Please help me identify this part under the hood
 

Hi,

I recently bought a 1995 e320 wagon in need of a little mechanical TLC. I'm losing some coolant under the hood. I think it is coming from this part that I can't identify. Would you guys please help me ID it? It's the corroded barrel piece in the center of the frame in the last picture.

Thanks

13mm hex is the adjuster for the belt tensioner. it'll never leak coolant.

Its likely the water rpump that's leaking , it has a weap hole that leaks in that general area

Why is there tape on the radiator hose? Maybe that’s your leak

Thanks!

looks like a socket,still on the invert star bolt on thermostat housing.