Any main bearing experts...
Discussion
You can see a good main bearing on the left, this is the first one, then 5 and 6 show some wear. Now I cant see any marks on the crank so to speak. Could I just put some new shells in or will the same happen to them?
They look worn, not really scratched up.
Thoughts/opinions?
I was getting good oil pressure at 1500rpm(20psi) 0 psi at idle....
3.0 bmw m3 e36 engine ;(
They look worn, not really scratched up.
Thoughts/opinions?
I was getting good oil pressure at 1500rpm(20psi) 0 psi at idle....
3.0 bmw m3 e36 engine ;(
Have you measured the clearances?? If not, your guess is as good as mine as to if some new bearing would fix it for any length of time. (the general lack of embedded debris suggests "clean" oil,but the heavy scoring and even some "overpressure" pitting (esp of rhs bearing in pic) suggest some sort of failure of the dynamic lubrication film thickness)
cptsideways said:
My guess is you had no idea it was like this till you pulled it apart?
TBH it looks ok to me, a little difficult to tell as the pics are'nt close up.
What are they from?
No I did have an idea that they'd look like this, thats why I pulled it apart. I lost oil pressure at idle, from 18psi to 1.5psi, still fine and increasing with revs though upto 65ish PSI.TBH it looks ok to me, a little difficult to tell as the pics are'nt close up.
What are they from?
They're from a 3.0 e36 m3 with 160k on the clock. The engine now sits in my kitcar.
Zero oil pressure at idle?? Time to strip the engine right down and measure/recondition everything. Chances are it's also partly big end wear that has reduced oil pressure in some of the mains but not others depending on which big ends are fed by which mains. The shagged ones are however clearly well gone and no you can't just fit new shells and hope it'll be ok. It won't.
New oil pump, clean strainer, new shells, crank regrind if necessary and then it'll be ok - well apart from the bores and top end which are unlikely to be mint if the bottom end is that bad.
New oil pump, clean strainer, new shells, crank regrind if necessary and then it'll be ok - well apart from the bores and top end which are unlikely to be mint if the bottom end is that bad.
To me it looks like some dirt in the oil. This has come from somewhere and is likely to be distributed around the engine.
Why 5 & 6 have gone? - and the others are OK (?) probably just one of those things.
To just put new shells in and hope for the best is a tad optimistic IMHO. As the crank is OK, the bearings have done their job. They are designed to be the weak link in the chain. However, bearings fail for a reason, what that reason is, needs investigating.
What are the big ends like?
Why 5 & 6 have gone? - and the others are OK (?) probably just one of those things.
To just put new shells in and hope for the best is a tad optimistic IMHO. As the crank is OK, the bearings have done their job. They are designed to be the weak link in the chain. However, bearings fail for a reason, what that reason is, needs investigating.
What are the big ends like?
Thats not a contaminated oil failure imo, as there art no signs of embedded artifacts in the white metal (the "soft" layers on the shell are designed to catch and hold debris to prevent it scoring the crankshaft surface)
I suspect that the rotating parts are just a little undersized after 160k, and that some of the bearing have been slightly starved of oil (not totally, or they would be burnt/blue!) but enough to prevent the hydodynamic "wedge" of oil film building up properly (which should prevent metal to metal contact) The pitting also looks suspiciously like a shell metal fatigue failure (think how many pressure reversals the big end bearings will have had in 160k !!)
I suspect that the rotating parts are just a little undersized after 160k, and that some of the bearing have been slightly starved of oil (not totally, or they would be burnt/blue!) but enough to prevent the hydodynamic "wedge" of oil film building up properly (which should prevent metal to metal contact) The pitting also looks suspiciously like a shell metal fatigue failure (think how many pressure reversals the big end bearings will have had in 160k !!)
Max_Torque said:
Thats not a contaminated oil failure imo, as there art no signs of embedded artifacts in the white metal (the "soft" layers on the shell are designed to catch and hold debris to prevent it scoring the crankshaft surface)
I suspect that the rotating parts are just a little undersized after 160k, and that some of the bearing have been slightly starved of oil (not totally, or they would be burnt/blue!) but enough to prevent the hydodynamic "wedge" of oil film building up properly (which should prevent metal to metal contact) The pitting also looks suspiciously like a shell metal fatigue failure (think how many pressure reversals the big end bearings will have had in 160k !!)
The pics are main bearings ?I suspect that the rotating parts are just a little undersized after 160k, and that some of the bearing have been slightly starved of oil (not totally, or they would be burnt/blue!) but enough to prevent the hydodynamic "wedge" of oil film building up properly (which should prevent metal to metal contact) The pitting also looks suspiciously like a shell metal fatigue failure (think how many pressure reversals the big end bearings will have had in 160k !!)
i would presume like most engines that 5 and 6 are fed last (furthest away from the pump) and something in its long life would have bee drawn into the galleries. with no oil pressure the only thing to do would be a strip and full clean then plasti-guage to check the clearances. could also possibly be needing a line honing
Big ends worn furthest from the crank suggests run low on oil or run with significantly aerated oil.
If it was me (depending on what the value of the car is) I'd throw in a new set of big ends, an oil pump and filter and carry on. Does depend very much on how you value the car though.
Also, 20 psi @ 1500 revs/min is not good oil pressure (unless the oil is warm say 80°-90°C).
If it was me (depending on what the value of the car is) I'd throw in a new set of big ends, an oil pump and filter and carry on. Does depend very much on how you value the car though.
Also, 20 psi @ 1500 revs/min is not good oil pressure (unless the oil is warm say 80°-90°C).
stevieturbo said:
Max_Torque said:
Thats not a contaminated oil failure imo, as there art no signs of embedded artifacts in the white metal (the "soft" layers on the shell are designed to catch and hold debris to prevent it scoring the crankshaft surface)
I suspect that the rotating parts are just a little undersized after 160k, and that some of the bearing have been slightly starved of oil (not totally, or they would be burnt/blue!) but enough to prevent the hydodynamic "wedge" of oil film building up properly (which should prevent metal to metal contact) The pitting also looks suspiciously like a shell metal fatigue failure (think how many pressure reversals the big end bearings will have had in 160k !!)
The pics are main bearings ?I suspect that the rotating parts are just a little undersized after 160k, and that some of the bearing have been slightly starved of oil (not totally, or they would be burnt/blue!) but enough to prevent the hydodynamic "wedge" of oil film building up properly (which should prevent metal to metal contact) The pitting also looks suspiciously like a shell metal fatigue failure (think how many pressure reversals the big end bearings will have had in 160k !!)
;-)
ridds said:
Big ends worn furthest from the crank suggests run low on oil or run with significantly aerated oil.
If it was me (depending on what the value of the car is) I'd throw in a new set of big ends, an oil pump and filter and carry on. Does depend very much on how you value the car though.
Also, 20 psi @ 1500 revs/min is not good oil pressure (unless the oil is warm say 80°-90°C).
+1If it was me (depending on what the value of the car is) I'd throw in a new set of big ends, an oil pump and filter and carry on. Does depend very much on how you value the car though.
Also, 20 psi @ 1500 revs/min is not good oil pressure (unless the oil is warm say 80°-90°C).
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