jumpToMain
siteLogo

Seizure in the piston pin bosses (shrink-fit connecting rod)

DESCRIPTION OF THE DAMAGE

  • Piston has only run for a short length of time.
  • No wear marks on the piston skirt.
  • The piston pin bosses have seized on the upper side, i.e. the side under pressure load (Fig. 1).
  • The surface at the seizures is clean bare metal; no traces of burned-in oil.
Seizure in the piston pin bosses (shrink-fit connecting rod) | Kolbenschmidt | Motorservice
Fig. 1

DAMAGE ASSESSMENT

The piston has barely any wear marks and can therefore only have been run for a short time. The piston pin already seized during the first revolutions of the engine.

The clean bare metal seizures are a clear indication of a lack of oil in the piston pin bed.

POSSIBLE CAUSES FOR THE DAMAGE

  • Piston pin bed was not lubricated before the piston was installed.
  • When shrink-fitting the piston pin into the connecting rod, the freedom of movement of the piston pin bed was checked immediately after inserting the piston pin by tilting the piston back and forth. The bed can suffer at this point as a result of the unusual temperature differences between the components that do not occur in normal operation.
Side info
Back