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  #61  
Old 02-11-2016, 09:20 AM
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I'm afraid these tests wouldn't reveal an imminent failure in a rod bearing. If the mains were significantly worn you might get an early indication with lower oil pressure (assuming you knew what it was accurately before), but no way of checking a rod bearing except for looking at it, in my experience. By the time it's knocking it's well down the path to trouble. And if we're talking about concerns over whether or not a bearing is about to spin, I don't know any way of assessing this before the event. I guess you might get a clue from inspection of the bearing fit surface and the locating tang, if things are getting really bad... but they tend to just go suddenly. And in an engine like this, if I have removed the bearings for inspection, there's no way I'm putting the old ones back.

Roger
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  #62  
Old 02-11-2016, 09:58 AM
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I'm afraid these tests wouldn't reveal an imminent failure in a rod bearing. If the mains were significantly worn you might get an early indication with lower oil pressure (assuming you knew what it was accurately before), but no way of checking a rod bearing except for looking at it, in my experience. By the time it's knocking it's well down the path to trouble. And if we're talking about concerns over whether or not a bearing is about to spin, I don't know any way of assessing this before the event. I guess you might get a clue from inspection of the bearing fit surface and the locating tang, if things are getting really bad... but they tend to just go suddenly. And in an engine like this, if I have removed the bearings for inspection, there's no way I'm putting the old ones back.

Roger
My understanding is that engine bearings depend on a film of oil to keep shaft and bearing surfaces separated. Bearings fail when the oil film breaks down or when the bearing is overloaded. The oil film is generated by shaft rotation. At rest, the shaft and bearing are in contact. On start up the shaft rubs the bearing briefly. Running, the shaft pulls oil from the clearance space into the wedge shape area between the shaft and bearing. The oil wedge lifts the shaft off its bearing and supports it during engine operations. With normal operating conditions and a continuous supply of clean oil the shaft and bearing surfaces will remain separated.
In other words, bearing failure is likely the effect of something else having gone wrong. Replacing the shells alone is largely pointless as either there is no problem or any problem will reoccur unless the cause of the wear is identified and rectified.
Logic suggests that if an engine has had regular oil changes and is treated with "mechanical sympathy" the bearings should last indefinitely. If the history and/or method of usage is unknown, a strip down and visual assessment might be appropriate.
Like many things I guess you make your choice and pays your money accordingly.
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  #63  
Old 02-11-2016, 10:19 AM
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My understanding is that engine bearings depend on a film of oil to keep shaft and bearing surfaces separated. Bearings fail when the oil film breaks down or when the bearing is overloaded. The oil film is generated by shaft rotation. At rest, the shaft and bearing are in contact. On start up the shaft rubs the bearing briefly. Running, the shaft pulls oil from the clearance space into the wedge shape area between the shaft and bearing. The oil wedge lifts the shaft off its bearing and supports it during engine operations. With normal operating conditions and a continuous supply of clean oil the shaft and bearing surfaces will remain separated.
In other words, bearing failure is likely the effect of something else having gone wrong. Replacing the shells alone is largely pointless as either there is no problem or any problem will reoccur unless the cause of the wear is identified and rectified.
Logic suggests that if an engine has had regular oil changes and is treated with "mechanical sympathy" the bearings should last indefinitely. If the history and/or method of usage is unknown, a strip down and visual assessment might be appropriate.
Like many things I guess you make your choice and pays your money accordingly.
I would agree with all that. However if there is a design problem or an error in the bearing spec/manufacture, as I believe was the case here (may well be wrong), that is good enough reason (for me) to do the 'recall'. BMW wouldn't have recalled all those M3s for no reason - it's an expensive process. But I agree, if the car's history is known to have been sympathetic it may not be a problem.
I'd have done it myself, but with two V8s in bits at the moment I have neither the space or time!
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  #64  
Old 02-11-2016, 10:41 AM
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Good point Roger, I wonder what engineering issue/risk caused BMW to instigate the recall? And did the recall include checks of other engineering tolerances/potential manufacturing defects as well as replacing bearings?

That information could crystallise the issue/risk for us.
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  #65  
Old 02-11-2016, 11:01 AM
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Just had a look for more detail on the E46 M3 engine recall (S54).
Technically, BMW issued a "service action." To quote BMWNA, "The problem has been identified as contamination of the engine lubricating system during assembly in combination with unfavorable tolerances in the engine oil pump for the M3 coupe/convertible produced from October 2001 through February 2002. These cars require replacement of the engine oil pump and as a precautionary measure, replacement of the connecting rod bearings. In addition, the engine control module will be programmed with the latest software, which includes improved cold start characteristics". This "service action" was done by VIN number and generally effected 2002 M3's manufactured between October of 2001 and February 2002.

So, if you need to spend money for peace of mind, its the oil pump that needs replacing as the priority, the bearings are only precautionary. Bearing failure is likely the effect, not the root cause! Also, would only apply to (if any) the very last of the S54 models.
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  #66  
Old 02-11-2016, 02:42 PM
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Interesting. One of my associates bought an M3 with the S54B32 motor in '08, which hadn't had the recall done. He took it in for service and the BMW dealer wouldn't change the oil pump, only the bearings. Bizarre.
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