Interesting, well it sure feels like it's just some sort of fiber board. It is all easy to bend by hand, not even just in the rusty sections.

My main reason for attacking this was because i have been getting some exhaust fumes in the cabin air and this is definitley a major reason my lungs have been irritated. I need to address this asap obviously.

I had assumed that this would be the main leak of fumes, and after sealing this whole floor up very thoroughly with thick clear plastic and with gorilla tape at every edge on hard surface along the way, i turned on the car and still have the same amount of exhaust in the cabin.

But now that i had this floor sealed i could at least do a controlled experiment to trace other culprits, and my second guess was the answer.. It's coming from the vents when any air is turned on. I've suspected this but the floor leaks were so glaring that i assumed they were more likely.

I did a test where i cleared out the air for several minutes with the car off and doors wide open, then i closed the doors/windows and say in the car off to make sure the air was clear, then i turned the engine on but kept the heat/air OFF and those vents turned shut. Came back 5 minutes later and hopped inside and it smelled normal just as it did before running car. Then i turned on the heat and opened the vents and left the car like this for another 5 minutes. Came back and sure enough the cabin was smelling strongly of exhaust and was tough on the lungs.

Below is a video of a strange sound that i get when the air/heat is turned OFF. With the engine off, this doesn't occur even with i turn the heat/air ON. This sound is heat OFF and engine running. Then when i turn the heat on (engine still on) this sound completely stops. This is why i have been running some sort of air treatment the whole time i've been driving, because this sound when it's turned off is so annoying and loud.

What could this be, and could this have something to do with exhaust getting into the cabin?

In the video i twist the vents shut and you can tell that the sound is in the dash and perhaps related directly to the vent lines internally. This video doesn't show me turning the heat ON, but if it did the rattling sound would just completely stop.

http://media.spacecasetapeecho.com/ventrattle.1.mov

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