𝗘𝗡𝗚𝗥.𝗠.𝗝.𝗠

 The Problem: Catastrophic Valve and Piston Failure (Cylinder Drop)

​Visual Diagnosis:

​Image 1 & 2 (Block/Piston): You have a shattered piston crown. The damage is not just melting; there is severe mechanical impact damage (peening) and debris. The center of the piston has disintegrated.

​Image 3 (Head): This is the "smoking gun." The cylinder head shows a missing valve head (likely the exhaust valve). The valve stem has snapped, and the valve head dropped into the combustion chamber.

​The Mechanism: The separated valve head was trapped between the piston and the cylinder head while the engine was running at speed. The piston hammered the loose valve repeatedly, shattering the piston crown, destroying the cylinder head face, and likely cracking the cylinder liner.

​2. Cause of Defect (Fault Tracing)

​According to Volvo Penta diagnostic logic, a failure of this specific nature (single cylinder, dropped valve) usually stems from one of two root paths:

​Primary Suspect: Mechanical Valve Failure (Fatigue or Adjustment)

​This is the most probable cause given the missing valve head.

​Valve Stem Fatigue: The valve stem may have snapped due to metal fatigue or a manufacturing defect, causing the head to drop.

​Incorrect Valve Clearance (Lash):

​Too Loose: Excessive clearance causes the rocker arm to "hammer" the valve stem tip, leading to stress fractures and eventual snapping.

​Too Tight: The valve doesn't close fully (riding the cam), causing it to overheat, weaken, and eventually burn or snap the head off.

​Valve Guide Wear: Worn guides allow the valve to wobble, stressing the stem until it snaps.

​Secondary Suspect: Thermal Failure (Injector Fault)

​While the mechanical damage is dominant, it is possible an injector failure started the chain reaction.

​Injector "Streaming": If the injector tip failed or stuck open, it would act like a cutting torch (thermal overload). This extreme heat can weaken the valve seats or the valve stem itself, causing the valve to drop and resulting in the mechanical chaos seen in the photos.

​3. Remedy (Repair Actions)

​This is a major failure requiring a "Power Unit" rebuild for that cylinder.

​Cylinder Head: The head in the image is likely non-repairable due to the severe impact damage on the fire deck. Replace the cylinder head (or the individual head unit).

​Cylinder Liner Kit: The piston and rings are destroyed. The liner is almost certainly scored or cracked. Replace the Cylinder Liner Kit (Piston, Liner, Rings, Wrist Pin).

​Connecting Rod: The force required to shatter a piston often bends the connecting rod. Inspect the rod for straightness or simply replace it to be safe.

​Bottom End Inspection: You must drop the oil pan.

​Debris: Check for metal fragments in the oil sump.

​Bearings: Inspect the rod bearings for impact damage (the hammering of the valve transmits shock to the bearings).

​Turbocharger Check: Debris from the shattered piston/valve often exits through the exhaust manifold and hits the turbo turbine wheel. Inspect the turbocharger hot side for impact damage.

​4. Prevention

​To prevent this from happening to the other cylinders:

​Valve Overhead Adjustment: strictly follow Volvo Penta’s service intervals for checking valve lash (clearance). This is the #1 defense against dropped valves.

​Injector Testing: Pull the remaining injectors and have them "pop tested" or bench tested to ensure they aren't leaking or streaming.

​Cooling System: Ensure the cooling passages are clean. Overheating makes valves and pistons brittle.

​Oil Analysis: Regular oil sampling can detect high metal content (wear metals) before a catastrophic failure occurs.