2002 Mercedes Benz ML500 Weld or Replace Engine Mount

It depends on what part you're referring to. Is it an engine mount that is bolted to the engine and the body? Those are replaced. If it's an ear bolted to the engine, those are also replaced. If it's an ear cast as part of the engine block, the repair depends on whether it's cast iron or aluminum. Aluminum can be welded but it requires special equipment, and the area of the joint must be perfectly clean just prior to the welding operation. Welding cast iron is tricky because it's porous and will crack or shatter from the sudden temperature change. The parts need to be preheated for a long time with an acetylene torch to raise the temperature a lot before the parts are welded.