Mine is missing/broken. It is not covered under CPO. BMW claims if it is broken, it can not fail unless it was physically broken (i.e I must have done somehting to brake it). This seems to be a common occurence and some have said it is the first signs that my coolant expansion tank is about to leak. Has anyone had this issue fixed under warranty? Is there any TSB out on it?

 

Mine was missing too when I purchased the car. I had a leak in the resevoir tank so I replaced the entire tank. It comes with the float indicator and sensor as well. It's an easy DIY job. Takes about 30 to 45 min to do. Called the stealership to ask how much it would cost and they quoted $400 (parts/labor). Did it myself for $130 for parts only.

 

I waited and filled the tank to the float highest level. Bad as the front pipe under the Cal went and after I fixed that the tank blew a leak. My new tank took all of 10 minutes to install($140 at BMW) as it uses clips for the pipes and one electric connection. After filling the new tank I noticed that the level of fluid needed is way down when the float indicator shows full. hope this helps

 

go online and get the factory oem tank for $80