I just changed the coolant/antifreeze in my 1984 300sd and while tightening the Plastic Radiator Drain Plug, the head broke off, due to the cold weather. I figure I have to drill out the the rest of the screw, but I was wondering what the radiator threads were made of, if drilling it out might damage the radiator itself. Any suuggestions?

I had a similar experience recently with an SUV.

I "carefully" drilled a small hole in the center, then used an EZ-Out to get the loosening process started. If you damage the threads, some sort of repair(depending on severity) will be required.

To me the trick here is accessibility....can you get a straight shot at it from underneath. If not, pull the radiator.

__________________
Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"

The plug at the bottom will come right out. Easiest way is to heat a SMALL slotted screwdriver red, and let it "melt" a slot in the CENTER of the blue screw. Good luck......

Thanks for the suggestions. Someone else suggested using a much smaller diameter screw die, which on backing it out will grab the plastic.

That same thing happened to me, but it was like 70F outside. I just released the lower radiator hose.

__________________
1992 Mercedes-Benz 400E
2002 Mercedes-Benz ML500