A bulldozer in the process of leveling the site, the diesel engine oil temperature gauge is always kept above 95 ℃, and the oil consumption is too much. The specific performance is that the exhaust pipe emits blue smoke when not accelerating, and thick black smoke when accelerating. Add the oil to the upper limit of the oil dipstick before working every morning, and the oil will drop to the lower limit of the oil dipstick the next morning. No oil leakage was found in the diesel engine.
After readjusting the valve clearance, remove the air filter and start the diesel engine, the exhaust emission of the exhaust pipe is not improved, which shows that the black smoke is not caused by insufficient fuel combustion.
When the cylinder head of the diesel engine was removed, it was found that incomplete combustion oil remained on the top of the piston, and there was a lot of carbon deposition in the combustion chamber. Turn the crankshaft to check that the cylinder wall is not seriously worn. Then, the oil pan was disassembled, the piston was disassembled, and the service condition of piston ring groove, piston skirt and piston ring was inspected. No abnormality was found.
Check the intake and exhaust mechanism of cylinder head. It is found that the inner diameter of some valve guides is larger than the specified size. When the valve moves up and down in the guide, it can be shaken slightly by hand. Through careful observation, it was found that the thread on the inner wall of the guide tube was seriously worn, and the clearance between the valve stem and the guide tube was too large.
The analysis shows that the clearance between the valve stem and the guide pipe is too large, which leads to the oil seeping into the combustion chamber along the clearance to participate in combustion. Due to the insufficient fuel combustion, the diesel engine overheats.
After all the valves and guide pipes of the diesel engine were renewed and assembled, the exhaust smoke of the exhaust pipe was normal and the oil consumption was normal.