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| Damn JackintheBoxster - Wednesday, 4 September, 2013, at 10:18:39 am |
Found out today from my mechanic that my engine replacement from a year ago was due to a valve failure, not an IMS failure, so I don't know that I qualify for the settlement. Guess I'm just screwed, stuck with a replacement engine that I got a good price on and seems to be working really well.
Laz - Wednesday, 4 September, 2013, at 10:24:46 am |
| Re: Maybe the valve(s) failure relates to an out of spec - failing IMS bearing. JackintheBoxster - Wednesday, 4 September, 2013, at 10:26:49 am |
| How? It would have to be so out of spec that it was allowing timing to shift grant - Wednesday, 4 September, 2013, at 12:11:27 pm |
Laz - Wednesday, 4 September, 2013, at 12:17:49 pm |
Perhaps the engine analysis ended with seeing the bad valve(s,) without looking for a causam primam.
Edited 1 time(s). Last edit at 09/04/2013 12:22PM by Laz. (view changes)
Edited 1 time(s). Last edit at 09/04/2013 12:22PM by Laz. (view changes)
| Well, it is possible but it requires some sequence of events.... MarcW - Wednesday, 4 September, 2013, at 1:08:20 pm |
for this to work out...
Almost always by the time the IMSB gets bad enough for timing to shift and valve contact with the piston to occur the bearing is very obviously shot. LIke in balls in pieces shot.
However, as I've mentioned before I came upon a 996 engine with a failed IMSB and torn down. (I've posted pics of this engine before.) The tech told me the noise the engine was making prompted the driver to shut off the engine which saved the engine from destruction. The bearing race in the IMS was in horrible shape. I do not recall seeing the actual bearing but given the state of the race it had to be in the last seconds of its life.
The bearing had developed enough play that chain slack and resulting chain slap/whip had caused the plastic covering on one of the chain rails to start to come apart. Had the plastic failed completely or the violence of the chain compromised the ability of the tensioner to maintain suitable chain tension the chain slack could have resulted in jumped cam timing and valve/piston contact.
So, there is the possibility, if the engine failure postmortem was not thorough enough and the postmortem stopped as soon as the tech found the broken valve the assumption could have been the valve just failed on its own rather than failed due to contact with the piston arising from excessive play at a seriously failed bearing and the collateral damage to the chain tensioner which then let the valve timing get off.
But one can never know now.
Almost always by the time the IMSB gets bad enough for timing to shift and valve contact with the piston to occur the bearing is very obviously shot. LIke in balls in pieces shot.
However, as I've mentioned before I came upon a 996 engine with a failed IMSB and torn down. (I've posted pics of this engine before.) The tech told me the noise the engine was making prompted the driver to shut off the engine which saved the engine from destruction. The bearing race in the IMS was in horrible shape. I do not recall seeing the actual bearing but given the state of the race it had to be in the last seconds of its life.
The bearing had developed enough play that chain slack and resulting chain slap/whip had caused the plastic covering on one of the chain rails to start to come apart. Had the plastic failed completely or the violence of the chain compromised the ability of the tensioner to maintain suitable chain tension the chain slack could have resulted in jumped cam timing and valve/piston contact.
So, there is the possibility, if the engine failure postmortem was not thorough enough and the postmortem stopped as soon as the tech found the broken valve the assumption could have been the valve just failed on its own rather than failed due to contact with the piston arising from excessive play at a seriously failed bearing and the collateral damage to the chain tensioner which then let the valve timing get off.
But one can never know now.
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