This has been posted in two other sub-forums so no you're not seeing double or triple. Any a fellow E-Series friend/owner's '06 E350 has developed what resembles a leaky heater core smell. Pressure tests hold as they should and even close examination of the exposed heater core shows absolutely no leaks at all.

With the outer evaporator case removed for the inspection air cannot/does not flow through the core into the interior ducts---I notice the smell seems to be carried in the air stream the blower motor produces. This van has had varmint issues which might be unrelated but at this point I think cleaning the engine bay side of the heater intake including the blower motor wheel might get rid of the smell. This smell is much more noticeable when heat is required, A/C almost nothing. The heater core is amazingly clean and free of accumulated debris, cannot yet see the evaporator from all sides

Has anyone used or recommend a product for this? I've seen foaming-type cleaners you inject into the interior ducts that expands and supposedly cleans the inner surfaces, you simply suck it out with a vacuum cleaner after a while, the claim being any residual smells would be gone.

Anyway if anyone has any ideas please add them here. I'll be further disassembling the air flow components so access won't be an issue.

TIA

 

May, may not be of help but are you sure there isn't a small coolant leak elsewhere. Had a similar issue with another make and a slight smell would come in randomly. Turned out to be a small issue with the top radiator hose that would leave almost no trace of a leak.. The fan would drag in the odor.

 

Ya know that's an excellent idea or observation---something I'd maybe not considered before.

As you say even a small coolant leak produces that distinctive smell which is noticeable since its not something we normally smell.

I'll be looking for small coolant leaks but at this point it really looks as though something inside the plenum and evaporator/heater core box is causing this. Most likely I'll pull the blower motor and clean as much as I can using some sort of cleaning solution---thinking maybe Dawn detergent or similar.

Thanks Edkajo---appreciate the thought!