Is it hooked up to the engine oil recirculation by any chance? I have not investigated it yet but I see a lot of engine oil near the fuel thermostat or beneath it. I just put a rag under it to mop it all up until I have the time to investigate/work on it. Where else in that area can leak engine oil?

It seems to happen to all my to be fixed up 300SDL.

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Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.