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