Your head gasket is leaking MOTOR oil into the coolant and does that probably at a return line of the motoroil system.
I had the same problem with my 300SL-24 (104 engine) and just finished putting the head back on.

Gary, you are talking about a head gasket leak that blows compression air from the cylinders in the coolant system/water lines of the head...that is a different leak and can cause more damage as an oil leak.

greetingz,

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1990 300SL-24
1993 C250D with a minor 600+k kilometer
www.MBenzNL.com(the Netherlands)