Rod bearing failure. What now?

[cornerbalanced]

Looking at the debris in your filter and your accounts of the events, I would bet the rod is damaged before the crank is. The bearing spins because it has to much clearance. That additional clearance also allows the rod to move "up and down" more on the journal. This effective hammering causes the rod big end to go from round to oval. SO even if the crank journal is ok, the rod may not be round anymore and installing bearings might work for a short time but not necessarily a long time.

With that said I'd 100% pull it apart if it only costs you $900.

If you are going to keep the car forever and can afford it go with option Vehicle Discussion if the engine is knackered.

Really good to know.

Currently planning on purchasing a new long block (compression/leak-down testing first), and having pretty much every gasket replaced, etc. Debating on doing head-gasket, and hotter (280/272 or 288/280) cams. Cost of rockers is scaring me, however, I'd really like to take advantage of cheaper labor while the engine is out. I've seen some members replace cams without doing rockers, but with my luck...not sure if that's a dice roll I'm willing to take.

[Tbonem3]

Well, there you go no offense.

I'm one of the most uncautious owners (in our cicle at least), subcribing to the belief that the updated bearings (or what newer cars came with) can go 150k (esp if 1200 mile service was done, and good OCIs, easy warm up), but even I opted to do it before that mark, at 141k (in 2014). hindsight for you now, I know, but for the bearing discussion, in general.

[cornerbalanced]

How many miles on the bearings ? Have they been replaced in the past?

'06 car (LCI bearings/rod bolts) ... ~153k miles. I have an entry in 2014 on CarFax for a oil pan gasket--weird to do an oil pan gasket so early in the car's life without doing rod bearings, but otherwise unsure. They were very high on my priority list of things to address.

[George Hill]

Looking at the debris in your filter and your accounts of the events, I would bet the rod is damaged before the crank is. The bearing spins because it has to much clearance. That additional clearance also allows the rod to move "up and down" more on the journal. This effective hammering causes the rod big end to go from round to oval. SO even if the crank journal is ok, the rod may not be round anymore and installing bearings might work for a short time but not necessarily a long time.

With that said I'd 100% pull it apart if it only costs you $900.

If you are going to keep the car forever and can afford it go with option 3 if the engine is knackered.

[c watson]

How many miles on the bearings ? Have they been replaced in the past?

[bigjae46]

If you score the crank at all and then have it ground down for oversized bearings or welded and turned...make sure the crank is heat treated again.

[digger]

pull the pan and have a looksy to confirm it is scored . nothing to lose but a few hrs of your time.

[Syfon]

OP I went through the same thing with mine a few years back. Heard it knocking at a set of lights close to home, shut it off & towed home. Upon removal of the oil filter, plenty of copper flake present. Rod bearing 3 spun and scored the crank.

I ended up pulling the motor and going through a full rebuild. Crank rod & main journals were machined 0.25mm with 0.25mm oversize acl race rod & main bearings.

If you hear the motor knocking and see copper in the oil, the crank will be scored; you can't just replace the bearings and call it a day. Doesn't work.

My crank was scored a decent amount (fingernail would catch), however it was able to be salvaged.

Imho, a new crank isn't necessary unless it's reallllly badly scored.

I'd rebuild your current motor and throw a heap of performance goodies at it. Fyi I reused my stock pistons/rods (replaced the rod/cap which spun and had all 6 balanced). Didn't see a point in going forged/ltw rods/pistons at standard compression as there is zero performance gain to be had.

If you go down this path, make sure you replace every gasket/seal/rubber on the motor, and ofc use new rings. Also ensure you run the motor in correctly to mitigate/avoid glazing the bores and loosing compression/burning oil/etc..

[cornerbalanced]

Haha...I guess I'm showing my age! I scored a 120k mile S54 (incl intake/exhaust manifolds and flywheel/clutch) for $2500 in 2016. Used to be able to find sub-100k mile motors for $3k to $3.5k all day long!

Wow…take me back! To be fair, our cars were also worth far less.

[bigjae46]

Luckily I’ve been finding S54s locally for “reasonable” prices ($4-5k) … so I’ll likely be taking that route. Like you said, the engine in my car will still be worth (something) parted out.

Haha...I guess I'm showing my age! I scored a 120k mile S54 (incl intake/exhaust manifolds and flywheel/clutch) for $2500 in 2016. Used to be able to find sub-100k mile motors for $3k to $3.5k all day long!

[cornerbalanced]

Option 2 is the best balance between cost and reliability.

But option 3...A new BMW crank isn't THAT bad...looks better considering the prices of S54s have gone up considerably. You can probably replace the crank and the offending rod. Then clean up the engine really well and pray the oil pump is good to go. There is risk here.

But...option 2 is still the best option. And you can part out the old engine and make a good chunk of your money back. Lang was buying damaged cranks...not sure if they still are. I bought a lot of 3 damaged S54s, sold the bad cranks to Lang and made about half of my money back. VAC buys blocks and heads but...they are a**holes and will lowball you. They tried to give me $100 for a good head when they sell a simple refurb head for $1200...I can get the same head cleaned, pressure tested, and new stem seals for half that and not have any of the typical VAC issues.

Luckily I’ve been finding S54s locally for “reasonable” prices ($4-5k) … so I’ll likely be taking that route. Like you said, the engine in my car will still be worth (something) parted out.

[cornerbalanced]

To be honest, when you spin a bearing in 99% cases the crank will be toast, so if that is the only thing you want to confirm, just assume it is bad.

That was my thought process. Waste of money to pull the pan, instead of going straight to pulling the engine itself.

I’ll likely just be purchasing a replacement motor, doing as much preventative stuff as possible to said replacement motor, and give my blown core to my mechanic in exchange for labor.

Will also be sending some trim to you in the meantime to have refinished while the car is down

[TexaZ3]

I’ll likely do this. Just not confident my crank will be in great shape after hearing the engine knock.

To be honest, when you spin a bearing in 99% cases the crank will be toast, so if that is the only thing you want to confirm, just assume it is bad.

[Mayan-Viking]

For whatever it's worth, this same issue happened to a friend of mine. He did a few consecutive hard launches with SMG when he spun his number 1 bearing. He took the crank out and saw some visible damage/scoring. He sanded it down the best he could, installed all new bearings and buttoned the engine back up. When he started the motor he heard a slight knock. He turned the car off and decided to sell it as a parts car for $6000. The guy who purchased the car took it home and heard nothing upon startup. He's still driving the car problem free after two years.

I mention that to give you some hope. I'd go ahead and try to fix it if I were you. But as others have said, until you see the crank with your own eyes you won't be able to make a proper decision.

Good luck!

[bigjae46]

Option 2 is the best balance between cost and reliability.

But option 3...A new BMW crank isn't THAT bad...looks better considering the prices of S54s have gone up considerably. You can probably replace the crank and the offending rod. Then clean up the engine really well and pray the oil pump is good to go. There is risk here.

But...option 2 is still the best option. And you can part out the old engine and make a good chunk of your money back. Lang was buying damaged cranks...not sure if they still are. I bought a lot of 3 damaged S54s, sold the bad cranks to Lang and made about half of my money back. VAC buys blocks and heads but...they are a**holes and will lowball you. They tried to give me $100 for a good head when they sell a simple refurb head for $1200...I can get the same head cleaned, pressure tested, and new stem seals for half that and not have any of the typical VAC issues.