What causes the cylinder head noise in Passat B5?
2 Answers
The causes of cylinder head noise in Passat B5 include piston slap noise, valve noise, and timing gear noise. The details are as follows: Piston slap noise: A dull, rhythmic knocking sound can be heard in the upper-middle part of the engine, which is more distinct during cold starts and idle operation, and significantly diminishes or disappears when the engine reaches normal temperature. Valve noise: A continuous and rhythmic sound is emitted from the top of the engine during operation, most noticeable and clear at idle, and less apparent at high speeds. Timing gear noise: The engine's timing gear may be located at the front or rear of the engine, producing a chaotic noise with distinct metal clashing sounds. In severe cases, the engine timing may become misaligned, preventing startup. Disabling a single cylinder's fuel or ignition has no effect on this noise.
I've worked on quite a few Passat B5 models before. Cylinder head noise is mostly caused by failing gasket seals or issues with the hydraulic lifters. Aged gaskets leaking oil can make the valve noise louder, sounding like a ticking noise; if the hydraulic lifters get stuck or the oil pressure is unstable, it can also cause abnormal noises, especially more noticeable when the engine is warm. Another possibility is improperly adjusted valve clearance, which naturally increases over years of wear and tear, requiring disassembly for inspection. I recommend first checking the engine temperature, as overheating can easily damage components, necessitating a cooling system check. If such issues aren't addressed promptly, at best, fuel consumption increases, and at worst, the engine can suffer from cylinder scoring, affecting the overall vehicle safety. It's best to quickly visit a professional shop for diagnosis and replacement of critical components.
