I've had this on both of my M103 engines. My guess is that oil pools up at the valve guides back there and get's a small leak in one of the valves, most likely intake. This never seemed to cause any noticable problems like smoking or oil consumption however it should be fixed eventually. It's probobly time to replace the valve stem seals. Replacing seals is easy on the M103 engine, I can personally do the job myself in 2.5 hours.

The M103 is a great engine and along with the 126 body, a very reliable package. I would highly recommend keeping that car with only 55K miles on it.

I would drop in some sea foam, fill the tank, change the oil and filter, change the coolant (Red! not the green stuff!!) Fog the cylenders and change the spark plugs, remember to gap them!

From here i'd drive the car for at least 100 miles and see how it runs.

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Current Stable:
01 ML55 AMG
92 500E (a few mods)
87 300E (lots of mods)
00 Chevy 3500HD Diesel Box Truck
68 18' Donzi Marine
06 GT i-Drive7 1.0 Mountain Bike (with GPS!)

PREVIOUSLY OWNED:83 300SD, 87 420SEL, 88 420SEL, 90 420SEL, 86 560SEL, 86 190E 2.3-16V AMG, 94 E320