Are you sure it's coolant? Take a long cotton swab and clean out the dimples. Then you can feel the liquid to see if it is water-like (Coolant) or oil like (Hydro Fluid)

Re: daveycrockett
 

Same thing happened to me. My stealership wanted $800 too. My X5 4.8is expansion tank split along a corner and spewed coolant everywhere. Limped back home stopping every 4-5 mi to fill up the reservoir with water(I keep a gal of drinking H2O). Put the X5 in the garage. Went to realoem.com to reference the part no. and Googled the lowest price. Ordered the part ASAP $82.95. Two days shipping seems reasonable $14.95 Got a rental car for the next two days $29.95/day. Replaced it on day 3. Three hoses to disconnect and reconnect and 1 sensor. Time spent= 1/2hr. Back on the road.
Total cost:
$82.95+ $14.95 =Tank+Shipping
$72.88 =Rental
$170.78 =Total
saved $629.22= Priceless.

Replacing the tank is like a 10 min job, super super easy.

Agreed, unless the thermostat disintegrate on you when you pull the expansion tank off... That's what happened to me this weekend. Had to drill the thermostat out. In the process of taking the thermostat out the wall in which the thermostat goes into started to crack (it was very brittle) 135k miles, i don't think the thermostat or any coolant work has been done.
So now I am waiting on a new Mounting plate (Home Page > Search > 17111438819 > ES#37715 MOUNTING - 17111438819). I just need to be careful with the transmission oil cooler that plugs to this part.

I usually add some fine-ground black pepper to stop coolant leaking. It's like magic!

Nice!, I like that!

Just in case anyone is interested. I did it in 30 Mins.
http://www.xoutpost.com/miscellaneou...ement-diy.html