What are the causes of car valve leakage?
4 Answers
Reasons for car valve leakage: 1. Wear, burning, spots or depressions, and carbon deposits on the working inclined surface of the valve and valve seat ring; 2. Excessive clearance between the valve stem and valve guide, shaking of the valve stem or bending of the valve stem, and tilting of the valve head, resulting in incomplete valve closure; 3. Weakening or loss of elasticity of the valve spring or spring breakage can also prevent tight fitting between the valve and valve seat; 4. Small valve clearance, after the valve stem expands due to heat, the tappet and rocker arm push open the valve, preventing the valve from fully closing and causing leakage. The valve is an important component of the engine, and its function is to specifically deliver air into the engine and discharge the exhaust gas after combustion.
I remember when I drove that old truck, I also encountered the issue of valve leakage. The vehicle ran as if it was gasping for air, especially fuel-consuming and slow in acceleration. The main reasons were poor daily driving habits, often driving short distances in the city, stopping before the engine warmed up, leading to carbon buildup in the valve gaps, making them not close tightly. Also, as the vehicle aged, the valve stems wore out, the sealing rings became brittle with age, and the springs lost their strength, unable to prevent gas leakage. Additionally, using low-quality gasoline with many impurities could accelerate these problems. Now I know, it's necessary to regularly clean the engine to prevent such small issues from becoming major problems. Replacing the sealing rings or grinding the valve seats can make a big difference. Safety first.
My new car was only three years old when it suddenly started shaking violently on the highway last month, and I felt like I lost half the power. Later, after an inspection, they said it was due to valve leakage—so frustrating! The mechanic said the main cause was likely material aging, like how I didn’t change the engine oil on time, causing the engine to overheat and warp the valves, cracking the sealing surface and letting air leak out. Also, during cold weather, uneven thermal expansion and contraction widened the gaps, making the leakage worse. So now, I make sure to get maintenance every 5,000 kilometers, checking whether the valve components are worn or loose to avoid this kind of issue again—it affects driving safety and burns through money.
As an enthusiast who enjoys tinkering with cars, I've disassembled several engines and understand how valve leakage occurs. The most common cause is seal failure, such as aging or cracked seals, or misalignment during installation where the valve doesn't sit properly on the seat, allowing gases to escape through gaps. Poor combustion can also lead to carbon buildup clogging the gaps and worsening leakage. During repairs, it's essential to use the correct tools to avoid bending the valve stem. A simple DIY check involves using a compressor to detect leakage points—if it's too severe, replace the components. Remember, avoid aggressive driving to prevent overheating and accelerating the issue.
