Engine Mount Bolt Shear Failure - info urgently required...

Hi Guys,

A cry from the tiny Island across the Pond here !

I'm faced with a £8k ($ 11,000) bill to fix my i3 after a bolt sheared 2 weeks ago. The reason I'm at this point is that literally 5 days after taking out Ext War with a 3rd party it failed so I can't claim as it was 2 days before my Healthcheck to validate the Ext War, so truly Sods Law as we say over here...

I saw Bob Wilsons extensive thread with excellent pictures of the work on his car (and will use some of the pics to check that the Nov 2015 upgrade was done despite being told by the Service Rep when I picked it up it hadn't been...) so I know some of you have been through this pain before so I have a question...

Does anyone know if there has been, either by recall or a change during the manufacturing cycle, a further upgrade on the bolts/mounts SINCE the Nov 2015 recall ?

Is yes, please let me have the evidence and dates of this asap.

If these are the correct bolts then frankly this is blatant design flaw and most people are sitting on a failure waiting to happen !

Any help greatly appreciated, best, K

At least in the USA, when the bolt was replaced, it was accompanied with a software update that tweaked the logic to avoid speeding up the wheel if it became unloaded. The problem is that with an electric motor, when you unload a wheel (going over a big enough bump), it can accelerate quite a bit and then when it hits the ground, exert a fairly significant impact load on the drivetrain. Without performing that software update, just changing the bolt to the newer one may not provide enough of a margin to prevent it from breaking the new one. Someone indicated that the mount was also reinforced, but not all vehicles got that.

Having seen my report, there isn't much I can add. However, the USA National Highway Traffic and Safety Administration listed two earlier bolt failures. I did not try to identify and contact the earlier owners. It may be possible to check the history of investigations to see if the original reports are still there with enough information.

Aluminum has a reputation for being less tolerant of stress over time compared to steel:
https://commons.wikimedia.org/wiki/File:Low_carbon_steel_and_Aluminium_Stress_vs._Strain_curve_E.png

It has been a long time since I studied mechanical engineering. I appreciate the lighter weight but you really need more mass to handle the stresses even from ordinary driving. In my case, it was driving too fast over speed bumps so the shocks would handle the impulse. Worse, I was steering the driver side wheels to take the gap so the passenger side rode the speed bump. Talk about one heck of a torque load!

Bob Wilson

Hi

I've had an i3 in the UK from new in 2014 until I got rid of it a couple of weeks ago.

There has been no engine mount bolt recall in the UK.

I wondered why not when I read about the US recall - but it definitely didn't happen her.

I had the mounting bolt fail three times on my I3 and then a final time after I had sold the car back to BMW. This was immediately after the car came back after a repair to the range extender (REX) that required the REX to be removed. No guesses as to root cause - most likely this happened with the engine work.

I understand the part that failed on the REX that stopped it working was minor.

Fortunately I was covered by BMW for years 1-3 and took out an extended warranty for year 4 when the further problems occurred.

I would raise this directly with BMW given the history with these failures.

I part exed my I3 against a one year old I3 with same spec other than the battery upgrade. Range & power usage dramatically improved. I also now have the rapid charger and that is likewise impressive.

It was a significant drop in value for my almost 4 year old 50,000 mile I3 but the cost to go back to a one year old I3 with just 5,000 miles was just £15k. Not too bad? So far no issues with the new I3 but this is still not a keeper after the BMW warranty expires?