I have soot coming into the rear bedroom. I have removed the rear fiberglass cap and found the cause. (See photos below) I am wondering if someone has a similar RV that can tell me what it looks like if you look up inside the rear engine access grill. There is a shelf that runs above the radiator and is attached to the rear wall. There is a few rubber sheets that form a shroud that essentially directs the air from the radiator out (or in) to the rear grill without spreading up and sideways behind the rear cap.
In mine, I think the previous owner attempted to stop the soot getting into the coach by spraying the expanding foam stuff up and around the rubber skirt and has essentially glued that rubber sheeting and the shelf to the rear fiberglass cap. I am having to bust out all that foam crap in order to free that shelf from the fiberglass so that I can reattach it to the back wall before fitting the cap over it. I am betting that a coach with a properly sealed back wall/roof/side wall will not have the foam crap and you'll be able to see that the shelf I am talking about is not attached to the rear cap, nor foamed to it either. Can someone confirm this for me?
Maybe any DP with the rear center radiator will be built similarly.
FWIW, below are the photos showing how the soot gets into the interior.
