I have a 2005 S40 that developed a wet carpet on the passenger side. I noticed that the coolant was low and after I pulled the carpet away from the floor, I noticed the sound proofing under the what I gather is the heater core was wet also. Does anyone have any experince in replacing this item. I found a used core on Ebay for 80 bucks but used.

 

You sure it's coolant under the carpet and not water?

 

Water, as opposed to coolant, being a sign of either the evaporator drain loose/clogged or the sunroof drain clogged.

 

Yep. Both way more common. I've never done a P1 heater core and have seen dozens of clogged sunroof drains and multiple evaporator drains.