If your car is the 280CE with the 123 chassis'78-'81 model, replacement is fairly easy. It is mounted on front of the engine block and easy to get to.The hard part is getting those four 10mm screws off that holds the fan on.
The pump is what we "pros" call a four hole long nose pump. The part no. is 110 200 09 20. They cost about $36 and come with a gasket. I could be wrong and your car could take the short nose pump, so have engine no. at hand when you order the pump.
Bill lewallen Lexington,Ky. Home of Valvolene Oil-Maker of Mercedes Glysantin G-05 antifreeze....