Trap Oxidizer Skullduggery?

Exactly where is/was a 300SDL's trap oxidizer located, and what does it look like?
After purchasing my SDL two weeks ago, I called service department of
the local Mercedes dealership to ask them to consult the database and find out whether the car had ever undergone the removal of its trap oxidizer under recall. Surprisingly, it hadn't. That was strange for such an old car, I thought, but the service rep said there were still a few stragglers out there. He also said that the recall had expired a couple of years previously (news to me), but that the dealership still honored it.
I took the car in today to have the work done. When I got it back late this afternoon, I looked under the hood to see what was different. The piece that I thought had to have been the trap oxidizer -- a foil-covered horizontal cylinder about 15 inches long and maybe 3-4 inches in diameter, oriented fore and aft to the right of the valve cover and at about the same level -- was still in place.
The only component of the exhaust system that was obviously new was a length of exhaust pipe well downstream of the turbocharger, the segment slanting downward aft of the turbo and leveling out underneath the floor- pan before connecting to the front end of the muffler.
Now as I understand it, the problem with the trap oxidizer is that the porcelain grid inside the thing might eventually come apart and enter the hot section of the turbo, causing damage. If that's the case, then it makes no sense to replace any exhaust-system components *downstream* of the turbo as part of this recall.
It's also my understanding that this recall involves not just removing the trap oxidizer and replacing it with either an oxygen catalyst or a section of straight pipe (I've heard both versions; with my '85 300D, it was the former), but also removing and inspecting the turbocharger for damage, and if any is found, replacing the turbo.
The mounting hardware on the turbocharger had obviously not been removed and replaced; it was still covered with the standard surface corrosion that's commonly found on older exhaust-system components. The same was true of the aforementioned cylinder to the right of the valve cover.
The work order reads "Replace oxidizer trap for diesels only. See bulletin 96-1121." Followed by: "Replacement of oxidizing trap for diesels only. Trap replaced as per bulletin."
But the only parts that are listed on my receipt are as follows:
    126-490-13-20    exhaust pipe     603-140-03-03    pipe elbow     202-492-01-81    coupling rin [sic]     126-492-01-82    ring, exhaust     107-492-00-82    damping pad     107-492-00-82    damping pad [listed twice for some reason]
There's nothing in there that would appear to be a replacement for the trap oxidizer. "Exhaust pipe" has to refer to the long section under- neath the car.
Is it possible that the dealership didn't bother pulling the trap oxidizer, but simply installed a new section of exhaust pipe in an easy-to-reach area so that something new and shiny would be visible in the engine bay to make it *look like* they did what I asked them to do?
Before anyone mentions black helicopters or tinfoil beanies, I can come up with a reason why this might be so: because they recall expired a couple of years ago, and despite what the service rep said about still honoring it, the dealership may have felt it wasn't worth their trouble -- especially if they were no longer going to be reimbursed by DBAG -- and didn't want to piss off a customer by coming out and saying so.
Thanks, Geoff Miller
'87 300SDL '91 300D 2.5 '82 300CD '85 300D
--
"Am I crazy, or is it hot in here?" -- Charles Manson


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I understand your puzzlement. I've seen lots of pictures of the '86 & '87 engine with and without the large can next to the valve cover - the modified cars being without it.
As to why THIS work was done and NOT the can removed? I'd suspect that (i) no dealer does gratis work (at least of this magnitude), (ii) THIS job may still be covered by MBUSA reimbursement whereas the can's removal is not. So they did something!
Ask how much they'd charge to replace the can with a straight pipe. Can't be very much - and then your car is fixed.
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So that can *is* the trap oxidizer, then, as I suspected?
And am I correct that inspecting (and if necessary, replacing) the turbocharger is/was part of the deal?

What puzzles me is that the dealership nevertheless incurred expense by doing work that was unnecessary. It seems to me that if remiburse- ment were an issue, the sensible approach would've been for them to have told me at the outset that the recall had expired and would no longer be honored, and let it go at that. Instead unnecessary time and money was spent on my car, and they even gave me the free use of a loaner vehicle.

I'll consider it. Thanks.
Geoff
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What puzzles me is that the dealership nevertheless incurred expense by doing work that was unnecessary. It seems to me that if remiburse- ment were an issue, the sensible approach would've been for them to have told me at the outset that the recall had expired and would no longer be honored, and let it go at that. Instead unnecessary time and money was spent on my car, and they even gave me the free use of a loaner vehicle.
Not unnecessary if MBUSA was paying!
Others here may have more detailed information about the can and turbocharger. As I understand, the point of the replacement was to prevent broken ceramic pieces from destroying the turbo.
Another point. This is a fine engine but it cannot be overheated!!! Overheating will blow the headgasket (that's the good news) and may also crack the aluminum head, particularly at #4 and #5 cylinders - where the can is located. So take good care of its cooling system and take it easy on long grades.
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Thanks. I really appreciate your input.
I don't mean to be pedantic, but I've got to ask: What's meant by "overheating," in terms of this particular engine? Is it enough simply to keep the temp needle south of the red line, or are slightly lower temps (say, 90-100C) risky as well? Can the effects of repeated, relatively high (but below redline) engine temperatures be cumulative?
The reason I ask is that one route that I often take home from work is a fairly relentless uphill run into the mountains. If that's a risky proposition with this car, then I can easily use Route B.
Incidentally, I've noticed that the engine temperature in the SDL, like that in my 300D 2.5, is a lot more sensitive to both engine load and ambient temperature than with other cars I've owned (including my two diesel W123s). It's as though Mercedes designed in just enough cooling capacity and no more. (The SDL had a new radiator not all that long ago, so I doubt that's the reason.)
Both run fairly cool on the freeway with ambient temps in the 70s or 80s (say, engine temps of 80-90C), but climb quickly on uphill grades and in hot weather. I've been considering having the thermostat replaced on the 2.5 when it goes in for major service later this month as a precaution.
Geoff
--
"Am I crazy, or is it hot in here?" -- Charles Manson


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Overheating = boiling.
It's as though Mercedes designed in just enough cooling capacity and no more.
You got it right. You're lucky that a new radiator was recently installed.
You're well aware of the engine's temperature so you shouldn't have a problem. I wrote that for someone who charges long hills on hot days with the A/C on full blast to know that such demands will do significant damage to these engines.
The engine should run at 80 degrees C. and will rise with loads but keep it out of the RED!
Good luck with it.
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The trap oxidizer is much thicker than that one you descrbie, probably 6-7 inches in diameter, and the consturction looks just like catalyst converter, except shorter. Notice the space between the valve cover and the side wall that has aluminum shield? The oxidizer pretty much occupies that entire space. The one you have, 3-4 inches in diameter, with shining foil, is the replacement.
I am sure about this because my 300SDL did not get the recall done when I bought it 3 years ago. MB dealer replaced the oxidizer (and turbo) later without me saying much. They did not mention any expiration.
Geoff Miller wrote:

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