What are the causes of valve burning?
3 Answers
The causes of valve burning are: 1. Simultaneous increase in sealing surface temperature and local pressure between the valve and seat leading to distortion and carbon deposits; 2. Improper valve clearance adjustment or excessive wear; 3. Dirty gasoline, poor operating environment, prolonged high temperatures; 4. Poor valve material or excessively high exhaust temperature. The valve consists of a valve head and stem, and its function is specifically responsible for introducing air into the engine and expelling the exhaust gases after combustion. Usually, car owners can use the "hanging bottle" method for cleaning. The hanging bottle is similar to the form of a hospital IV bottle. The cleaning solution is injected into the valve, resulting in better cleaning effects without the need to disassemble the car engine, making it an effective cleaning method.
I've been driving for over twenty years and have encountered several instances of burnt valves, mostly caused by an overheated engine. Issues like a malfunctioning cooling system, a non-functioning fan, or leaking coolant can cause temperatures around the valves to skyrocket, leading to burning. Fuel quality is also a critical factor—using low-quality gasoline or excessive additives can result in incomplete combustion, accumulating heat around the valves and eventually causing erosion. Additionally, during long-distance driving with high engine loads, such as climbing hills or speeding on highways, the valves endure extra stress and are prone to damage. I once witnessed a friend’s car suddenly burn out due to severe carbon buildup on the valves from neglected regular maintenance, which prevented proper heat dissipation. For prevention, don’t overlook coolant checks—top it up with fresh fluid every six months. Always refuel at reputable stations, and avoid prolonged overheating of the engine. Drive smoothly and avoid constantly flooring the accelerator, as that puts excessive strain on the valves.
A while ago, my car had valve issues, and after a long investigation, I summarized several common causes: First, fuel problems—if using a lean fuel mixture (e.g., high air ratio), combustion temperatures become excessively high, causing the valve metal to fail and burn. Second, engine aging—over time, valve seals degrade, allowing hot exhaust gases to leak in and repeatedly heat the valves. Third, poor driving habits, such as frequent idling in city traffic or aggressive throttle use on mountain roads, leading to large engine temperature fluctuations. During my own inspection, I found the cooling fan was stuck and couldn’t assist, causing localized overheating and melting of the valve edges. After repairs, I adjusted some habits: regularly cleaning the air filter to ensure smooth airflow and prevent carbon buildup; changing engine oil more frequently to maintain lubrication and reduce friction heat. Daily driving now includes paying close attention to the dashboard coolant temperature—if it rises, I slow down or stop to cool off. Small maintenance steps cost little but save big on major repairs.
