- Piston Rings: Blow-by.
Leakage of Combustion gas past the piston rings (blow-by) is a natural Consequence of sticking, collapse or breakage in the later stages, when blow-by becomes persistent, it is usually due to advanced ring breakage, caused by Collapse.
Blow-by is indicated by black, dry areas on the rings and also by larger black dry zones on the upper part of the liner wall which, however, can only be seen when overhauling the piston (or when exchanging the exhaust valve.
- Deposits on Pistons
Usually some deposits will have accumulated on the side of the piston Crown (top land). Carbon deposits on the ring lands indicate lack of gas sealing at the respective rings.
If the deposits are abnormally thick, their Surfaces may be Smooth and shiny from rubbing against the cylinder wall. Such Contact may locally wipe away the oil film, resulting in micro-seizure and increased wear of liner and rings.
