SMG II - MLR Engineering Accumulator

[oceansize]

The environment where the pump lives is harsh which impacts longevity/durability; however, a properly functioning system can run at high temps without failure from my personal experience.

Correct, but at some point the o-rings and seals fail, at which time you only have repair, buy rebuilt, buy new options. Nothing lasts forever without maintenance, that was my point. The SMG pump will fail at some point in a long term owners lifetime. Whether the motor, accumulator, seals, o-rings, sensor, etc.

In the past, particularly on the old m3forum where misinformation about the SMG ran high, people would have heat issues and say well I'm going to relocate to solve that, or do the resistor mod (dumb). Relocation won't solve heat issues if items within or on the pump require maintenance.

[bmrdvr]

Hi There - I'm currently on this same boat but i have not had enough time to troubleshoot to the extent that i wanted to, couple of things in my current environment, i have two fully functional pumps, both of which have been replaced (internal oil pump seals, solenoid seals, etc) - One pump has a new accumulator bought from BMW, the other pump has the original accumulator that came used from when i bought the pump - the pump currently in the car is the one with the old accumulator, this one is giving me the COG while hot - I then swapped the accumulator for the new one, this helped tremendously but the issue returned (it did however, make it more difficult to overheat) - My assumption here is that i did not bleed enough the system when i swapped the acc and air might causing this COG

Note: The original pump of the car never gave me any issues, even after replacing seals, etc. Even replaced the accumulator with a bmw one as preventative, no issues in any temp spectrum.
Note2: I couldn't bleed the system properly due to the lack of my 10A power supply that i lent and the car is no longer a daily and i have not had the time continue the troubleshooting.

I hope this helps.

Ok so you've got a pump assembly with new seals, new o-rings on the solenoids and a new BMW accumulator and you'll occasionally get a cog when hot?

1. Did you buy that accumulator and/or you know its history as a new part?
2. Do you have the specific codes it was throwing? In my case it was for the pump running too much i.e. the pressure wasn't holding and the motor was constantly running.
3. Have you replaced the temp sensors?

Honestly, I doubt its a bleed issue. The system will self-bleed over time so if you got it to run without going through the procedure then it was likely good enough. I've bled SMG systems by just running through the gear changes and clutch actuations a few times using INPA with success (vs the actual procedure in ISTA). Also, the only time you're going to need a power supply is when you're programming modules. For basic troubleshooting and activating components like this, you can run that thing on the battery and be fine. It's when you're writing data to the modules where there is a high current draw that the power supply is required so it doesn't fail in the middle of writing the data.

FWIW: BMW want 100A power supply to write program modules. I think the blower motor and maybe a few other things would pull more than 10A. The small wires and low voltage mean there is a lot of current (amps) in these systems and the need for really robust power supplies.

[bmrdvr]

Correct, but at some point the o-rings and seals fail, at which time you only have repair, buy rebuilt, buy new options. Nothing lasts forever without maintenance, that was my point. The SMG pump will fail at some point in a long term owners lifetime. Whether the motor, accumulator, seals, o-rings, sensor, etc.

100% agree. For my issue, I do not believe the pump seals or solenoid o-rings to be the problem (I've replaced them all as well as the brushed DC motor). The only thing that changed was the accumulator. It worked fine on it's first long trip in April 2024 but the second long trip it struggled in moderate ambient temps. At this point I'm just going to buy a BMW accumulator next year and see how it runs next summer. I'm ok throwing parts at it mainly because: at some point none of these parts will be available so it will be worth having spares. I hope it's not the MLR unit because when cold, it does pass the ISTA test just fine but who knows. I think what pisses me off more than buying a second accumulator is all the damn clamps I've gone through on the throttle bodies lol