MAN L27/38 Diesel Engine — Cylinder Head Removal
- Removal: High-pressure fuel lines, starting air lines, cooling water lines, exhaust lines, sensors, and indicator valves.
- Remove the cylinder head bolt protective covers; install the hydraulic tensioners; loosen the nuts using a symmetrical, crosswise pattern.
- Typical specifications for MAN 27/38 diesel engines: Oil pressure of 1200 bar.
- Using a specialized lifting tool, carefully lift out the cylinder head; remove the cylinder head gasket vertically (replace with a new one).
MAN L27/38 Diesel Engine — Piston and Connecting Rod Removal
- Bar the engine over to the vicinity of Top Dead Center (TDC), and clean the lifting hole on the piston crown.
- Open the crankcase inspection doors; remove the connecting rod big-end bearing cap and bearing shells, and apply matching marks.
- Attach the specialized piston lifting tool, and slowly and vertically hoist out the piston-connecting rod assembly.
- Place the assembly onto a specialized support stand to protect the piston, piston rings, bearing shells, and piston rod.
MAN L27/38 Diesel Engine — Cylinder Liner Removal
- Remove cylinder liner cooling water inlet and outlet pipes; perform temperature measurement and lubrication.
- Using specialized tools, smoothly hoist out the cylinder liner; inspect the water jacket, sealing rings, and check for corrosion.
- Clean the cylinder block bore; replace the sealing rings.
Cleaning and Inspection (Critical)
1) Cylinder Head
- Clean carbon deposits; inspect valve holes and cooling water chamber for cracks/corrosion.
- Disassemble and inspect intake/exhaust valves, valve seats, pressure test (5 kg), measure guide pipes, springs, and valve handles.
- Grind sealing surfaces; perform a sealing test; flatness ≤ 0.05 mm.
2) Piston and Rings
- Clean top, ring grooves, and cooling chamber carbon deposits (do not use wire brushes).
- Measure: piston diameter, taper, ovality; ring groove height, wear.
- Measure piston rings: end clearance, side clearance, elasticity; replace immediately if cracked/chipped.
- Inspect piston pins, pin holes, and retaining rings; measure clearances.
- Clean inner wall; grind off upper bosses (to prevent cylinder scoring).
- Measure inner diameter, roundness, cylindricity; check for scoring, cracks, and cavitation.
- Minor scratches, oilstone polishing; replacement for defects exceeding standards
4) Connecting rod and bearings
- Check connecting rod for bending/twisting; flaw detection
- Bearings: alloy spalling, burning, scratches; measure bearing clearance
- Connecting rod bolts: cracks, elongation, threads; must be replaced (high cycle)
