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Rod Bearing Failure
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06-29-2020, 07:03 AM | #1 |
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Rod Bearing Failure
Thought I'd share the wonderful situation I've ended up in and let people weigh-in on what went wrong.
Car is a 2008 335 RWD 6-speed, Sport model with the aux oil cooler. Mods are FBO; KW V3s, M3 sways, Michelin PSS, downpipes, ARM relocation intakes, VRSF intercooler, 335d coolant res, VRSF charge pipe, Tial BOV. Stock coils, index 10 injectors, pretty much stock everything else. I'm running the Stage 2 FBO 93 v5.1 octane MHD tune. No CELs, no weird codes, no misfiring, etc. Wastegates rattle but that's no surprise. Car has 180k kms on it (111k miles), nothing crazy, but getting up there. Anyway, took it out to an open lapping day on Friday. Get out there and gradually turn it up and up. Get about 3 laps in and started going WOT down the front straight, hitting about 185kmh, which is moving for the track I was on. Following the straight is a long-ish 100deg right hander that's taken at about 100kmh, followed by another straight to about 160kmh, then a bunch of series of lower speed rights and lefts (2nd gear). About 6 laps in I get the 'reduced engine power' message on the nav screen. I figured I'd overboosted or one of the turbos let go... so I took it easy and finished the lap (maybe 1.5km) and pulled into the paddock. What's that noise I hear? A squeak and rattle? Damn that turbo must be fucked I thought. I park the car and give it a little rev... nope... that's knock. Fuck. There was no oil pressure low indication, the oil was topped up, and the oil temp was mid-low on the gauge during all this. So I can only imagine the bearings weren't in the best shape to begin with, and they didn't like the 400ft lbs+ I was throwing at them. In any case, I'll post up some pics after I get a chance to pull the engine and tear it down. I'm hoping I can install another crank (assuming the journals are fucked) and new main and rod bearings. I'd rather not buy another engine, mine was otherwise mint and ran great. Thoughts... shared experiences... |
06-29-2020, 08:05 AM | #2 |
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There are probably low oil pressure shadow fault codes. When up in revs during high G turns and hard braking too there isn’t enough oil in the pan by the pick up tube so oil pressure drops. Happens to my own track car after I don’t know maybe 40-50 track days. There are few very good threads on the issue. With data. For n54/55 and n20 as well. All suffer the same.
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06-29-2020, 08:09 AM | #3 |
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I'll definitely see if there is some type of baffle I can install once I have the oil pan out.
I thought that might be the case too, so I scanned the codes. There are no shadow codes related to oil pressure, just 29F4/29F5 for cats, and 2FDB for crank sensor signal. |
06-29-2020, 08:53 AM | #5 |
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I have read that mhd v5 reduces knock sensitivity. May be best to get a custom tune or just run a safer map once you get it sorted out.
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06-29-2020, 09:01 AM | #6 |
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If you remove the sensor (bellow the starter) might be covered with what look like grey anti seize paste from mixture of oil and very fine metal particles. That is what I had on mine when I opened it up for rebuild. Others have proved with data of course that baffle on the oil pan doesn’t not help this particular engine with oil starvation. What scanning tool do you use for reading fault codes?
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06-29-2020, 04:04 PM | #7 | |
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What you experienced is most likely oil starvation due to pulling high G's consistently. Not sure if there's a Dry Sump system available for N54 Suggest you don't run V5 as mentioned due desensitised knock tables, read the same. Run 7.1 or higher. |
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06-29-2020, 09:09 PM | #10 | ||
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However, if one is tracking the car, I would think from proactive standpoint, I'd probably at least be running King Pin Rod Bearings & ARP bolts. While the ARP bolts aren't cheap, the rod bearings are by contrast very cheap insurance. https://www.ecstuning.com/b-king-par...r/cr222sv~kig/ $84.00 plus tax for all 6 cylinders. |
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06-30-2020, 12:47 AM | #11 | |
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Assuming you can do the labour yourself or get it done cheap Last edited by Saif2018; 07-01-2020 at 02:09 AM.. |
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06-30-2020, 02:29 PM | #12 | |
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$84 or not, it's hard to justify proactive rod bearing replacement on an engine where bearing failure is not common. The car didn't need an oil pan gasket or anything, so this would be a substantial amount of work for seemingly no reason. That being said, hindsight is 20/20 and I definitely see that it would have been worth the effort NOW.
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Anyway I will re-flash to 7.1 and see if the rod knock goes away. |
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06-30-2020, 04:30 PM | #13 | |
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07-01-2020, 02:04 AM | #14 | |
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Rod bearing failures can happen but I don't know anyone with rod bearing failure on n54, not even remotely heard of it. Rod bearing failure is more common on the E92 M3 with the V8. If the owner is tracking the car, he should definitely look into dealing with the oil starvation issue. What do you mean prohibits engine from starting? It doesn't have desensitised knock tables that's all I referred to. |
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07-01-2020, 07:30 AM | #15 | |
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I have personally done few with in the last year and I’m not even in the car repair business. So what should I say about it? Those desensitized knock tables didn’t cause the failure nor allow it to happen. If engine doesn’t start you won’t have knock. That’s the only way how you fix rod knock via tune. |
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07-01-2020, 10:07 AM | #16 | |
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If Rod bearing failure was common we would have heard it listed as common failure points. I don't think you understand the difference between not common and not happening. The former is what I said, as for can it happen yes. I didn't say Rod knock will be fixed via a tune, I was pointing out the fact it's not a good idea to run a tune with desensitised knock tables. Of course the owner can do whatever he wants. |
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07-01-2020, 11:08 AM | #17 | |
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In post #7 you advise OP to go with different tune. Wasn’t that you alluding tune will fix the rod knock? I think yes since you were directly replying to OP |
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07-01-2020, 04:06 PM | #20 | |
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V7 or V9 is better in my opinion. Rod bearing failure is not common on the N54 thats all I said. You can think whatever you want. Guess you like arguing and making assumptions so you can win arguments in your mind. That's just dumb. |
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07-01-2020, 06:09 PM | #21 | |
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07-01-2020, 10:07 PM | #22 |
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335i I just brought had engine replaced due to bearing knock.
190,000km on it. Not modified or anything. Always serviced on time. Who knows why bearing failed. Always change oil every 5000kms. And add extra oil when tracking. Usually 1 liter more but confirm with other people. Also oil pressure gauge wouldn't be a bad idea. higher weight oil is needed as well on track. But I think you may already know this. |
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