Coolant Leak: Need Help Identifying Part
 

I add coolant and the entire thing flushes out from under the car.

I figured out where it is leaking. Straight down right below where I am adding the coolant at the very bottom.

What is down there?

There is no low-coolant level warning on in my car.

EDIT:
http://img.photobucket.com/albums/v1...1092008079.jpg

That is where the leak was coming from. How do I go about putting that thing back? It was loose and had only one washer. What is that?

http://www.realoem.com/bmw/showparts...55&hg=11&fg=35 what hose is it coming from?

http://img.photobucket.com/albums/v109/Auction4B/01092008079.jpg

I found out where it is coming from. That.
It was loose! What is that for anyways?

Now how do I put it back together? It was attached with only one washer. I am assuming there are two?

link fixed.

My main concern is how do I put it back and make it tight.

that's the trans or PS cooler.

Fast4d is right on, thats the tranny cooler.

Replace the o-rings and reconnect that cooler, you are probably down SIGNIFICANTLY on trans fluid also.

thanks!

but why would the transmission fluid be low?

Because transmission fluid circulated into that cooler and then back to the transmission, if the lines to the transmission are disconnected the fluid will run out. From the photo it appears the trans lines are disconnected.

From the photo it appears the coolant runs into the trans cooler and not the trans fluid to the radiator. This would explain why when you fill up your radiator it empties itself right away. You will need to bolt the cooler in place with new Orings so that the coolant does not spill.