what causes a engine to spin a brg

I am tearing down a ford engine off of a ford 5000 tractor and it has spun about three of the bearings on the main and rod and then the rod came apart and went through the block,what causes this? low oil pressure no oil pressure or low on oil,I wasnt driving the tractor so I am not sure but what I was told that the engine had been rebuilt not long before this happened and the engine looks clean and the gaskets look like they are not very old. Thanks
 
In addition to those: Contamination remaining in the oil galleries. Coolant in the oil. Failure to put a plug back in the galleries. Fuel contamination of oil. Wrong oil filter. Stuck relief valve in pressurization side of lube system. twisted off pump drive. Sheared pump drive. Correct bearings installed incorrectly. Improper torquing of bearings. A bad day at the bearing factory. The list just goes on and on. Jim
 
"I was told that the engine had been rebuilt not long before this happened and the engine looks clean and the gaskets look like they are not very old"
We know something was neglected during rebuild,otherwise the engine would have been good for a long while. Most likely the crank wasn't miced,turned or polished. Used tractor dealers,aka tractor jockeys are notorious for buying a smoking tractor at auction,roughing up cylinder walls,throwing a set of cheap rings in it then selling it as newly rebuilt.
 
I've seen more than my fair share of engines destroyed by silicone gasket maker. Some people love to use it on gaskets, when it has no need for it. They'll use way too much, especially on valve covers, lifter covers, or oil pans. When they tighten up the bolts, it squishes out, not only on the outside, but on the inside as well. After a little while, that stuff on the inside will start to peel off and make it's way to the oil suction screen, eventually plugging it up. No oil, and soon you have spun bearings and all sorts of fun stuff. Not saying that's your problem, but I know I've seen it a few times. Poor previous assembly doesn't help either.
 
Wrong bearings,no oil PSI,rods installed backwards,no oil. There are lots of things to cause the trouble,Check the bearings for the correct size.
 
(quoted from post at 17:49:03 11/18/17) I've seen more than my fair share of engines destroyed by silicone gasket maker. Some people love to use it on gaskets, when it has no need for it. They'll use way too much, especially on valve covers, lifter covers, or oil pans. When they tighten up the bolts, it squishes out, not only on the outside, but on the inside as well. After a little while, that stuff on the inside will start to peel off and make it's way to the oil suction screen, eventually plugging it up. No oil, and soon you have spun bearings and all sorts of fun stuff. Not saying that's your problem, but I know I've seen it a few times. Poor previous assembly doesn't help either.

I agree Boots, I've even flushed it out of crankshafts.
 
I wouldn't spend much time trying to autopsy that one!

In that bad of condition, best start over with a donor motor that is rebuildable.
 
(quoted from post at 16:49:03 11/18/17) I've seen more than my fair share of engines destroyed by silicone gasket maker. Some people love to use it on gaskets, when it has no need for it. They'll use way too much, especially on valve covers, lifter covers, or oil pans. When they tighten up the bolts, it squishes out, not only on the outside, but on the inside as well. After a little while, that stuff on the inside will start to peel off and make it's way to the oil suction screen, eventually plugging it up. No oil, and soon you have spun bearings and all sorts of fun stuff. Not saying that's your problem, but I know I've seen it a few times. Poor previous assembly doesn't help either.

A couple of years ago a tractor of mine didn't show pressure on the oil pressure gauge. I shut it down right away. After much head scratching I unscrewed the oil pressure gauge line from the block and found a piece of silicone stuck in the fitting. I'll have to admit I've been the only person to lay a wrench on that tractor engine since it was new. I use no silicone on gaskets now and if I use a sealer it's very sparingly.
 

If you really want to know you will need to lower the oil pan down, notice I don't say drop, and look at the bearings. Just match up the type of wear with the pics in your shop manual and it will tell you.
 
Those engines are known for bore cavitation allowing antifreeze in the oil,which is very good at wiping out crankshaft bearings. We have those engines sleeved for that reason if we overhaul them,and will not rebuild if the owner does not want to pay for the sleeve job.
 
What causes a bearing to spin in a Ford 5000, most likely anti freeze in the oil due to cylinder bore cavitation.
 
I agree.

I once rebuilt a Buick engine where the coolant passages between the cylinder heads and the intake manifold were plugged with silicone. Another time I had an oil leak on a valve cover on a Chevy 6.2 diesel. There was no gasket, just slopped full of silicone.

Silicone has its place, but nothing will replace an OEM gasket.
 

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