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

......
......

The floor boards proper are steel, mild steel that's fairly easy to work with and weld .

Glued to them however, are the thick padded fiber sound deadening pads ~ you'll need to scrape those loose / up before you weld or you'll never get any seal in the floor .

I can't hear the dash noise but clearly you have an exhaust leak and I bet it's under the hood and drawing into the HVAC .

Look for fluffy dry black soot ~ that'll be the leak .

I bet no one told you you'd be a hands on Automotive Detective when you took on this project .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Haha.
Thanks! Where under the hood am i looking for this dry soot spot?

The entire exhaust system, begin where the exhaust manifold meets the cylinder head then look at every joint, there's lots of them .

Also closely inspect the flex pipe as it cracks .

It maybe not be obvious to you that the car will need to go up on a hoist for a full inspection .

Ask an independent muffler shop to have a look and give you a quote .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Also,
It occurred to me that i could cut out a lot of or all of the floor in my parts car as mostly one piece and swap over and weld / JP-Weld ????
That car's floor is in rather acceptable shape and i could mend one little spot, as opposed to this giant terrible floor in keeper car..

My one question about exhaust/bay/cabin leaks is this..
Would an exhaust leak in bay always cause the cabin to receive exhaust via air ducts? Or is it a double issue in that there is an exhaust leak in bay but also a leak in HVAC tubing as well...?

I guess I find it a little surprising that a properly working HVAC system would simply pull air directly from bay and treat its temperature but not filter it.

The Mercedes HVAC system always pulls in outside air from the vents below the windshield. That intake plenum is not perfectly sealed and leakage from underhood exhaust leaks will get in there. It doesn't matter how well the hood closes, if you have an under-hood exhaust leak, you WILL smell it in the car since the fumes will be getting sucked in by the HVAC system.

It shouldn't be too hard to find the leak. If you can smell it, you should be able to see it too. It may help to do your looking at night with a strong flashlight. You'll very clearly see the escaping gasses and smoke.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

I don't know about the advisability of JB Weld ~ I know it's good stuff but I'd rather have my torch guy weld it in after I'd cleaned up the edges of both car and replacement part, remembering to overlap by at least 1/4" ~ this small overlap is critical to safety and the repair holding .


You must also put the repair plate in from above, not offer it up from below, this creates better support .

You're taking the steep learning curve pretty well ~ keep at it .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

In both of my vehicles, the front seat floor boards have said thick pad glued to top of floor boards, but the rear floor boards are seemingly just one layer of something that i assume is steel, pictured here below...

It's QUITE flexible for being steel, which is what has been confusing. I'm thinking "wow this can be welded?" If i didn't ask anyone i would interpret this as being some sort of fancy plastic.

If i put a strong magnet to it, the kind that are very tiny circles but will not pull off of your refrigerator door without serious prying, it just barely stays on this piece of floorboard and if i shake it while sideways it will fall right off.

So i'm just looking to again confirm the best approach for joining new floorboard materials with old surrounding floorboard..

WELL WELL WELL! What do we have here??..
Seems PO or PM may have skimped during service or perhaps even this turbo was used for parts!
There is only ONE of the usually three braces that hold the turbo together, and thus there are only TWO of the usually six bolts. One of them is almost falling out!
Also plenty of soot around it. I'm going to go ahead and say this may be the reason the turbo whistle's so loudly. Clearly there is not a great seal going on here.
I've been getting around 9 to 9.5 PSI on the boost pressure readings during drives, so certainly it's only having a partial impact. On my previous (refurbed) turbo i was getting around 12. It was also not whistling.

I'm not 100% convinced this is the only source of exhaust getting into cabin, however. But maybe. It's a good bit further away from firewall than where i thought i've occasionally seen exhaust coming up from engine in the recent past. But that could have very well been just a breeze tossing it back.

I will need to either order the other two brackets or just pull off the brackets from my good turbo in other vehicle. Problem is i can't tell how easy it's going to be to get that one bolt back in place.

here we go.

I either have to replace the whole turbo with my other turbo, or i have to figure out a way to live with this one for a while and cut the exhaust situation somehow.

Turns out the reason all those bolts aren't there is because the threads in female sections are filled up with busted bolt halves. There's no way i'll ever get a good seal between two sections of turbo itself because there is only one bolt ever going to hold it.

Can i temporarily seal that edge of connection point with some sort of goop? Stuff that can withstand the high temperatures of a turbo? It's in place obviously, and mostly sealed, it just is about a 1/16th inch backed out around one side.

Swapping turbos is something i can do and i've done it already, but i'm weary of the bolts on this car more than other car. These ones all seem rather brittle. The thought of quickly attempting to remove the turbo from manifold without cracking those four big bolts sounds like a huge risk.. Even with preparing with rust penetrant for a couple days.

If i crack one, it could a week before i can drive while i struggle with the task of removing entire manifold drilling out those holes. But if i can plan for this project to take place something like thanksgiving week, maybe i can make due with some sort of sealant adhesive around this turbo juncture? Paste?

Part of me is glad i am going to forced to use my other turbo because it definitely seemed to be performing well and was refurb'd.

The fluffy exhaust is clearly visible on the lower part of your photo .

I'd say just replace the entire turbo with your spare assuming it spins freely by finger (! engine OFF !) and you never get thin blue smoke out the exhaust .

DO NOT swap the turbo without changing the O-rings and rubber oil return tube boot ! .

The stuff in your first photos is the non metallic insulation that was glued to the steel floor board ~ scrape it all up and see how much metal you have remaining .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

You mean the photo in post #1? That is a pic of the front passenger floorboard.
In both vehicles... The rear passenger floorboards have none of the insulation on top of it. It's just the thin firm steel.
In front, they do have insulation.
Are you suggesting scraping up both front insulations to check on the status of the floorboards under it?

NO .

I misread your message .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

It was not obvious to me! I will do this. What kind of rate should i be shopping around for for a full inspection and more importantly what are the segments of the underside of vehicle i should be prioritizing getting feedback about?

The flex coupler did look to be good as far as i could see but since i already put a new one on former vehicle i can pull that one over when i pull it's turbo over as well. Thing is, i had installed that without knowing that the engine mounts were causing the engine to tilt a bit, so after getting the flex coupler on (wasn't easy) it withstood a couple months of use under a little bit of awkward weight in one direction. It was only around 1/8" of pull to the side that the pipes misaligned by, but perhaps it's worth getting a new flex coupler just to get a truly fresh start there. I also put the engine through a long phase of bouncing around due to mounts going worse and worse until i replaced them.

And yes it spun freely. It is supposedly fully refurb'd and looked good as brand new when i got it. I'm planning to go through and double check everything on it though, looking for too much play in impeller.