freightliner 04 century class under truck ?

This might sound dumb and sorry but some things im just not good at getting technical about, but I have an 04 century class company truck know. Ok there's this radiator looking thing under the bunk area on the outside see im looking at what that part is. Is it bunk heater or oil cooler? Anyhow I ask cause it smokes and bad, so im looking for info so i can point it out to part switcher guy at the yard you know. Thanks for any info thart is posted.

 

ok that sounds about right thanks. First company got to get frame straitened out, thats a whole nother story but its how i found the truck. And trust me this truck has a story to tell just haven't gotten it out of it yet. Thanks for the replies.