Is it necessary to replace all valves if one is damaged?
2 Answers
It is necessary to replace all valves if one is damaged. The working principle of valves is as follows: When the crankshaft rotates, it drives the piston to move up and down in the cylinder, which in turn drives the camshaft via a chain or belt. The cam lobes on the camshaft then press against the valves to control their opening and closing. Below are additional symptoms of valve leakage: 1. Valve burning leading to reduced sealing between the valve and valve seat. 2. Poor grinding of the valve sealing ring during maintenance. 3. Valve clearance adjusted too small, resulting in incomplete valve closure. 4. Foreign objects causing poor sealing when the valve is installed in the valve seat. 5. Carbon deposits on the conical surfaces of the valve and valve seat. 6. Pitting, scratches, stains, burns, or dents on the valve working surface. 7. Excessive runout of the valve and valve stem. 8. Excessive coaxiality deviation between the valve guide hole and seat hole.
I often encounter this issue when repairing cars: a valve is broken, but it's really not necessary to replace all of them. The key is to consider the engine's mileage and overall condition. If the car is relatively new, with less than 100,000 kilometers, and the valve wear is minimal, replacing just the single part is enough to save money and effort. On the other hand, for high-mileage vehicles, say over 150,000 kilometers, other valves might also be nearing failure, so replacing the entire set is more prudent to prevent imbalance-induced vibrations and reduce repeated repair costs. During the repair, don’t forget to check the valve springs and guides—if there are issues, address them together to avoid air leaks affecting performance. In the long run, a one-time investment can extend the engine's lifespan, but for a new car, it’s unnecessary waste. Always prioritize safety, and getting a detailed diagnosis from a professional shop is the most reliable approach.
