Very true. And so if I’m wrong, pray tell how a computer could deduce the issue? Maybe part of the process is an oil change to a known viscosity?Quote:
Originally Posted by BradC
Very true. And so if I’m wrong, pray tell how a computer could deduce the issue? Maybe part of the process is an oil change to a known viscosity?Quote:
Originally Posted by BradC
The first sign of failed big end bearings is the oil light coming on. As mentioned, when the clearance is exceeded even slightly, the oil leaks out past the bearings at a rate of knots and the oil pump can’t keep up, hence pressure drops.Quote:
Originally Posted by LRD414
If they know precisely the oil pressures to expect at each RPM, they could run analysis across the engine and spot an issue. This would then lead to secondary level physical investigation.
Are the failures on big end bearings (I.e. connecting rod to crank) or crank main bearings?
From the post I've seen, the issue appears to be the crank main bearings, I.e. those that hold the crankshaft in place in the block.
To be honest I’m not sure it matters given the end result is the same. You say potaaato I say potayto [emoji2]Quote:
Originally Posted by Eric SDV6SE
Either way the end result is a cactus.
I think it’s mains.
I've seen the same, but if I'm not mistaken the big end lubrication comes from the gallery openings in the main bearings, so once you've spun a main you'll starve the big ends. Haven't seen any images of a leg out of bed, but I'm pretty sure I saw a couple of images of bent rods. Can't find them now however.Quote:
Originally Posted by Eric SDV6SE
The failure mode to me is instantaneous due to bearing shells rotating to block the oil gallery. It’s not a wear and tear issues to my mind like a flogged out rattling bottom end.
But a bearing spins because it catches the rotating part. A bearing will not spin without a force pulling it. If you’ve ever installed a bearing into a shell, there is a decent force that keeps them in situ, exactly where you place them. They’re designed with a tension so they fit tight as. If a bearing turns and blocks a gallery, you can be sure the journal was not happy and the journal bound to the bearing to make it turn. The lead up to this was a problem - I find it far fetched a bearing moves itself then causes the blockage.Quote:
Originally Posted by PerthDisco
True, but if a bearing cap was loose that could happen pretty damn quick.Quote:
Originally Posted by DiscoJeffster
When you see in those car production tv shows they have machines that lift and fit things like the pre-assembled head and bottom end units whereby the entire unit with bolts goes on and is instantaneously and automatically torqued up.Quote:
Originally Posted by BradC
It does not rely on old mate remembering to do bolts up in 1-3-7-2......... sequence.
You would think a random check with a torque wrench would be made from time to time. So one of these machines randomly faulting would seed dodgy units amongst the good ones.
But this occurring continuously over 10 years and different engine types seems crazy.
I wonder if the spun bearings have been deprived of oil at high speed then overheated because pressure has been lost elsewhere, that is the spun bearing being a fatal consequence rather than the underlying cause. If so then regular monitoring of oil pressure might provide some early warning which if investigated early enough could prevent the catastrophic result.