How to Determine Engine Piston-to-Head Contact?
2 Answers
When there is an issue with the connection between the piston and connecting rod, such as excessive clearance, it can cause the piston to exceed its normal operating trajectory, directly contacting the cylinder head. If the timing belt has exceeded its service life or the tension adjustment device fails, the coordination between the timing belt and timing pulley becomes loose. Possible causes include seized valve stems, broken intake/exhaust springs, valves falling into the cylinder, or incorrect piston size during repairs, as well as excessively thick connecting rod bearings or shims.
I've driven trucks for over twenty years and witnessed several instances of valve collision. When the engine suddenly makes loud metallic clanging noises, like a hammer striking inside, and the vehicle loses power when you step on the gas, it's most likely a valve collision. Once, while driving, my engine suddenly stalled, and the starter couldn't even turn it over. After towing it to the repair shop and opening it up, sure enough, the piston had bent the valve. My advice is, if you hear any abnormal noises, don't push your luck—pull over immediately. Also, pay regular attention to the timing belt; if it's worn out, replace it promptly—if it snaps, it will definitely cause valve collision. And change the engine oil frequently; if the oil pump fails, the piston can overheat, expand, and collide with the valve.
