Daihatsu 6DK-20

Common issues

• Injector fouling and carbon build-up, leading to poor atomization and combustion.
• Exhaust valve wear, burning, and seat recession, particularly critical with HFO operation.
• Turbocharger fouling (compressor and turbine side) reducing efficiency and increasing exhaust back pressure.
• Cooling water leakage at cylinder head gaskets or internal cracks, often indicated by water in lube oil or exhaust.
• Piston ring wear and sticking, causing increased blow-by and lube oil consumption.
• Fuel pump plunger and barrel wear, affecting injection timing and fuel delivery consistency.
• Bearing wear (main and connecting rod) due to lube oil degradation or contamination.

Inspection checklist

• Visual inspection for any leaks (fuel, lube oil, cooling water, exhaust gas) around the engine block, cylinder heads, and piping.
• Check exhaust gas temperatures (EGT) per cylinder and at turbocharger inlet/outlet for consistency and abnormal deviations.
• Inspect cylinder head area for signs of cooling water leakage, valve rotator function (if fitted), and general cleanliness.
• Listen for abnormal noises from the engine, turbocharger, and fuel pumps (e.g., knocking, rattling, whistling).
• Verify lube oil pressure and temperature are within specified operating limits; check for signs of contamination.
• Inspect fuel injector high-pressure pipes for leaks and ensure leak-off lines are clear.
• Check turbocharger for excessive axial/radial play, unusual noise, and cleanliness of air filter and compressor casing.
• Monitor crankcase blow-by (visual observation or using a blow-by meter if available) for signs of piston ring wear.
• Review engine logbook for recent maintenance, running hours, fuel consumption trends, and lube oil analysis reports.

Service intervals

Typical wear limits

Ranges are typical for this design class. Always confirm against the manufacturer documentation for your serial number.

Critical spares

• Complete fuel injector or nozzle tips and associated seals.
• Exhaust valve spindle and seat ring (or complete valve assembly).
• Cylinder head gasket set (including valve cover and exhaust manifold gaskets).
• Turbocharger bearing cartridge or service kit (bearings, seals).
• Fuel filter elements (primary and secondary).
• Lube oil filter elements.
• Piston rings (at least one complete set per cylinder).
• High-pressure fuel pump plunger and barrel assembly.

Safety

• High-pressure fuel oil lines: Risk of spray fire in case of leakage. Ensure double-walled piping or proper shielding.
• Hot surfaces: Exhaust manifold, turbocharger, and associated piping can cause severe burns. Ensure insulation is intact.
• Rotating machinery: Flywheel, shaft couplings, and fan belts pose entanglement hazards. Ensure guards are in place.
• Pressurized systems: Starting air, cooling water, and fuel systems operate under pressure. Verify relief valves and system integrity.
• Crankcase explosion relief doors: Ensure clear space around doors and proper sealing to prevent crankcase explosions.

Class survey

Class surveyors will typically focus on the engine's overall condition, statutory compliance, and operational safety. Key checks include: review of engine logbooks for running hours, maintenance records, and lube oil analysis reports; verification of safety devices (overspeed trip, low lube oil pressure, high cooling water temperature alarms/trips); integrity of fuel oil system (leakage, screening, remote shut-off); condition of exhaust gas system (insulation, leaks); functionality of starting air system (pressure, relief valves, non-return valves); general engine cleanliness, absence of leaks, and abnormal vibrations or noises; integrity of engine foundation bolts; and confirmation of remote control and emergency stop functionalities.