n57 bad rattle, rod bearings?
Discussion
Sorry to see such a mess, how annoying.
This is the problem with sputter bearings, they are harder than the crank and destroy it when they run out of lubrication. Plain bearings give you more of a chance to save the crank if you catch it early enough.
Personally I would look into used engine options. The N57 is known to be not very cost effective to repair back to factory standards.
Have a look on H2 Motors YouTube channel. They rebuild N57s all the time and they go into great detail about common N57 issues. They've mentioned the heat of spun bearings can warp the block, so even a brand new crank from BMW may not save the engine unfortunately......well....not in the long term at least.
Good luck with it and thanks for sharing the carnage pics!
This is the problem with sputter bearings, they are harder than the crank and destroy it when they run out of lubrication. Plain bearings give you more of a chance to save the crank if you catch it early enough.
Personally I would look into used engine options. The N57 is known to be not very cost effective to repair back to factory standards.
Have a look on H2 Motors YouTube channel. They rebuild N57s all the time and they go into great detail about common N57 issues. They've mentioned the heat of spun bearings can warp the block, so even a brand new crank from BMW may not save the engine unfortunately......well....not in the long term at least.
Good luck with it and thanks for sharing the carnage pics!
I've now taken the engine out and disassembled everything. Didn't find anything wrong otherwise. Pistons and cylinder bores look great, original cross hatch clearly visible.
I've measured the block main bearings for diameter and straightness.
- Diameter wise they are all the same and all within spec - 60.00mm 90° from the split, and 60.02mm around the split pane
- Straightness, in both axes less than 0.001" deviation which was the smallest feeler gauge I had.
Given this, I'm confident it hasn't damaged the main bearings or warped the block, or anything like that.
The only thing a bit weird I did see is that the soot pattern around the injectors appeared to look a bit different on cylinders 5 (the spun rod one) and 4 (where I swapped injector 5 with for testing purposes). Not really sure if this real or just my imagination though. But maybe injector 5 failed via some distorted spray pattern, and that somehow caused all of this?
Also, piston 5 appears to have hit the head. The QR code imprinted on top of the #5 piston is now also visible on the cylinder head, if you look closely. There seems to be no damage to the piston, wrist pin, or head however. So I assume this was a result of the spun bearing where the piston between exhaust and intake stroke made light contact.
I've decided to rebuild the engine as I can't see why it shouldn't work, and it seems less suspect than going for a used engine which I also don't know if it will last. I've thoroughly cleaned the block and all other parts. There are only very few places where remaining glitter could hide, like say in the turbo.
I'm going with OE parts for crankshaft and a few other things, Kolbenschmidt for main / conrod bearings, and Elring for most of the seals/gaskets. Most parts have arrived now and I'm about $3,500 in so far. I'm still debating whether to replace the injectors as well.
Will still take me a few weeks to get everything back together as I'm doing it evenings / weekends and with somewhat limited tools. Curious to see if it'll work out or end up being a massive mistake
I've measured the block main bearings for diameter and straightness.
- Diameter wise they are all the same and all within spec - 60.00mm 90° from the split, and 60.02mm around the split pane
- Straightness, in both axes less than 0.001" deviation which was the smallest feeler gauge I had.
Given this, I'm confident it hasn't damaged the main bearings or warped the block, or anything like that.
The only thing a bit weird I did see is that the soot pattern around the injectors appeared to look a bit different on cylinders 5 (the spun rod one) and 4 (where I swapped injector 5 with for testing purposes). Not really sure if this real or just my imagination though. But maybe injector 5 failed via some distorted spray pattern, and that somehow caused all of this?
Also, piston 5 appears to have hit the head. The QR code imprinted on top of the #5 piston is now also visible on the cylinder head, if you look closely. There seems to be no damage to the piston, wrist pin, or head however. So I assume this was a result of the spun bearing where the piston between exhaust and intake stroke made light contact.
I've decided to rebuild the engine as I can't see why it shouldn't work, and it seems less suspect than going for a used engine which I also don't know if it will last. I've thoroughly cleaned the block and all other parts. There are only very few places where remaining glitter could hide, like say in the turbo.
I'm going with OE parts for crankshaft and a few other things, Kolbenschmidt for main / conrod bearings, and Elring for most of the seals/gaskets. Most parts have arrived now and I'm about $3,500 in so far. I'm still debating whether to replace the injectors as well.
Will still take me a few weeks to get everything back together as I'm doing it evenings / weekends and with somewhat limited tools. Curious to see if it'll work out or end up being a massive mistake
A few more details on the damaged parts:
- the old crankshaft had runout of 0.0065" / 0.165mm. Couldn't find acceptable values for this engine but it must be on the high end or outside of tolerance.
- the #5 conrod big end diameter is 53.59mm (0.01mm below spec), along both axes and most angles i tried. So seems like it took some material from the spun bearing. Not sure if someone could have machined this out, but I decided to go for a used replacement
- the old crankshaft had runout of 0.0065" / 0.165mm. Couldn't find acceptable values for this engine but it must be on the high end or outside of tolerance.
- the #5 conrod big end diameter is 53.59mm (0.01mm below spec), along both axes and most angles i tried. So seems like it took some material from the spun bearing. Not sure if someone could have machined this out, but I decided to go for a used replacement
Good stuff. Thanks for the update, I'm looking forward to following along.
Our engine is nearly out. I was stopped by the rain, and I couldn't find a wiper-puller for getting the rear cowling off the car. Hopefully I'll carry on this weekend.
It's looking very sorry for itself :-)
Our engine is nearly out. I was stopped by the rain, and I couldn't find a wiper-puller for getting the rear cowling off the car. Hopefully I'll carry on this weekend.
It's looking very sorry for itself :-)
Edited by carl0s on Wednesday 29th May 10:56
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