I did the wiping -> turn on/off -> wiping as described in my previous post:

ATF slow leak above pan (right rear): easy to repair?

ATF is coming out there.

Due to the leak there, the dealer did the following repair last October.

The invoice states "replace governor pressure valve replaced".
000-304-28-90 magneto supp
000-304-27-90 coil
115-304-01-60 seal.accel c
001-997-35-48 seal ring, tr
008-997-30-48 seal ring, vl
008-997-31-48 seal ring, vl

The dealer said that the leak looked like from the part 123 277 0103 in the picture, but it was from elsewhere.

I asked why the invoice mentions "governor pressure valve" while the parts list does not contain it. The dealer answered, "The magneto supp and coil that was replaced are part of what is called in Mercedes a Governor pressure valve switch. In modern days, it is also called solenoid."

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1992 300D 2.5 turbo diesel. 319 k miles.
124.128 chassis, 602.962 engine, 722.418 tranny.