What is this part? Heating system?
 

So my car started to overheat in traffic the other day and before I could pull over it popped and steam started spewing out of the engine bay. Found the culprit but I'm not sure what to call it and what exactly I have to replace on this sucker. Here are some pics. It is located at the back right of the engine bay while looking at it from the front of the car.

http://forums.pelicanparts.com/uploa...1389050741.jpg


http://forums.pelicanparts.com/uploa...1389050868.jpg


http://forums.pelicanparts.com/uploa...1389050878.jpg

Thanks in advance!

Andy

Possibly the circulation control valve...look into a Haynes manual.

which model, year and engine?
Anyway, looks like the auxiliary water pump under the heater valves, for example in case it is a E34, the part number is here

1 Additional water pump 64 11 8 390 090
Water valve/Water hose BMW 5' E34, 525i (M50)