What is the reason for the lack of cylinder head oil pressure in Ningdong 8300?
2 Answers
Ningdong 8300's lack of cylinder head oil pressure may be due to a two-stroke engine, primarily caused by wear of the cylinder block, piston, piston rings, leakage of the crankshaft oil seal, reed valve, and cylinder gasket. Below are the specific reasons: Four-stroke engine: Mainly due to valve leakage, excessive clearance between the piston, piston rings, and cylinder block, cylinder gasket leakage, or the use of non-standard or mismatched parts such as pistons, leading to a reduced compression ratio and decreased pressure. Mainly due to valve leakage, excessive clearance between the piston, piston rings, and cylinder block, cylinder gasket leakage, or the use of non-standard or mismatched parts such as pistons, leading to a reduced compression ratio and decreased pressure. Solutions for insufficient cylinder pressure: First, check the sealing of the valves and valve seats, and grind or replace them if necessary. Check the opening and wear of the piston rings, and adjust or replace the piston rings as needed.
I've dealt with this issue quite often at the shipyard. When large diesel engines like the Ningdong 8300 lose oil pressure in the cylinder head section, it's mostly due to a blockage in the lubrication path. The oil pump draws oil from the oil pan, passes it through the cooler and filter, then routes it through the main oil gallery to various branches. The problem occurs when the branch leading to the cylinder head gets clogged. Common causes include a stuck pressure-regulating spring in the oil distribution valve or sludge buildup on the valve spool—especially since these engines operate at nearly 90°C oil temperature during continuous operation, and low-quality oil tends to form gum deposits. Last time I disassembled one, I found the oil hole under the rocker arm shaft support half-blocked by sealant. Another easily overlooked point: the check valve in the connecting pipeline between the main oil gallery and the cylinder head oil passage—if installed backward, it can completely cut off the flow. A quick check by feeling the oil pipe temperature helps: the branch pipe without oil pressure will definitely feel colder than normal ones.
