What are the causes of valve leakage?
2 Answers
Valve leakage is caused by: 1. Damage or detachment of the valve lock pin and lock piece, resulting in incomplete valve closure; 2. Excessive clearance between the valve stem and the guide, causing the valve stem to wobble; 3. Wear or erosion of the working conical surface between the valve and its seat ring, leading to valve leakage; 4. Bending or breaking of the valve stem, or tilting of the valve head, causing the valve to lose its sealing function; 5. Weakening or breaking of the valve spring, resulting in insufficient seating force during valve closure. Valves, also known as air valves, are divided into intake valves and exhaust valves. They serve as crucial control components in the internal combustion engine's cycle of intake, compression, power, and exhaust, and are installed within the engine cylinder block.
I've seen quite a few cases of valve leakage. The main reasons are erosion or deformation after prolonged high-temperature operation, where the edges wear out and create gaps, preventing a tight seal. Another common cause is wear on the valve seat, leading to poor sealing—like our old family car, which leaked due to carbon deposits stuck between the valve and seat. Additionally, weak valve springs can cause trouble; a friend's car had unstable idle speed for this reason. Sometimes, it's an assembly issue—either the clearance is too tight or the installation angle is off. For maintenance, it's important to clean carbon deposits promptly, check the valve stem seal's integrity, and use high-quality engine oil to reduce wear. This issue can hurt engine performance and increase fuel consumption.
