Engine Crankshaft Seal Failure causing bearing failure

[Yats]

The main bearings #1 and #2 of a G399 Cat engine failed after 17000 hrs. The inboard crankshaft seal was leaking for a long time prior to failure and heavily at the time of failure. The failed bearing closest to the seal showed the most damage and indicated metal to metal contact. The #2 bearing showed damage also but not as severe as the #1. There was no damage on the other bearings. We beleive the bearing failed due to seal failure. Documentation on causes of engine bearing failure state " The track of the pair of bearing shells nearest the seal exhibits symptoms of seizure, due to the oil film rupturing as a result of loss of oil pressure. " Can someone explain further how seal leakage in an engine causes bearing failure? We are being told that the crankshaft seals do not hold pressure and are only to prevent oil coming out of the block where the shaft pertrudes.

 

[smckennz]

Hi Yats
I have never seen a crankshaft seal designed to keep oil in the main bearing. Normally the bearing starts to fail which increases the clearance. As the shaft wobbles around inside the bearing, the seal is subjected to large deflections, and tears. Perhaps the failed seal let dusty air into the crankcase. But since the bearings are under oil pressure, this should take out all the bearings if the filter is defective.
Unfortunately, I have to agree with what you are being told and not what you believe. You have no doubt checked your oil pump and galleries.

Good Luck

Steve

 

[jet1749]

smckennz looks to be right on the money. The crank seak is there to keep the oil in and the c**p out. If the mains were worn the crank would deflect and either damage the oil seal, or the oil seal would be unable to effectively contact the shaft. Either way an oil leak is the result. It looks like you have got the cause and effect the wrong way round.