Robert, the problem is the bearings. Crankshafts and rod ends are subjected to large lateral pulses from the combustion pushing the pistons while also spinning at high revolutions. What saves them from self destructing is that oil is pumped through channels internal to the bearings and forced between the surfaces such that the crank and rod surfaces are riding over the bearing sleeves on a pressurized fluid barrier.
Eliminate the oil being pumped under pressure between the surfaces and the bearings quickly fail. When that happens, one bearing and its corresponding surface will typically seize and stop dead. If the engine is spinning at 2,000 rpm, there’s rotational inertia and inertia of the pistons and rods flying up and down. In the case of the bottom of the rods, they’re also flying side to side, in a “planetary” pattern. All that mass flying around pushing here and there will cause a rod to break if a bearing suddenly seizes.
^ Yes. Understood.
But do the bearing assemblies attaching the piston rods to the crankshaft not also dip into the oil pool and splash oil around?
I don’t understand why too full, (within reason), would cause harm.
Thank you.
Rod assemblies are not to splash in the oil in the crankcase because of the excessive and irregular drag that would create on the rotating assemblies and because all that splashing could cause the oil to become aerated, which would lead to low oil pressure and engine damage.
Now maybe 75 years ago it was different, some engines had “dippers” on the crank that were used to splash oil around the bottom of the pistons. But things have changed…
@Robert, read keith’s explanation (first post). “Too full” of oil did not cause the problem. The “too full” condition was likely because coolant got into the oil pan, was sucked up by the oil pump, and probably caused bearing failure.
By the way, the “dipping” of rod ends does happen in some small engines that don’t have oil pumps and therefore rely on splash lubrication.
The car has low miles for the age and if the car is clean with no rust, etc then I would give some serious thought to installing another engine. With a little footwork it might be possible to find a low miles engine on the cheap.
My oldest son lives in Utah and he was telling me on the phone last month his best buddy up there (who is into Volvos big time) found a 2000 or 2001 Volvo something or other up in Oregon for 1500 dollars; the complete car. He bought it and drove it back to Utah where he’s going to pull the motor and transmission to go in a project car.
It’s also possible that the overfill on the engine oil could be due to a cracked engine block water jacket seeing as how a connecting rod was thrown.
If it were me, I’d still want to know why the engine lost oil pressure seeing as how an oil change had been performed. Catastrophic engine failure so soon afterwards kind of raises the curiosity level a bit.
I think it’s all going to be heresy until you can tear the old engine down and figure out what caused it to fail–obviously oil starvation, but why? If you can determine the cause it may mean the place that changed your oil is liable and you can get recompensed, or at least it will give you some peace of mind knowing it was a coincidence.
Robert, Ase is, as always, spot-on, he definitely knows his stuff, however I would add that even if the crank were totally submerged, and the problems he referenced didn’t happen, it would still not provide the same protection as pumping oil into the bearings as I described.