1. Valve ablation. Mainly is the exhaust valve material is poor or the exhaust temperature is too high, cause valve cone ablation, or because of valve seat deformation, bow from the cone ablation. In addition, the valve clearance is too small, or the valve spring is too soft, make 4 leak and valve ablation.
2. The valve is broken. Most are the result of poor manufacturing quality. A severed valve head is dangerous to a diesel engine. If the valve head falls onto the top of the piston, it will break the piston and the cylinder head. When the valve clearance is too small or cylinder, there is a foreign body, the top bad valve head, or even make it broken.
3. The valve seat comes off. It's a dangerous malfunction. The valve seat ring as a whole after the fall of a strange sound, if the debris fell on the top of the piston, will cause damage to the piston and cylinder.
4. Bend the valve lever. The main valve clearance is not appropriate and was bent.
5. The valve stem is worn. Mainly due to poor lubrication. The valve is killed in the catheter. Most of the valve stem and catheter clearance is too small, the oil is too dirty, valve stem deformation and other reasons, so that the valve stuck in the catheter and unable to move