With coolant leaking out the bottom weep hole, it is an indication the shaft seal is going on the pump. sounds like it is time to swap in a new one.
Here is what Pelican shows, I looked up 85 300D. part# 110-200-17-20
1985 Mercedes-Benz 300D Sedan - Water Pump, Thermostat & Hoses - Page 1
Be sure to replace the gasket.
I looked at a new one I have in the shop, and there are 2 weep holes, top and bottom. be careful removing the 4 small bolts holding the Fan Clutch to the Pump. they are 10mm and a bear to get to, and you don`t want to round them off.

then the fun of getting them back in.
Charlie