Yep. Find a copper washer of the correct size.

 

No Part Num?

Thanks - I meant to add that there is no part number listed on realoem so not sure what size:

http://www.realoem.com/bmw/showparts.do?model=DN63&mospid=47588&btnr=11_1535&hg=11&fg=35

Washer is also absent from BMW of South Atlanta parts site:

http://parts.bmwofsouthatlanta.com/...9-E60-E61/2003/540iAutomatic/DOUBLE-TEMPERATURE-SWITCH/1276903/13621703993.html

Would you expect this?

 

What did you do with the washer that was on there? It can be reused.

The dealer will be the most likely place to get one. Otherwise, any copper washer of the correct size will do.

 

No washer on original

There was no original washer. The new water pump did not have any washers included but did have a small o-ring that looks to be close in size. I started poking around as part of the bleed, check for leaks process and noticed the gap and wondered if it was a potential problem.

I'll call the local dealer - thx

 

No washer required

FYI, I swung by the dealer yesterday as part of trip to HomeDepot to get wood to build ramps (forum links were great) and they confirmed what was online: no washer on the sensor so either it's undocumented in the BMW database, a Bentley doc error, or is associated with one of the other 5 series models.