There is also the option of a BMW coolant expansion reservoir part #17111712641 that has a low coolant sensor installed. You have to mod it for the V8's Throttle Body Heater hose.

 

have you modded one or seen it done? probably pretty simple, but i'm having a hard time visualizing it.

 

A “T” fitting is needed to add the throttle body heater hose to the coolant system.

 

Also note that the BMW expansion tank has the hose fitting on the bottom in 90 degrees as the original has it 45 degrees.
It will fit and work, but will slightly kink the hose a bit more.

Sorry, don't have any better pic online handy than this


I haven't installed this yet on my V8 because the throttle body heater missing fitting.
Still on the edge on "deleting" the tbh, but we do have actual winters here, so....
On my TD5 I have that tank installed and working.

 

Fitted aluminum part.

So far thrilled.