What Causes Valve Noise?
3 Answers
Valve noise can be attributed to the following reasons: 1. Wear or improper adjustment of the valve stem end and adjusting screw or rocker arm, resulting in excessive valve clearance. This causes the side-mounted valve tappet end to collide with the adjusting screw or the rocker arm head of the overhead valve to impact 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 tappet fixing nut or uneven end surface 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 near 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 confirmed as valve noise. 2. Run the engine at idle 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 gap, it indicates excessive clearance in that valve. If the noise reduces but does not disappear, use a screwdriver to pry the valve stem. If the noise is eliminated, it confirms excessive wear between the valve stem and the guide.
My old Jeep used to make a constant clicking sound, like a small hammer tapping. Upon inspection, it turned out the valve clearance had increased, mainly due to prolonged use causing part wear. When the engine runs, the opening and closing of valves require precise clearance. If it's too loose, the camshaft will produce knocking sounds. Additionally, dirty or insufficient engine oil can accelerate noise. I forgot to change the oil on time, which made the sound more noticeable. Ignoring such noises may, in the long run, damage the valve seats or the engine internals, leading to repairs costing several thousand dollars. If you hear similar sounds, don't panic immediately. Ask a car-savvy friend to listen and focus on checking the clearance and oil level. Don't slack on regular maintenance—check the oil every 5,000 kilometers, which usually helps prevent issues.
Working in an auto repair shop for a long time, encountering valve noise issues is quite common. The most frequent causes are improperly adjusted valve clearances or worn valve guides, which hinder smooth movement and create noise. Additionally, engine oil with too low viscosity or degraded lubrication is a major factor—I've seen many cars develop louder noises due to the use of cheap oil. During diagnosis, don't just rely on listening; it's best to use a stethoscope to pinpoint the exact location. The solution is straightforward: first, measure and adjust the clearances. If that doesn't work, check the oil condition and try replacing it with fresh oil. Small issues left unattended can lead to chain reactions, such as burning out valve seats, doubling repair costs. Remind yourself to routinely check oil pressure and engine cleanliness—regular maintenance can prevent most of these troubles.
