Hi all,

Any help would really be appreciated.
i decided to do preventative maintenance on my m2 N55.

Replaced pulleys, serpentine belt. torqued to spec. and after driving for about 10 minutes, i keep getting this Engine Overheating message.

I took it to BMW and they said that the belt looks correctly installed, but could potentially be a water pump malfunction? I’m not 100% sure.

Attached a pictures and links to videos of the car.
Any help is appreciated. Thanks!


https://files.fm/u/cjss7f6ucf

Did you bleed the cooling system after you completed your work?

assume you didn't touch the coolant system? could be a failed thermostat (locked closed) or water pump died (pump is electric). You could check if the water pump is working by doing a coolant system bleed process, you'll be able to hear the pump operating (either google or search the forum for the steps, it's pretty straight forward).

hi all,
thanks for the responses!
i did not touch the cooling system afterwards. my friend advised me to do a water pump bleed test?

thank you for that. i will give that a try this evening!

Cool, let us know.

i tried the following from the video.
all i heard was a small whining noise for a few seconds and then nothing.
i’m assuming that it’s a failed water pump?

Sounds like it

thank you. will be taking it to a shop tomorrow morning.

not sure if this helps, but i recorded the sound of the car. not even sure if this relates to the water pump or not.

https://files.fm/u/w97txf4bqx

That might be the throttle body defaulting to the closed position after turning off the car. It is normally open during driving, and closes when the car is turned off.

If you begin the bleed procedure, it takes about 10 minutes and you can hear the pump working and water flowing during that 10 minutes. Water flow will be on and off throughout the 10 minutes.

UPDATE.
Took my car to a shop and it was determined that it was a ground bolt for the water temp.
Per the shop:
"Note: Performed fault survey. No faults related to over heating issue. Checked and inspected cooling system components. Found ground wire for electric water pump assembly not connected due to broken bolt (no activation from water pump). Recommend install bolt for waterpump assembly and recheck. Installed new bolt for water pump ground wire. Function activated water pump assembly-Ok. Road tested vehicle. Ok."

Wow. I'd read about this issue in a FCP Euro blog post:
https://www.fcpeuro.com/blog/bmw-n55...lt-replacement

Figured it was just a way for them to pad out an order with a couple dollars for a bolt. But I guess it is a real thing. Just had never heard it anywhere else before.

yup. i read that haha. thank you !

Getting ready to replace the bolt on mine. Odd problem for sure!

I am amazed this doesn't have a sticky. I was replacing the coolant pump in my OG M2 and with everything was buttoned up, I discovered the sheared bolt and nearly crapped myself as I couldn't think of how in the hell I managed to knock anything in that area hard enough to shear a freaking bolt off at the head.

I replaced the pump anyway as it needed doing but had absolutely no idea at the time that this was actually a thing with these bolts. I ended up re-routing just nearby the pump in a different spot and the pump worked like normal.

Turns out these bolts just fail. And it's the aluminum in the bolt that ends up failing over time.

If you haven't done this on an N55 - DO IT before you're stranded in a very precarious position.

Can anyone advise if this water pump ground bolt can be accessed/changed without removing the stiffening plate?

I'd be hesitant to replace with a zinc plated bolt (corrosion), prefer either the BMW torx bolt option mentioned by FCP Euro or a s/steel bolt.

I don't really remember since I had my entire front end apart to do cooling mods when I did mine this year, but I think you can do it with the intercooler removed.


I used a grade 8.8 steel bolt with a super strong black anti-corrosion coating. These were the bolts that came with the turner motorsports carbon fiber corner braces and I just didn't use them and ended up with the stock bolts (I prefer the washers being attached to the bolt so I dont lose them). It's just a standard bolt with a 13 mm head, I paired that with another steel corrosion resistant washer (again came with my braces), and it worked fine.