I don't know whether it is a serious problem or not. My SDL is leaking/dripping coolant from the expansion tank, the one behind the passenger fender. I have never seen what is behind the fender but it seems to have a drain pipe leading to the wheel well. The car never over heat and it hoovers around 80-85 degree C even it a hot day. I do not need to add coolant as there is no warning light in dash. The car starts first time every times and drives well. No smoke at idle or when running. Is it a serious problem like a blown gasket coming? I overfilled the radiator? Or the radiator cap cover is not to spec?

Any help is appreciated.

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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.