Why Can BMW Rod Bearings Fail?! 

On my lunch break at BMW watching bmw vids. Life can’t get better than this

I've just been through exactly the same situation with King rod bearings. I did mine just as routine maintenance, as the car had previously been abused before I took it on. The old bearings were slightly scored and one of them was showing more wear compared to the others. We went with the CR222SV shells on a standard, unground crank (which checked out within spec when mic'd up). All clearances checked with plastigauge thereafter. After driving the car for no more than a few miles or so, there was a lot of knocking from multiple cylinders and when the car was taken apart again, every single shell was scored and two were down to copper. Thankfully, the crank was fine and undamaged. I decided to go with the more expensive, colour coded OEM shells from that point on and it's been fine ever since. Really, really not sure about King to be honest. Definitely left a bitter taste in my mouth.

I have learned every inch of my car from this channel alone. Thank you!

I’m so glad you made this video. Also I appreciate your transparency and pursuit of the truth, which is one reason why I watch your channel. That said, there has to be a reason for it, and when you find it it will be obvious in hindsight, keep after it!

Still think it was your oil pump. The score lines you noted on the impeller vanes would have been the cause of fluid cavitation. Again, pumping "foamy/frothy" oil. The comments I made in one of your previous vids regarding all the many Audi/VW oil pumps I've replaced, many of them I took apart and every one of them also did not "look" too bad with score marks/pitting or worn out. Again, the fluid cavitation. In heavy industry like mining where almost everything runs on hydraulic systems, replacing oil pumps is very common even with rigorous oil maintenance. In fact, when I went to diesel/heavy equipment tech training, checking the hydraulic oil for excess cavitation (foamy oil) was a frequent "check list item" to help spot failing oil pumps because that leads to failing valve block assemblies and cylinders, meaning repair bills that'll make BMW repair bills look like chump change. I can't help but note I'm quite surprised some BMW engineer decided to use a Vane type pump as opposed to a Gear/Rotor Gear type of pump. Gear pumps are more durable and more forgiving to contamination (metal debris). Vane pumps, not so much but cheaper to manufacture. In the automotive realm, just about all Power Steering pumps are Vane type pumps and also fail quite often (i.e. loud whining/whirring noise complaints). So I'd guess oil pumps need to be added the "maintenance" list when doing your N54 oil pan gasket. Maybe it's no surprise BMW markets/touts the B58/S58 engines having a vastly improved oiling system.....

This is better than a murder mystery. Hoping you might present information from an oil analysis. I would think that if the bearings were starved of oil you'd see bearing material in the oil. However, if it was general contamination, I'd expect to see other alloys, steel, etc in the analysis as well. Another thought is to check the small ends of the rods for bearing damage, which would indicate general loss of oil to the crank/rod. Agree with the points of using a higher precision measurement than Plasti-Gauge. Suggest using a micrometer on the crank and bearing journals in at least 2 opposing positions on each journal and a bore gauge on the connecting rod journals. perhaps there's a local machine shop that wants to do a collaboration like you did on the ECU MOSFETS.

Quite the mystery! Amazing engineering really with these crazy tolerances and machining. Very interesting, thanks!

I love your videos, I work as a nurse and love working on cars. Been building honda and mitsubishi engines for 30 years as a hobby. Just started working on BMW's for that last 4 years. Just got done rebuilding my 2nd N54. I've made my mistakes over the years and definitely learned from them. That's why I love videos such as yours. I was thinking about your spun bearing situation. Sometimes it's the simplest this that causes the biggest problems. I don't believe it was the clearances on the bearings or the pump itself. I believe it was the oil pickup tube or the pickup tube o-ring gasket fitting to lose and sucking air along with oil. Like trying to drink a soda from a broken straw. You will register enough oil pressure for the oil light not to trip but starve the engine at the same time. The reason I said this is because it has happened to me with one of my first rebuilds. All my rod bearings were toast. Just a thought. Great job on all your videos my friend. I've learned alot from you.

Do some research on rod side clearance to the crank webs. Not sure if the N54 is afflicted but other BMW engines were constructed with insufficient side clearance. This meant that the oil wasn't able to bleed-out from the bearings at a sufficient rate and got overheated / overloaded. The optimal bearing axial and side clearances vs journal size and rpm are easily looked up - proper tuners know them. Why BMW didn't stick to tried and tested tolerances is a mystery.

Had a bad rod bearing as well on my old 07 335i. Oil level sensor had a malfunction combined with a oil pan leak. Eventually the engine ran low on oil. Be careful guys. Especially on early cars with leaks. Ended up replacing the engine with a used one for $1,700. Not the end of the world but still not a fun day.

Maybe a micrometer to measure size of crank journal. Plus dial bore gauge to measure with bearings bolted into rods.

Just a comment on the rod strength of the N55, they share the same rods as the S55, so it isn't the rod flex that's causing them to spin. Otherwise it would be widespread on S55 tuned engines, which readily make over 600hp.

After watched your video and all the comments on kings bearing… I believe the best choice for all of us is don’t use kings bearing😂

You're floating layer of oil plays a big role in preventing metal on metal contact. Additional clearance in your bearings gives clearance for higher viscosity oils that can handle heavier loads.

Not sure about N54 but N55 uses a solenoid to vary oil pump output. This is the solenoid at 10-11 o’clock from the crankshaft when looking at the front of the engine. Purpose is for fuel economy/engine load but to ME that variable oil pump can cause oil starvation in the bearings towards the end of the block if there is any pressure drop throughout the system- chain tensioners, VANOS, rod bearing oil clearance, main bearing oil clearance, oil squirters, oil cooler, etc. Different engine, but the Hyundai 2.0 I4’s 2010-2013 were plagued with spinning bearings. To my knowledge there’s no definitive answer yet but what I noticed in the engine I tore down was that the bearing condition was worse as you moved from the pump. The oil pump creates flow and pressure is a function of the flow being restricted (where bearing clearance is critical). If clearance is too high in the other rods or mains, it can starve the other bearings and components further from the pump. You may consider checking clearance on all rods and mains in your search for why your engine failed.

with what happened prior with your chain sprocket and all that metal it had to slowly plug up one of your ports until it wasn’t getting proper oil supply. Then laying on the petal without you’re oil being the proper temp... boom! Love your video’s man say it every time.

Bearings can also fail from too thick oil. If the oil is not considered when using tighter bearings you will get too high pressure and not enough flow to critical parts of the engine.

It’s definitely combination of not up to temp and bearing crush in my opinion. I have the exact same bearings as you, but I don’t have stock rods. I’m using molnar rods with arp2000 bolts. I also have all rrrrrr markings on my crank.

OK, just a little late in here, but have now seen the original vid of your removed bearings after the oil pump chain failure. From my experience (I started building engines over 50 years ago) when you see "tram tracks" on your bearing shells, you have foreign matter in your oil system as the cause. This is not a wear issue. I have seen bearings with 200K on them and while the load bearing shell (upper) babbit surface is worn down to expose copper, they are smooth across the bearing face. In light of this, your engine should have been removed after the chain failure and all the oil galleries cleaned out and for me, I would have had the crank journals linished at a machine shop and measured as well to see if it needed grinding undersize. I expect having material in your oil galleries has been the cause of this second failure. I would also have removed the mains once I saw this damage on the big ends. A bit long winded, but here in Oz, Beemer parts are cripplingly expensive, so we cannot be too careful, especially on a customer car. Nice vid though.

I have 260k km on my N54 and the only things I have changed are the turbos for Td04s at 180 km's and suspension other than that just general maintenance , and it still puls like a train.

Hope you havent already answered this but the N55 has a known issue where the chain tensioner fails. So much so that theres a class action lawsuit currently going on regarding failed N55 engines due to the chain, the chain tensioner, and the oil pump. Do you think those characteristics were born in the N54 and carried over to the N55 or is it a completely different issue? Absolutely love the videos! Keep em rolling!

I'm going to start this off by saying I love watching your vids, and I don't even have an N54.... ('11 E90 335xi M-Sport 6MT) Yet I watch just about all of them. lol Plastigauge is a ballpark check. It surely will indicate if you did the math wrong (from mic numbers) or have a wrong size part, so it's not like it doesn't have value. It's just not going to be accurate enough to compare tolerances between OEM and Aftermarket bearings, IMO. When you use PG, it's critical that the joint is immobile. In your case, it looked like those rods were swinging free when you torqued them down. Normally the piston in it's bore would hold everything still while you're torqueing those rod caps. Maybe call around to a couple automotive machine shops and see if they won't be able to get you some more precise numbers?

My thoughts: first of all any debris that gets sucked up by the oil pump is directly put through the oil filter, (I have seen cheap, non OEM, filters split in half before on the tuned n54s I have worked on). but damage from debris will usually leave a sizable groove on the journal and or bearing surface, that being said I think it is safe to rule that out. The only way I could think this might be caused by debris is if the oil pick up some how got blocked and momentarily starving the motor of oil. The temperature mentioned is also concerning, 120 degree oil temp might not affect rod bearing clearance too much but more so piston to bore clearance and if you logged 28psi and the pistons were not fully expanded in bore that might have caused it to unevenly load the rod bearing at close to the max load they can handle. I DONT think you did anything wrong with the assemble of the bottom end. It is unfortunate to see an n54 die, all the reading I have done on building M5x and s5X motors all seem to have a similar theme, sealed, well maintained bmw motors that are tuned within their limits will out last any motor that has been tampered with no matter what parts or how carful/experienced you are with reassembly. best of luck with the new motor. keep up the great content :).

Any follow up videos to what happened to this engine or oil lab results ? I’m going to tackle the job of changing my rod bearing ( given the confidence by watching your videos & links to parts & tools ) took it to BMW said they used a camera & said something knocking on Cylinder 1 & 2. Gonna send my oil to get analyze & see what comes up. NEVER did internals but pretty meticulous about doing everything right. I already done a n54 swap, I got a second motor that I will practice & see if I build up but want my engine inside the car to get back running before I go crazy spend tons of money on something I never done before. Overall LOVE the content I’m a new viewer, would love if I can ever reach out to you with questions ofc I’ll PayPal or donate to your build for any help. Thanks bud keep up the great content

The ellipticity ratio of the aftermarket bearings may have been different.

Have you checked with the manufacturer of the bearings for their input?

120° F should have been sufficiently warm at anything less than 3/4 throttle. So you say the oil pump chain tensioner failed at idle yet you do not think it caused the spun bearing? You might also want to inspect your Vanos pump just to be certain no metal parts went through it. Thank you for taking the time and posting.

I'd change the oil cooler and flush out all the lines blow out all the passages. I would measure the con rod at several points on it's circumference for elongated and twisted also i wouldn't go for a bigger gap... maybe its time for aftermarket conrods and have them cryogenic treated then get the ARP bolts then get then check afterwards and do what ever machinist needs to do to get it true. And balance the con rods with the bearings and same with the pistons then all with the crank. It would be a good ideal to see if the the crank journal is flat maybe at one point on it 🤔...

Watched the whole video and really seems like the culprit are the bearings themselves.

currently in the process of building my N54 - i spun a rod bearing and then had a machine shop take off 0.25mm on all the journals. I'm putting in oversized 0.25mm king bearings that are calico coated. all of my clearances are pretty much the same as yours, roughly 0.038. still wondering what happened here, and hoping this doesnt happen to me haha

If you flushed your old oil cooler im curious if you would find debris.

in my opinion it could also have been due to the assembly oil. That looked very thick. Almost like fat. May have clogged the holes at the beginning.

Interesting videos man, have you considered having your oil lab tested for contaminants or clues? Had my n54 fail on cyl 6 bearing and lab results indicated high fuel content in the oil caused by leaking injectors. Never followed up if this was the cause of the failure so would be curious to see any similarities. On a new engine now and I get my oil tested every oil change.

1) There a perfect circle when inserted in to the rod, not out of the rod. 2) You're "egg shaping" the bearing torquing and loosening the rod without shimming the rod with a file gauge. 3)Check the oil pick up tube, it might be clogged, when the serpentine belt goes out, it sucks it in the engine, and people replace the front main seal and never take out the oil pan and check what's going on in the engine.

I don't know if you've ever seen any of papadakis racing videos here on RU-vid but he shows you how to build an engine and check for bearing clearances and it says plastic gauge is great for just generally checking it but it's not accurate, maybe you can borrow from your friends at that auto shop the tools to properly check the bearing clearances to get a better idea what the actual real clearances are between the stock and the King bearings

When checking rod bearing clearances with plastic-gauge use the old rod bolts and torque AND stretch the bolts or your reading will be off. You can only torque and stretch the rod bolts twice so plan on buying new ones. Also if you’re thinking about using the ARP rod bolts, don’t! If using ARP bolts you’ve gotta assemble the connecting rod, torque, stretch then line hone cause it’ll egg the connecting rod-ask me how I know.

I have an N55 that failed the no1 rod bearing TWICE within 20 km. Priming of the oil pump and oiling system is critical - airlocks in system I suspect. if not done bearings spin. My research reveals that if they do not spin immediately than enough damage is cause that they spin soon after. my experience anyway - third set of bearings going back in shortly with primed pump, primed system and oil pressure gauge to confirm oil pressure drops from potential airlocks. This included priming oil cooler if you have one fitted.

This is so heart breaking. and confusing. Did some debris despite all the flushing not get removed? Did any oil related valve or VANOS piece somehow cause a oil pressure drop? Have you inspected all the oil passages to see if something clogged and then bearing failed and then creating debris to etch the rest?

The. color codes sizes. rrrrrr are all standard, upper and lower, the the other colors would be ,5 and .25. Last year I done all new king rod bearings and and arp bolts. I done everything to a t, I done proper break in, around 1500 miles, I lost nu4 rod. I’m in the same boat and can’t find a good answer, and this motor is 60k on it. I couldn’t find any answers, but leaning towards detonation. I run 93 and around 18psi on 16t, but they all looked like yours. I’m thinking the king are much harder than oem ones, but can’t justify the price per shell. I’ll try it again and see how I make out

Me too, I notice a diebres last week on my freshly build engine after just 2000km , I ordered ACL ( same standard size) hopefully I still could save it 😪

incline/ hard acceleration causes oil starvation

Did the car go kablooey BEFORE or AFTER you started using that üro aluminum oil filter cap? With this new engine replacement, using the same metal cap, if it does this again, you will know 98% the reason. I know you have your doubts and you said you checked your oil pressure, but I just could not bring myself to install that metal cap because the center core cage just didn't fit correctly and the metal spring was resisting movement to the point where I could not move it with my index finger, whereas the stock center core spring could be easily moved with my index finger. I have no idea what that center spring is for and what it does, but the vast difference in resistance itself with the fact that the center cage would not click into place was enough to make me reject using the part.

I was watching your timing chain tensioner video from a while ago .. and it got me thinking.. maybe putting a new tensioner on high mileage car is not good idea , because you have all that tension now pressing against old chain , maybe that’s excelereted engine failure on your car in first place , maybe am totally wrong about this .. but kinda makes sense that tensioner and chain age together .. like I said just a theory.

Did you also use 5W-40 with the stock bearings or did you switch to 5W-40 when you changed to the king bearings?

So would it be smart to use 0.25 bearings for a high performance application with a std crankshaft

Now I’m scared, I ordered King bearings for my N55….seems like king bearings killed your engine….

I came across one possible reason which was mentioned in this video: rod bearing material softening due high oil temperature. First scoring a bit and losing the capability a bit to hold even film becoming more prone to metal to metal contact, getting more chewed up and eventually spinning the bearing. Source of heating thought: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-v4CRTPGP5M0.htmlsi=2HdTiAemDGZ8PddB

thanks for explaining the process! love your content

Can it be like you said ? The King bearings had more clearance and possibly decreased oil pressure to the journals causing the bearings to score ? Is it possible to have installed the bearings in the wrong orientation?

Is it possible that some of the bearings were the wrong size but still packaged with the correct ones ? There’s been many stories of KING packaging undersized / oversized bearings with standard sized ones on bmw forums … I’m going to do this job on my 07 335 and ordered the STD sized bearing from KING and one of the bearings were undersized and the rest STD. I had to reorder and check every individual one to be safe

2013 bmw x1 (n20) Rod bearings have failed yesterday. Loud n clear knock 😔

Smart guy, thanks for the information!

She didnt like getting tampered with 👍

Any new improvement for the e90 ? Wanting to see any other upgrade from you like coilovers

You mention when it failed. The temperature is 120F. Was it coolant or oil temperature? From the N55 In the warm up phase, the oil temp lags the coolant by 10C and (below 120F, oil pressure is ~100psi; over 120F it drops back to 40psi; will double check)

Maybe I'm missing something but it seems pretty clear to me what the variable here is, you had OEM bearings for 200k miles then you put aftermarket ones and they spun almost straight away - it's the aftermarket bearings. They're probably designed for racing and not to be used with the stock oil pump or to ever be revved at all until the engine is up to temperature. Which makes them a terrible idea for a road car.

Hey Buddy, i assume you are running King bearings on your car, is it still kicking ? im thinking of buying kings for mine, need some advice. Thanks

So changing. The bering with kings bering is no good ?

What oil brand/weight were you running? Could the oil you used to flush the engine cause it to ruin your bearings? I thought you used a non synthetic oil to flush it.

If you don't mind me asking, after the king bearing install ; did you do a semi break in period? I suspect tiny issues actually took place immediately after the new bearing install.

Also since you mentioned the clearances were a bit looser than stock bearings do you think you might have needed thicker oil maybe 5w50 to compensate for the extra clearances ?

n55 possibly did this. seized up and manual cranking wont work.

theory B it is...starvation from debris in the oil holes in the crank maybe

Bearings fail because of oil not at operating temp when redlining engine and hard throttle applications without properly bringing engine to temp -Bmw master tech

I didn’t know your rod bearing replacement failed. Shame there’s no reason for why it did. Do you think if you used bmw bearings it would have been ok?

Did you say your car was running for 10 minutes therefore the oil wasn't hot enough ? 10 minutes of driving should be enough time to bring the oil up to normal operating temperature , regardless , I know a few people who done every N54 preventative maintenance you can think of and still spun a bearing ,

It's important to note that all 2014+ N55 bearings share S55 bearings.

during the oil pan gasket change on my N55 E90 at 103K miles, I removed one of the rod bearing caps to examine the rod bearing. Since the bearings looked good, it buttoned it back with two new bolts and 20NM plus 140 degrees. After buttoned up, I tried to move the rod bearing laterally, and noticed the movement is much less than other five rod bearings. Wondering what caused it to be tighter?

The tendency for the connecting rod bearings to wear out earlier at BMW than at other premium manufacturers is something of a "tradition" and is also based on the fact that the crank pins as well as the main bearings are relatively small and narrow in diameter. This facilitates or benefits the engine's engine revving power, which is already legendary at BMW. However, one must also note that some contemporaries tend to be careless, if at all, with warming up. Internal combustion engines now have a work area in which they function optimally. The cold state of aggregation is not one of them!😉

hey can i please contact you somehow, im trying to retrofit my acc to my e90, but i need help please. cant find my way out rn, im so confused. the video u made for it didnt help me out

Have you tried contacting king bearings and asking them what could’ve gone wrong ?

I’ve got a f10 m5 it’s got a knocking noise I believe this happened after a 2nd gear pull but I’m not sure degeneracy did not drive it after I heard the noise. dropped the oil filter there is definitely a hint of some shavings, you think I might be able to get away with just replacing the bearings or is it too late?

Great video!

Is you're torque wrench calibrated? maybe since you did not change the main/thrust bearings ;may have caused clearance imbalance?;you have needed tighter bearings ;0.0001"? 🤷‍♂️; Get crank and rods measured and balanced to rule out damage.

I think I understand. No I don't!!!

Faulty oil level sensor ? Causing low oil levels

I have king bearings in my D16 Honda not because I wanted them but because that's all I could get in 2 weeks now I'm worried

N55s have this problem. It is a common issue.

can this happen on a 2015 BME x4 35i? N55?

I'm looking into getting 2008 m6 and the m6 have that problem. I was reading about the weight of the oil. The oil break down so I spoke to some engine builder and they say you need a thicker weight oil. What do u think

Are those cracks on the E90’s windshield?

I got a F10 N55 Engine #3 Rod bearing failure after I done the Rocker cover & Oil Pan Gasket replace, 1st pull the Engine Out, Go to Mechine shop polish the Crank shaft, and put New BMW Bearing (Main Bearing and Rod Bearing) 1start running smooth, after 1hour idle #3 Rod Bearing failure again. 2nd Pull the Engine,Clean all the Oil Line all over the Engine Make sure notting is clogged up,Then put new Bearing and New Oil Pump,Still the same. Now gonna 3nd time Pull the engine out... Can anyone Give me an idea? Thank you.

those stock 200k miles bearings look better than my e46 bearings at 90k miles

Did you ever find out why your bearings failed?

So why 7 b’s for 6 rod bearings I’m confused

Would it be possible for you to send me a photo of all your rod bearings in high detail?

Oh no. You should use BMW bearings now you don't know What cause The failure :\ I'm going to do my 540 but For sure I'm putting factory bolts and rod bearings.

What’s the mystery? You lost oil pressure and scored the bearings causing a failure. Something got trapped in your oil pump.

5w 40 wow

they fail because of poor engine design. Too many revs for such a long crank. These things were failing like mad when the e46 M3 first came out.

Could the internal passages be blocked by fine debris? ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-LMDTXlgZeV4.html Check out this video. He is another DIY'er and just like you explains things along the way. He replaced the bearings on a V10.

Hey man, not sure if you ever watch the channel Vice Grip Garage or not (The guy Derek is actually funny as fuck but he's also an amazing mechanic) but when I was watching one of his most recent videos, I immediately thought of you. You probably know everything he is going over in this video but he definitely offers up some tips that I think might help you. I know he's working on a big block chevy but at the end of the day, it's still a high output combustion engine.....anyways, the video is here......ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-GHqvyY4i1dw.html hope you can find some time to watch it.

Definitive answer: Buy a Lexus.

BMW*** typo

Any chance you still have the packaging for the replacement bearing you bought the first time? Is it possible the bearings were mislabeled?

Please help me, i have a 335i n54, low oil pressure at idle 15psi engine warm, checked camshaft beds are like new, oil pump like new, another one installed to be sure, still the same, connecting rod bearings like new, mileage!!!! 32,000 miles, real mileage!! the only thing left is a vacuum pump, sprays on the bottoms of the pistons, the correct pressure that should be at the start of a cold engine is less than 100psi, mine is 58psi ... have you ever encountered something like this?

21st century and BMW still doesn’t know how to make engines.

It happened to me in the past. I used a flexible, but strong enough wire and went trough every feeding oil channel in the engine block and head, crankshaft, etc. I was amazed what the wire brought out and the compressed air didn't... Every little obstruction matters a lot when it's about oil flow or quantity of oil/second! Anyhow, great work! I love this guy! I really like the way he approaches different situations.

Good video, but the bearings wont change shape with centrifugal forces. When you torque the rod the bearing becomes round :)

The first time an engine runs is crucial, it could be so many things wrong but, let me ask you this. • you probably used assembly lube, but to be sure did you? • did you primed the oil system before cranking it up? Did you reached full WOT pressure during the priming? If not, something was wrong, you should've never ran the engine and check your work and parts. • could you measure the length of the conrod bolts, did they all stretched the same +/- 0.5mm? • did you plastigauge the replacement bearings before final installation? •eventho the oil pump looked okay, were the oil passages for the bearings clean? If you push air thru them, was there any debris?