In today’s post I will try to explain the engine mount problem and how to solve it. Once forever.

Here’s what happens.

The Motor Mount/Bracket Problem

Affected vehicles: BMW I01 i3 BEV and i3 REX produced from October 2013 up to November 2015. 

During the hard acceleration, an extreme shock to the driveline, such as a quick loss of traction, causes this failure. For example, if you get the rear axle airborne while accelerating while keeping your foot on the accelerator pedal, the electric motor will quickly achieve very high speeds without any load.

The impact force from the drivetrain may damage the motor mount bolt (it’s the left side mount in a BEV and both sides in REX) or the left plastic mount bracket when the tires contact the ground while the motor is freewheeling at such a high speed.

If this happens, it’s obviously terrible, but if you keep driving, you risk serious damage to high-voltage components (EME, KLE). 

Depending on the situation, damage may also occur to other components of the driveline and motor electronics.

So, to avoid costly repair, check your engine mounts. 

Here’s how to check the mounts:

So, if your i3 has the old plastic engine bracket installed, do not hesitate to upgrade motor mounts. 

Engine/Motor Bracket And Mounts Replacement

A permanent solution is the replacement of both engine mounts and the left engine bracket with redesigned parts and software updates (I’ll cover it later).  And here’s the tricky part: if your i3 isn’t covered by warranty or service action, the BMW dealer will quote you some crazy amount of money. Mostly for labor.  

Because of the strict BMW Service procedures, the technician is required to remove the complete engine assembly out of the car and then replace the motor mount bracket. 

We don’t need to discuss the BMW’s official repair procedure, but I’ve changed a few electric motor brackets in less than 2 hours without removing the engine. The only challenge I faced the first time I did it was losing the three 16mm bolts holding the bracket to the engine. 

I quickly constructed the tool so I can unbolt these three bolts, and the rest was easy. 

Note!

When the mount bolt, the mount, or the bracket is damaged, they can cause damage to other components. So, before concluding the work, make sure to check the following:

• Check the high-voltage cable under the drive shaft sleeve for damage and replace it if necessary.
• Examine the bracing strut for paintwork damage and apply corrosion protection to any sections of the paintwork that may be damaged.
• Examine the battery voltage line near the iso-fix strip for damage and, if necessary, replace it.
• Check all visible electrical connectors for damage and, if necessary, repair them. 
• Check the inner drive shaft CV boots. 

When replacing the mounts, you should also consider replacing the middle one. 

If you decide to do it yourself, please check this forum thread below. Keep in mind that you don’t need to drill (and shouldn’t) the holes in the rear subframe. I really can’t justify why this guy did it.

https://www.mybmwi3.com/forum/viewtopic.php?t=17251

The bolts (1) holding the electric motor bracket shown on the motor removed.

To access these bolts you’ll need a tool like one of these:

Matco Tools Serpentine Belt Tool MSBT15

I did my own by just welding the ⅜ 16mm socket to a 19mm wrench and it did the job just fine. 

Note! This guide is missing the most important part when working on electric vehicles: Disconnect the 12V battery negative lead before any work is done! The 12V battery also powers the high-voltage battery electronics.

THIS IS NOT BMW APPROVED PROCEDURE! 

The complete guide for both the BEV and REX I’ve found over at the mybmwi3.com forum:

https://mega.nz/file/fEo3UIJJ#NBqXt5zJgbQsJvq4nodSTNnQ1XlTGq-Uq_yprT-qXfs

The Software Update

Besides the hardware upgrade, BMW also addressed this issue via the software. The problem with the old software version is too slow reaction of the traction control. When this happens with the combustion engine it’s not a big deal. But the electric motor will spin almost instantly – up to 11k RPM – before traction control kicks in, and cut the power. 

From the I-Level 15-11-502 software update, this issue is addressed and the motor electronics will cut the power of the electric motor more rapidly to reduce the motor speed. 

I’ve heard a few complaints about the reduced power output, or reduced regenerative brake energy, but these complaints are just fantasy. With the software upgrade, you won’t lose any electric motor performance. 

The software update procedure for the BMW i3 is exactly the same as for any BMW F-Series. If you do it yourself, the best option is to use E-Sys. If you have access to the BMW ISTA application, you’ll need the Programming Data and it will work just fine. 

Conclusion

This is the real problem and you never know what driving situations you may face in the future. So for any 2016 or older BMW i3 owner, I strongly advise you to check the motor mounts and replace them with the upgraded set. And don’t forget the software update!