While replacing the water pump on my 83 300 d [284k] I broke the over flow nipple. I drilled and tapped the radiator to 1/4 coarse thread. [ at the break] then I cut the head off of a 1/4x1 1/2 bolt, drilled a hole thru it lengthwise, slipped a brass compression sleeve over the shoulder end and soldered it. Before screwing bolt into rad. it was coated with loctite. After 2500 miles no leaks.
Anyone tried this or have a better solution?