What Causes Valve Noise?
2 Answers
Valve noise can be caused by the following faults: 1. Wear or improper adjustment of the valve stem end and adjusting screw or rocker arm, resulting in excessive valve clearance, causing collision between the side-mounted valve tappet end and the adjusting screw, or impact between the rocker arm head of the overhead valve and the valve end. 2. Excessive wear of the cam, causing the tappet to jump during operation. 3. Detachment of the valve spring seat. 4. Loosening of the valve tappet fixing nut or uneven end face of the adjusting bolt. 5. Excessive carbon buildup in the valve guide, causing the valve to stick. Here are the methods to diagnose valve noise: 1. Listen at the valve cover. If the noise changes with engine speed but remains unaffected by engine temperature changes or ignition cut-off tests, it can be identified as valve noise. 2. Run the engine at idle speed and insert a feeler gauge into the gap between the valve end and the tappet. If the noise weakens or disappears when inserting the gauge into a particular valve clearance, it indicates excessive clearance in that valve. If the noise reduces but does not disappear after inserting the gauge, use a screwdriver to pry the valve stem. If the noise disappears, it confirms that the noise is caused by excessive wear between the valve stem and the guide.
I've been driving for over a decade, and valve noise is a common issue. The most frequent cause is excessive valve clearance - you hear a tapping sound when accelerating, usually due to uneven camshaft wear or hydraulic lifter problems. If engine oil isn't changed on time, sludge buildup makes the lifters less responsive, amplifying the noise. Some neglect maintenance, allowing dust to accumulate in the valves, which eventually causes significant noise. I must warn everyone not to ignore such abnormal sounds. Prolonged neglect can seriously damage the engine, ranging from increased fuel consumption to cylinder scoring or even complete failure. Getting the clearance checked or performing lubrication cleaning at a repair shop typically costs around $10-20, providing both peace of mind and safety.
