Seizure in the piston pin bosses (with piston skirt seizure)
DESCRIPTION OF THE DAMAGE
- Piston skirt has seized on both sides, starting at thepiston head.
- Compression rings have become blocked in the ringgrooves.
- Seizure marks are present in the piston pin bosses.
DAMAGE ASSESSMENT
The focus of the seizures on the piston head indicates that this is where the damage originated as a result of abnormal combustion. Subsequently the piston rings seized up, and the seizure marks spread increasingly down onto the skirt area.
The combustion gases streamed past the seized compression rings and heated up the piston to such a point that the oil film in the piston pin bed became ineffective, and seizures developed here as well.
The combustion gases streamed past the seized compression rings and heated up the piston to such a point that the oil film in the piston pin bed became ineffective, and seizures developed here as well.
POSSIBLE CAUSES FOR THE DAMAGE
Abnormal combustion leads to a seizure due to the combined effects of insufficient clearance and lack of lubrication on the piston head and piston skirt and subsequently also causes seizures in the piston pin bed.