I checked almost all my W126 fleet over the weekend and found some interesting info. It seems all have the same FD, Air Flow Housings (Meters) and EHA part numbers, which came as a surprize. What was even more interesting was the fact that there were additional numbers separate to the part numbers.... The cars I checked were all different specs:
500SEL LC import,
500SEL HC import,
560SEL HC import,
All had the same numbers:
FD 0438 101 018
AFM 0438 121 037
EHA 2437 020 007
The FDs had two additional stampings, the top one has 5 digits (to what is refers I have no idea). It is not the last part of the VIN, nor does it relate to any numbers on the data plate. Could it be the last 5 digits of the engine number? Something else I'll have to check... The bottom stamping has only 3 digits and seems to generally match that on the AFM AND the EHA (!) I can only deduce that this number refers to calibration between the parts. So if the numbers on your car are different, then the part/s have been changed at some point (and hopefully recalibrated).
What is very weird is the EHA (additional) number, since it doesn't appear to be stamped like the FD and AFM. It's a 3 digit number which is cast into the top of the housing below the part number.
On some of the engines all 3 digit numbers (FD, AFM and EHA) were the same. This would indicate factory (un-tampered) parts. Some had only the same FD and AFM 3 digit numbers which would perhaps indicate EHA replacement at some point (the 560SEL AUS was only one digit out FD 641 vs AFM 642, which could even be a typo). Note that I triple checked the numbers!
The 560SEL HC numbers were all different which would indicate some, if not all the parts have been replaced at some point. Interesting that it's been reported the HC engines had a different FD part number (0438 101 016) and if this is correct mine shouldn't be running at its full potential, yet it's running very well and has a significant bark. You can actually feel it in the accelerator pedal that it just wants to rev!
I can only conclude Bosch calibrated the FD and AFM according to the EHA cast number, however I'm curious about other opinions and suggestions....
1979-1991 280SE, 300SE, 300SEL, 380SE, 380SEL, 380SEC, 420SE, 420SEL, 420SEC, 500SE, 500SEL, 500SEC, 560SEL, 560SEC
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