Komatsu SAA12V140E-3 cylinder liner vertical cracks

Looking for help in identifying the root cause of vertical cylinder liner cracks. Any ideas on what has happened and what should be checked in the engine to find clues greatly appreciated. You can reach me by e-mail: elkin@uralremmash.ru cell: +7(919)911-19-11 ( UTC+4). Viktor.

An issue description:

  • After about 30 000 working hours the engine installed on a mining excavator Komatsu PC2000 was completely overhauled with new original parts.
  • After 1470 working hours after the repair engine was stopped due to coolant in the oil and white exhaust smoke on one side.
  • It was turned out that the cylinder got three vertical cracks (noon, 3pm, 6pm viewing from the top). Cracks go thru piston rings travel path starting 30mm below the top of the liner and finishing near the seat of cylinder o-rings.
  • A small piece of exhaust valve fell off (about 30%), but it made a minor damage to the piston and head but no visible damage to the cylinder liner.
  • There are no visible scratches on the liner, the surface looks good, the hone is fully visible
  • Piston also looks good. It has some minor polished areas near the vertical edges on the skirt
  • All piston rings are in good condition, not broken. But oil ring has stuck in the piston.
  • Cylinder head was slightly damaged by fallen valve piece. Mostly the valve seat was damaged. The injector stayed in working condition.
  • Connecting rod, piston pin, bearings etc - everything is in perfect condition
  • There was no abnormality identified in head bolts tightening.
  • Head gasket was in perfect condition - no signs of any blows thru the gasket
  • ECU memory contained just one minor overheat (105 deg C for less than 30 seconds) that happend after the failure was identified (while the excavator was moved to repair zone). No other errors were found in ECU.
  • In the memory of the excavator saved errors were found of low coolant level but the time when the errors occured was not saved.

Repair:

  • Cylinder head assembly, cylinder liner with o-rings, piston with piston rings, connecting rod bearings, head gasket, intake and exhaust gaskets - were changed for new ones
  • Everything was made according to manufacturer's repair manual
  • Engine then was tested and run into work.

Repeated failure:

  • After less than 200 working hours the issue repeated with the same symptoms but on the other side of the engine.
  • Coolant in the oil and white exhaust smoke
  • We decided to return the engine to our repair shop to find the root cause

After full disassembly we found that 2d liner is broken (after 200 hours after changing the first broken liner).

What we found:

1. Water filter (anti corrosion resistor) is full of dirt

2. After removing liners we found alluminium particles (drop shaped). Supposedly from bad water radiator repair procedure (welding)

3. Considerable amount of dirt that looks like soft sticky rubber

4. Broken cylinder valves that severely damaged cylinder head, piston, liner ets. We still think that broken valves was not the root cause since in the first case the exhaust valve was also broken (approx. 30% of valve plate fall off, the valve stem was ok) but there were no signs of damaging the liner (engine was stopped immedeately). Whereas this time engine was working approx. 8 more hours to move the excavator to dock.

Photos are below: