w140 Potential Radiator/Cooling System Problem
 

I have a 93 MB300SD with 289,000 miles on it.

I just had it in to be checked (timing chain, etc.). The mechanic discovered a rust spot at the 90-degree turn in a 3/8-inch tube that comes out of the bottom of the radiator. It did not take much to cause the tube to leak at the bend.

If you have an older w140, it would be a good idea to check it.