Some common problems with the Passat diesel engine include failed head gaskets, check engine light and fuel leaks. Each problem may require extensive repair procedures completed by professionals.
The head gasket is responsible for sealing the surfaces between the cylinder head and block. When these gaskets fail, the engine loses compression and will overheat. Overheating can cause additional problems and, if not repaired, result in engine failure. In order to replace the head gasket on the engine, the coolant needs to be drained, several of the engine components removed along with the entire cylinder head. While the head is removed, it will also need to be properly machined. The machining will check for imperfections, and completely flatten the surface so it can seal the new gasket properly.
The check engine light is generally related to electrical issues stemming from the wire harness, which can be checked by the Volkswagen dealership.
The fuel filter on the Passat diesel engine also had sealing issues. This causes the fuel to leak out while the engine is running, which creates a risk for fire. Due to this being a manufacturing defect, Volkswagen issued a recall in 2012. This recall requires Volkswagen dealerships to replace the fuel filter free of charge.