Information on diagnostics

Piston damage and causes

Piston seizure or piston broken? What was the cause of the damage? We will help you to correctly diagnose damage in day-to-day repair shop activities and prevent expensive consequential damage. 

Piston crown damage

Seizure due to overheating (mainly piston crown)

  • Overheating due to combustion defaults
  • Bent/blocked oil injection jet
  • Installation of incorrect pistons
  • Malfunctions in the cooling system
  • Clearance restriction in the upper sliding surface area



Impact marks

  • Piston protrusion too great
  • Excessive remachining of the cylinder head sealing surface
  • Incorrect valve recess
  • Incorrect cylinder head gasket
  • Carbon deposits on the piston crown
  • Insufficient valve clearance
  • Incorrect valve timing caused by incorrect adjustment or a slipped toothed belt

Fused/melted off material

  • Faulty injection nozzles
  • Incorrect quantity of injected fuel
  • Incorrect injection point
  • Insufficient compression
  • Ignition delay
  • Oscillating injection lines



Cracks in the crown and crown bowl

  • Faulty or incorrect injection nozzle
  • Incorrect injection point
  • Incorrect quantity of injected fuel
  • Insufficient compression
  • Lack of piston cooling
  • Installation of pistons with incorrect bowl shape
  • Improvement in performance (e.g. chip tuning)



Piston ring damage

Material washout in the ring area

  • Incorrectly installed pistons
  • Fuel flooding
  • Severe axial wear of the ring groove and piston rings
  • Ring flutter




Radial wear due to fuel flooding

  • Fault during mixture formation
  • Combustion defaults
  • Insufficient compression pressure
  • Incorrect piston protrusion dimension




Axial wear due to ingress of dirt

  • Abrasive dirt particles due to inadequate filtration
  • Dirt particles that are not completely removed during
    reconditioning of the engine (chips, blasting agent)
  • Abraded particles caused when the engine is being run in





Piston skirt damage

Asymmetrical piston wear pattern

  • Bent/twisted connecting rod
  • Connecting rod eyes bored at an angle
  • Cylinder bore not straight
  • Individual cylinders not installed straight
  • Excessive connecting rod bearing clearance



45° seizure

  • Excessively narrow fit of the piston pin
  • Seizure in connecting rod eye (inadequate lubrication at initial start-up)
  • Incorrectly installed shrink-fit connecting rod





Dry running/Fuel damage

  • Over-rich engine running
  • Combustion defaults (misfiring)
  • Insufficient compression
  • Defective cold-start device
  • Oil dilution with fuel



Cylinder liner damage


  • Poor/inaccurate seating of the cylinder liner
  • Use of incorrect O-ring seals
  • Use of unsuitable coolant agent
  • Insufficient prepressure in the cooling system
  • Operating temperature too low/too high
  • Restricted coolant flow



Bright spots in the upper cylinder area

Carbon deposits on the piston top land due to:

  • Excessive ingress of oil into the combustion chamber due to defective components
  • Increased emissions of blow-by gases with oil entering the intake air system
  • Insufficient separation of oil vapour from the blow-by gases
  • Frequent idling or short-distance drives



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