I have seen many early 300E and 300D (W124) MBs with a broken upper radiator neck. The replacement radiator has a metal insert inside the hose connector. If your radiator does not have the metal insert, replace the radiator or take it to a radiator shop to replace the tanks. Whenever I buy a used W124 MB, that is the first thing I check after the engine is at room temperature the first time in my garage.

David