What Causes Valve Leakage?
3 Answers
Valve leakage can be caused by the following reasons: 1. Wear and burning of the valve and valve seat working surfaces, leading to spots, pits, or carbon deposits. 2. Excessive clearance between the valve stem and the valve guide sleeve, causing the valve stem to wobble. 3. Weakening or loss of elasticity in the valve spring, or spring breakage. 4. Factors such as excessively small valve clearance. Additional related information is as follows: 1. The car valve, also known as the throttle, is responsible for introducing fuel into the engine and expelling exhaust gases. Traditional engines have only one intake valve and one exhaust valve per cylinder. This design is relatively simple, cost-effective, easy to maintain, and performs well at low speeds. However, its drawback is difficulty in increasing power, especially due to low charging efficiency and weaker performance at high speeds. 2. To improve intake and exhaust efficiency, multi-valve technology is now commonly used, with each cylinder typically having four valves (some designs feature three or five valves per cylinder, following the same principle, such as in the Audi A6 engine). A four-cylinder engine thus has a total of 16 valves, often denoted as "16V" in car specifications, indicating the engine has 16 valves in total.
Valve leakage is a common issue with multiple causes. The most frequent is wear on the valve sealing surface - over time, the contact between the valve and seat becomes uneven, allowing compression pressure to escape through gaps, reducing engine efficiency. Carbon buildup is another culprit, particularly when gasoline or oil combustion residues accumulate on the valve, preventing proper closure. Spring fatigue leading to insufficient tension and unstable valve movement can also cause problems. Other potential causes include deformation from excessive heat and improper installation with incorrect clearance adjustments. Having repaired many vehicles, I've observed that leakage can lead to rough idling, skyrocketing fuel consumption, and even cylinder scoring failures. Therefore, I recommend performing a compression test or endoscopic inspection when symptoms appear - early repairs can save significant costs.
Valve leakage directly threatens driving safety, with main causes including poor valve sealing, carbon buildup blockage, and spring failure. Leakage reduces cylinder pressure, weakens engine power, causes sluggish acceleration, and may even lead to stalling in severe cases, which is particularly dangerous during uphill climbs or high-speed driving. Additionally, engine overheating can cause valve deformation, worsening leakage and potentially damaging the entire system in a vicious cycle. I once witnessed a friend's car requiring a major engine overhaul due to neglected minor leaks, resulting in unnecessary expenses. During inspections, pay attention to abnormal engine noises and unusual exhaust smells, and promptly seek professional diagnosis to ensure safe driving.
