I have a 240D, 1983 Mercedees.
At about 250K miles, I also had an anifreeze drip coming from the water pump and eventually realize, it was coming out of a drip hole that was on the bottom side of the pump. This hole is made so that when the seal on the water pump shaft (that spins where the blade is on the inside to rotate the antifreeze) it drips out of the drip hole.
Get prices on the water pump. I think Mercedees wanted like $300 and got mine at Karr parts for like $75.
Replacement is very easy. Just loosen up fan belt. Take the bolts out that hold the fan on. Pull back and forth hard to get it offf. Don't forget to buy a water pump gasket if it calls for it.
Hope it helps.