What are the causes of a spun bearing?
Engine spun bearing
- Thread starter bigsplash
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Pinging-detonation-oil starvation
Over reving, weak components, a machining error.
In certain cars, like older Volvo engines, it just wear and happens around 800,000 miles or so.
Originally Posted By: Pablo
In certain cars, like older Volvo engines, it just wear and happens around 800,000 miles or so.
In certain cars, like older Volvo engines, it just wear and happens around 800,000 miles or so.
Seriously though, could be any number of things, and most of them have been said. IMO though low oil, poor design and worn out parts are the usual reasons
reving the engine with no load on it.
Lots of silly advice in the above posts.
Oil starvation will cause a bearing to seize and maybe spin in only a few seconds.
If a bearing is old and worn, it may need thicker oil or it will make contact and fail.
Oil starvation will cause a bearing to seize and maybe spin in only a few seconds.
If a bearing is old and worn, it may need thicker oil or it will make contact and fail.
Originally Posted By: mechtech2
Lots of silly advice in the above posts.
Oil starvation will cause a bearing to seize and maybe spin in only a few seconds.
If a bearing is old and worn, it may need thicker oil or it will make contact and fail.
Oil starvation – mentioned above.
If a bearing is old and worn - mentioned above.
Nothing new in your post.
The only one I have doubts about is revving with no load......hmm....
Lots of silly advice in the above posts.
Oil starvation will cause a bearing to seize and maybe spin in only a few seconds.
If a bearing is old and worn, it may need thicker oil or it will make contact and fail.
Oil starvation – mentioned above.
If a bearing is old and worn - mentioned above.
Nothing new in your post.
The only one I have doubts about is revving with no load......hmm....
Revving the engine way up under load or not right after it's first started when the oil is still cold is another known cause of spun bearings.
"Lots of silly advice in the above posts." i have seen it. back in the dark ages i was working at a trencher mfg. they took a machine and jacked it up, then ran the engine at full rpm for 8 hours straight, in 3 days the engine would not turn over, a Wisconsin v 4. the bearings was spun, DA. just cause you havent heard of it doesnt mean it isnt so
Originally Posted By: morris
"Lots of silly advice in the above posts." i have seen it. back in the dark ages i was working at a trencher mfg. they took a machine and jacked it up, then ran the engine at full rpm for 8 hours straight, in 3 days the engine would not turn over, a Wisconsin v 4. the bearings was spun, DA. just cause you havent heard of it doesnt mean it isnt so
Finally, vindication for all of us that rev our engines at full RPM for 8 hours a day, for 3 days!
A question, why would they want to do that?
"Lots of silly advice in the above posts." i have seen it. back in the dark ages i was working at a trencher mfg. they took a machine and jacked it up, then ran the engine at full rpm for 8 hours straight, in 3 days the engine would not turn over, a Wisconsin v 4. the bearings was spun, DA. just cause you havent heard of it doesnt mean it isnt so
Finally, vindication for all of us that rev our engines at full RPM for 8 hours a day, for 3 days!
A question, why would they want to do that?
Originally Posted By: morris
"Lots of silly advice in the above posts." i have seen it. back in the dark ages i was working at a trencher mfg. they took a machine and jacked it up, then ran the engine at full rpm for 8 hours straight, in 3 days the engine would not turn over, a Wisconsin v 4. the bearings was spun, DA. just cause you havent heard of it doesnt mean it isnt so
I would think that unless they ran it out of oil, or there was a fault in the machine work (crank/rods/mains), that it should have taken the abuse. Those old Wisconsin engines didn't turn a whole lot of RPM.
Now, if the oil was old and broken down or they messed with the governor to purposely over speed it, then yeah, it would be bound to fail.
"Lots of silly advice in the above posts." i have seen it. back in the dark ages i was working at a trencher mfg. they took a machine and jacked it up, then ran the engine at full rpm for 8 hours straight, in 3 days the engine would not turn over, a Wisconsin v 4. the bearings was spun, DA. just cause you havent heard of it doesnt mean it isnt so
I would think that unless they ran it out of oil, or there was a fault in the machine work (crank/rods/mains), that it should have taken the abuse. Those old Wisconsin engines didn't turn a whole lot of RPM.
Now, if the oil was old and broken down or they messed with the governor to purposely over speed it, then yeah, it would be bound to fail.
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Originally Posted By: morris
"Lots of silly advice in the above posts." i have seen it. back in the dark ages i was working at a trencher mfg. they took a machine and jacked it up, then ran the engine at full rpm for 8 hours straight, in 3 days the engine would not turn over, a Wisconsin v 4. the bearings was spun, DA. just cause you havent heard of it doesnt mean it isnt so
Was the motor under load? jc
"Lots of silly advice in the above posts." i have seen it. back in the dark ages i was working at a trencher mfg. they took a machine and jacked it up, then ran the engine at full rpm for 8 hours straight, in 3 days the engine would not turn over, a Wisconsin v 4. the bearings was spun, DA. just cause you havent heard of it doesnt mean it isnt so
Was the motor under load? jc
I have been told that if a man who rebuilds an engine make some of the following mistakes, there will be a spun bearing:
1. Applying assembly lube on the backside of the bearing which does not face the crankshaft.
2. Sets clearances between crank and bearing incorrectly. Know if the bearing bores were rebored, due to the core having a spun bearing. Know if the replacement crankshaft was machined down to correct for damage or not.
3. The oiling hole in the bearing is not lined up with the oiling hole in the engine. Upper and lower bearings may be different, one with such a hole and one without. A bearing with no oiling hole placed above an oiling hole means that the crankshaft gets no oil, and that bearing gets spun.
1. Applying assembly lube on the backside of the bearing which does not face the crankshaft.
2. Sets clearances between crank and bearing incorrectly. Know if the bearing bores were rebored, due to the core having a spun bearing. Know if the replacement crankshaft was machined down to correct for damage or not.
3. The oiling hole in the bearing is not lined up with the oiling hole in the engine. Upper and lower bearings may be different, one with such a hole and one without. A bearing with no oiling hole placed above an oiling hole means that the crankshaft gets no oil, and that bearing gets spun.
Originally Posted By: Pablo
The only one I have doubts about is revving with no load......hmm....
Any revving incident that stretches the rod cap bolts is a likely cause of a spun bearing, IMO THE most common cause. The bolts stretch, the cap "walks" and the bearing locating tangs take a beating, then it spins in its bore. Very quickly (almost instantly) the oil supply cuts off because the rotated bearing shell blocks the oil feed hole... so a failure initiated by bolt stretch may LOOK like oil starvation on teardown... but signs of bolt stretch and cap walk will be there if you look for them. Oil starvation leading to galling can also be the initial cause by making the bearing adhere to the journal and then it will shear off its locating tangs and spin, but you'll usually see signs of starvation on multiple bearings rather than just one. The least likely thing I've seen here (my opinion) is an "old and worn" bearing causing it to spin. Yeah, if you open up .030" clearance maybe, butstill not likely as long as its getting oil.
The only one I have doubts about is revving with no load......hmm....
Any revving incident that stretches the rod cap bolts is a likely cause of a spun bearing, IMO THE most common cause. The bolts stretch, the cap "walks" and the bearing locating tangs take a beating, then it spins in its bore. Very quickly (almost instantly) the oil supply cuts off because the rotated bearing shell blocks the oil feed hole... so a failure initiated by bolt stretch may LOOK like oil starvation on teardown... but signs of bolt stretch and cap walk will be there if you look for them. Oil starvation leading to galling can also be the initial cause by making the bearing adhere to the journal and then it will shear off its locating tangs and spin, but you'll usually see signs of starvation on multiple bearings rather than just one. The least likely thing I've seen here (my opinion) is an "old and worn" bearing causing it to spin. Yeah, if you open up .030" clearance maybe, butstill not likely as long as its getting oil.
Originally Posted By: OceanDoctor
Originally Posted By: morris
"Lots of silly advice in the above posts." i have seen it. back in the dark ages i was working at a trencher mfg. they took a machine and jacked it up, then ran the engine at full rpm for 8 hours straight, in 3 days the engine would not turn over, a Wisconsin v 4. the bearings was spun, DA. just cause you havent heard of it doesnt mean it isnt so
Finally, vindication for all of us that rev our engines at full RPM for 8 hours a day, for 3 days!
A question, why would they want to do that?
High speed endurance tests are very common at all engine manufacturers, and they go for much longer than 24 hours. There is not a passenger car engine in production today that can't run for 300 hours at max power. This is an industry standard type of qualification test.
Originally Posted By: morris
"Lots of silly advice in the above posts." i have seen it. back in the dark ages i was working at a trencher mfg. they took a machine and jacked it up, then ran the engine at full rpm for 8 hours straight, in 3 days the engine would not turn over, a Wisconsin v 4. the bearings was spun, DA. just cause you havent heard of it doesnt mean it isnt so
Finally, vindication for all of us that rev our engines at full RPM for 8 hours a day, for 3 days!
A question, why would they want to do that?
High speed endurance tests are very common at all engine manufacturers, and they go for much longer than 24 hours. There is not a passenger car engine in production today that can't run for 300 hours at max power. This is an industry standard type of qualification test.
Originally Posted By: morris
just cause you havent heard of it doesnt mean it isnt so
And just because a random person gives a questionable anecdote, doesn't mean it is so.
This isn't a personal attack, but I think that story is not really enough to say "revving an engine without a load will spin the bearings."
just cause you havent heard of it doesnt mean it isnt so
And just because a random person gives a questionable anecdote, doesn't mean it is so.
This isn't a personal attack, but I think that story is not really enough to say "revving an engine without a load will spin the bearings."
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Originally Posted By: stephen9666
Originally Posted By: morris
just cause you havent heard of it doesnt mean it isnt so
And just because a random person gives a questionable anecdote, doesn't mean it is so.
This isn't a personal attack, but I think that story is not really enough to say "revving an engine without a load will spin the bearings."
We tried one of these test starting in the 80's with a 1964 Mopar 170" Slant Six.... That reminds me its time to fill up the fuel tank.... Would hate to have to start over after this long!
Originally Posted By: morris
just cause you havent heard of it doesnt mean it isnt so
And just because a random person gives a questionable anecdote, doesn't mean it is so.
This isn't a personal attack, but I think that story is not really enough to say "revving an engine without a load will spin the bearings."
We tried one of these test starting in the 80's with a 1964 Mopar 170" Slant Six.... That reminds me its time to fill up the fuel tank.... Would hate to have to start over after this long!
I have a video of a turbo Supra spinning a bearing at 210mph, sounded like a diesel until it finally gave up.
I guess that bearing spun because it was pushing a ton of boost and heat at a million RPM to get the car moving that fast.
I guess that bearing spun because it was pushing a ton of boost and heat at a million RPM to get the car moving that fast.
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