This part is listed by BMW as BMW part number 17138093925 (17 13 8 093 925) and is described as the coolant expansion tank for the intake charged air cooling circuit on the S58 engine in the G87 M2, G80 M3 and G82 M4.
The recommended replacement interval is 100,000 miles on expansion tanks. That's because the plastic is known to get brittle and fragile with age, mileage, and thousands of heat cycles (cold to hot to cold again). Eventually the plastic gets so brittle cracks or holes form, and you'll either get a slow leak or a blow-out that leaves you on the side of the road, overheating. Replace this expansion tank preventatively and you can avoid this type of breakdown. This is a great part to replace while doing a cooling system flush or overhaul.
Cap sold separately. Please see below for BimmerWorld recommended related items.
This is a Genuine BMW expansion tank with a two year warranty. Buying a Genuine part will usually be more expensive than an OEM or aftermarket brand but you are assured that it meets BMW's designs for fitment, performance, and longevity. It will also be the very latest design, incorporating any updates or revisions that an aftermarket brand typically will ignore.
BMW Fitments:
2 Series
G87 (2023-) > M2 (2023+)
3 Series
G80 (2021-) > M3 (2021-)
G80 (2021-) > M3 Competition RWD (2021-)
G80 (2021-) > M3 xDrive Competition (2021-)
4 Series
G82 / G83 (2021-) > M4 (2021-)
G82 / G83 (2021-) > M4 CSL
G82 / G83 (2021-) > M4 Competition RWD (2021-)
G82 / G83 (2021-) > M4 xDrive Competition (2021-)