[QUOTE]Originally posted by Michael Stoic
[B]
The RV is located in the engine compartment, inner left fender,
on my car (89 300SE) - within easy reach, but I know that at least one more vent or purge valve is somewhere near the rear axle. Anyone know of a procedure for testing the fuel tank vent system on a W126?

Hello Michael Stoic,

I believe your 300SE is close to my 260E 1988, I changed both valves you mentioned, the one in the engine compartment and the one on the right rear side and it goes to the tank. It is connected with two times 5cm of fuel hoses.
Very easy job and the part is very cheap.