BMW N20 & N26 Expansion Tank

BMW N20 & N26 Expansion Tank

The expansion tank for the BMW N20 and N26 turbocharged straight 4 engines looks like a golf ball or radome.

I think it looks pretty neat with the white round plastic over the E90's black square expansion tank. The reservoir in the picture below is from a F30 328i.

 

The part number for the OEM expansion tank is (17-13-7-642-158). Mike Miller recommends changing the expansion tank at 90,000 miles.