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So it sounds like its my turn.. the car has been ever so slightly whiny for a couple of weeks, but not at the point where a technician would definitely agree that something was up, So last night it decided to make it clear that it wasn't happy and now it has an unmistakeable whine on regen... car is going in to Pentagon Sheffield tomorrow for assessment. (Drive Leicester offered to look at it on 1st sept! I declined...)

I guess I'm going to be picking up fuel bills for the next couple of weeks... :(

I had an interesting chat to ex mechanic who had a collection of special bearings for use with Electric Motors, seems that its well known in bearing manufacturing that the harmonics of electric motors can cause unusual failures, so it might well be the case that the bearing GM used might have been ok in non motor applications.. That doesn't help me though..
 

· I'm not crazy, the attack has begun.
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I directed the tech at my slightly noisy bearing this service, and he said the bearing needs replacing. Funny, because it's been steady for me for 5k miles and it doesn't bother me. Might be the first time the tech has suggested a replacement before the owner!

I'm pretty sure I have an understanding of what is going on with this bearing, and it's not due to anything exceptional about the motor, but because it uses contact angle bearings but there is no 'strong' pre-load control and the bearing opens up too far under axial loads. It's OK for a while but once it starts opening up too much, it generates heat that can destroy the race and damage the bearing cages.

The cage failure is not a cause, it is a symptom. If it was a cause, why do the brass-caged bearings also fail?

This is my theory and may be wrong, but if correct it leads to a nasty conclusion - if the pre-load is poorly controlled, even after proper assembly, then it'll happen again and again. I can't see what controls pre-load, there is simply a shoulder on the outer transmission panel that apparently isn't even an interference fit, so I struggle to see how pre-load is maintained accurately.

This was a candidate for conical bearings, or even some sort of clever spherical bearing - looks to be the wrong bearing solution to the problem, IMHO.
 

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Do they? I hadn't heard of any.. my car is a very early version May 2012 almost certainly plastic..
I hadn't heard of the metal bearing cages failing either (though I haven't looked hard for examples)
 

· I'm not crazy, the attack has begun.
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41,188 Posts
When the repair is done, a metal caged bearing is used. It seems about a quarter of all attempted repairs fail a second time, ergo the brass bearing has failed too.

As mentioned, my interpretation of this is that they have not set the pre-load on the bearing properly, a second time, or that the bearing race moves and allows the rotating elements too much free-play. I don't believe the brass cage itself fails, but that the repeated noise is from the slack in the bearing.
 
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