Figured I'd put this out there for anyone who was interested in cleaning their engine grounds. I have a 2011 M56x but this should be the same for all M's of the same generation. Worst case, this should give you the general idea. No real benefit of doing this other than maybe making the electronics work slightly better due to less voltage irregularity, etc. although people claim that sometimes it will make the transmission, etc. work smoother/more precisely. Placebo told me the car felt good, but I also changed the oil and PCV valves just before this.

*Disclaimer* - I am not liable for anything you do to your car. This is just a basic walkthrough.

Task: Clean Engine Bay Grounds
Time: Took me about 35-40 minutes but I took my time and made sure stuff was perfect
Tools/Supplies Needed:

• Flat head screw driver
• 10mm Socket/Wrench
• 12mm Socket/Wrench
• Wire Brush, Pad or Wheel
• Safety goggles/glasses/shield if using air tools like I did

Process:

1) Open the hood. All of the grounding points that I could see easily were located on the driver side of the engine bay. Remove the large air intake scoop thing above the radiator using the screw driver to pop the pins. Then, remove the air intake tube (clamp at the throttle body and clamp at the air filter box) on the driver side and move it to the side to give yourself some more room. Note: This might not be completely necessary, but I had the intake tube moved to the side because just before doing this task I had changed the PCV valves...so not sure if you could clean the grounds as well as I did with the tube installed.

2) Here are the first set of four grounding points. The larger bolts are 12mm while the smaller ones are 10mm.



3) I removed the two 10mm bolts and this is what the wires looked like (left round terminal was cleaned before I remembered I didn't take a pic, it looked like the ones later in the guide before I cleaned it):



4) After cleaning them (and their mounting points on the block) with a wire wheel attachment on my air gun, this is the result. Mmmm, shiny!



5) I then removed the 12mm bigger bolts and cleaned up the mating surface and terminals here:



6) This is the final result of the first set of four:



7) I then moved to the other two grounding points I found which are located on the driver side strut tower...the bolts are also 10mm:



8) Here is the before:



9) And the after:




That's it...make sure they are all reinstalled properly and tightened and enjoy the placebo effect.

Below are some more diagrams from the FSM on the ground locations...showing the V6 and V8 locations...but then there is another image of a few more which I didn't see. When it gets warmer I might try to find those (I think the 2 on the strut tower are the two on the far right of the image).

V6:





V8:





Engine Room Harness:

Man I need you detail my engine bay...maybe at Carlyle this year we'll have a engine cleaning party with beer .

wideopn11 wrote:Man I need you detail my engine bay...maybe at Carlyle this year we'll have a engine cleaning party with beer .

Hah, I'll be on my honeymoon so no Carlisle for me this year.

As for detailing...general cleaning I use Purple Power or whatever it is called and dialute it slightly. Cover intakes if they are open, pre-soak engine (light rinse from the gun), spray it down with purple power and let it sit for 5 minutes, then take a brush and lightly agitate the purple power soaked engine, rinse off. Clean as a whistle.

If you're referring to things like ground wires, get yourself a dremmel with a wire wheel ...or an air tool like my dad has that I used lol. I try to clean every bolt I remove whenever I'm doing something with at least a wire brush and sometimes some anti-seize. That way if I end up keeping this car for who knows how long (very likely, love this car) I'll never have to struggle with seized nuts and bolts.

Ilya wrote: Before:




After:

Don't forget to clean the battery posts. Also clean the main ground strap that runs from the battery to the car body.

It is the black & yellow wire on the fender wall, attached directly to the battery.


Remove the 10mm bolt to clean both parts of this ground strap.

Thanks for sharing the photos IBC. I definitely didn't do everything and once winter is over I plan to do this again and do even more connections.

This is a great post and well needed. I haven't even given a thought to cleaning grounds. One can eat off my engine bay, but I didn't consider details like connections. I will be doing this when next I do my engine bay.

Ilya

Do you by chance still have these pics somewhere? I figure my grounds are what are causing my ecu to give me all these false values/random misfires....at least I hope it's that simple.

**Edit: Nevermind, for some reason they didn't show up on my iPad but work on my PC.

Shanehsmp wrote: ↑

Fri Feb 05, 2021 9:11 pm

Ilya

Do you by chance still have these pics somewhere? I figure my grounds are what are causing my ecu to give me all these false values/random misfires....at least I hope it's that simple.

**Edit: Nevermind, for some reason they didn't show up on my iPad but work on my PC.

Definitely give them a good cleaning and see if that improves. I need to do this again as it's been a while.

Awesome info, thank you. I have 2012 M56 with 68K miles, and start experiencing the same issues, random no start. Could not find much info on it on line. Was not sold that this is starter or alternator issue. So, long story short, I cleaned all the connection as you show on your pictures and it has been over one week, no issues and car noticeably starting better, sounds better. One thing I found that(picture one), on my car both wires were on the same bolt, I found extra bolt and connected where it is should be. There is reason for it, I believe.

Nikolai wrote: ↑

Sat Mar 18, 2023 7:13 pm

Awesome info, thank you. I have 2012 M56 with 68K miles, and start experiencing the same issues, random no start. Could not find much info on it on line. Was not sold that this is starter or alternator issue. So, long story short, I cleaned all the connection as you show on your pictures and it has been over one week, no issues and car noticeably starting better, sounds better. One thing I found that(picture one), on my car both wires were on the same bolt, I found extra bolt and connected where it is should be. There is reason for it, I believe.

Glad this helped you resolved your issue. That's what I love to hear!

Eeeehhh, issue got back today. Don't understand. Alternator charging, battery is new, ground connections are clean. Starter? Don't believe it, because it starts, just randomly wont. After trying 3-4 times it starts. Any ideas anyone?

No-starting randomly is exactly how most starters act when they begin to wear out. Either the contactor ring in the solenoid gets pitted, or the brushes wear down to the point where the springs get loose and can no longer force reliable contact with the armature. Keep hitting it with juice and at some point it arcs across the resistance and the starter spins. Further along you need to tap it with a hammer to wake it up. Then one day it stops spinning at all.

Just ordered new starter, Will update with results. Also, found discussion on line about possibly faulty/not compatible starters for M56, and recommendation to replace them. Unfortunately person did not posted more details. I wish they be more informative knowing how important that info is.