coolant leak on 1990 Mercedes-Benz 300E

I have a 1990 mercedes 300E. 150,000 miles. 300ci 6 cyclinder. There is a coolant leak on the drivers side coming down the side of the motor. I cant see exactly where it starts because the intake manifold is in the way. I can see it coming from above the motor block freeze plug, not the plug itself. The car runs normal. No smoke or coolant coming from the exhaust. Oil is ok. It does not overheat. The temp gauge is normal.

The water pump has a hole in it where when it starts to leak you will never see it except on the side of the motor. Not to hard to replace but you need some dexterity and a hex/ allen ended socket to remove. I bought a few at Advance auto. 6, 7, 8mm
2 more answers
Most likely the O ring btween the block and the pump I just replaced mine.
Did you ever find out what was causing this coolant leak?