Piston head seizure on a diesel piston
DESCRIPTION OF THE DAMAGE
- Localised seizures that mainly occur on the piston top land.
- Surface of the seizure areas is rough and worn, in some cases larger pieces of material have been torn out.
DAMAGE ASSESSMENT
Due to a fault on the injection nozzle, non-atomised fuel was able to reach the cylinder wall, where it weakened the oil film to the point where the piston was running dry without any lubrication at all. As a result, the piston top land seized so severely that it was temporarily welded to the cylinder wall. This caused chunks to be torn from the piston head.
POSSIBLE CAUSES FOR THE DAMAGE
- Injection nozzles that are leaking, dripping after injection, clogged or the wrong type.
- Blocked injector nozzle needle due to bent injection nozzle body (incorrect tightening torque).
- Incorrect injection timing (start of delivery).