What are the causes of valve leakage?
2 Answers
Here are the causes of valve leakage: 1. Wear, burning, spots or depressions, and carbon deposits on the working slope of the valve and valve seat ring. 2. Excessive clearance between the valve stem and valve guide, causing the valve stem to wobble or bend, or the valve head to tilt, resulting in incomplete valve closure. 3. Weakened or lost elasticity of the valve spring or a broken spring can also prevent the valve from tightly fitting with the valve seat. 4. Small valve clearance causes the valve stem to expand when heated, and the tappet and rocker arm push the valve open, preventing it from fully closing and leading to leakage. 5. Prolonged operation of the engine at high speed and temperature weakens the valve spring tension, preventing the valve head from pressing tightly against the valve seat. 6. Failure of the decompression mechanism, causing the valve to close incompletely.
When I used to repair engines, I often encountered valve leakage issues. There are several reasons: the valve itself may wear out over time and fail to seal properly; valve springs can lose tension due to aging or fatigue, preventing tight closure; carbon buildup around the valve can hinder proper closing; or engine overheating may cause valve deformation and leakage. These issues can lead to reduced engine power, a significant increase in fuel consumption, and in severe cases, black smoke from the exhaust. It's advisable to regularly check valve clearance, use high-quality oil to minimize wear, and avoid letting the engine temperature get too high while driving. If you notice poor acceleration or unusual noises, visit a professional repair shop promptly to prevent minor issues from turning into major repairs. At home, you can simply observe the exhaust condition to assist with preliminary diagnosis, but avoid disassembling the engine yourself—improper handling could make things worse.
