the rotor. It cracks in the direction it would if the bolt was being forced outward from the center.
Just speculation on my part. It might have just been a poorly executed bad design. That happens.
