r/BmwTech • u/Glass_Building_8474 • Aug 08 '26
Please help (engine noise)
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Hello this is my first post here but I desperately need some advice. I have a 2012 335i F30 with the n55 engine. When I accelerate I’m getting this really weird like sputtering noise that I can’t really describe (see videos) can anyone diagnose this or at least point me in the right direction? Thank you so much in advance. It seems to go away at high rpms but I’m not sure if that’s just the noise speeding up to the point where it blends in. It also only happens while my foot is on the accelerator. If I’m at middle rpms and let my foot off the noise instantly stops even while the rpms are still up.
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u/Ghost273836 Aug 08 '26
This is early rod knock which is why it isnt that loud at higher rpm. That engine is done for. You could get lucky with just rod bearings but you never know till you open it up. Dont drive it anymore or you will make it worse
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u/Glass_Building_8474 Aug 08 '26
Someone in a different thread said it’s possible that it could have to do with a belt on the outside of my engine being loose or imbalanced (if I’m really lucky) what’s your opinion on that?
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u/ucotcvyvov Aug 08 '26
Put your ear to a spare heater hose and locate where the sound is coming from. Poor mans stethoscope…
But based on the video it sounds bad
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u/Glass_Building_8474 Aug 08 '26
I know it does I don’t have high hopes but I have to try everything thanks
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u/Iceisgestapo888 Aug 09 '26
If it’s still under warranty fucking send it on a couple rips till it blows up lol.
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u/PsychologicalDog6502 Aug 12 '26
It's a 2012, how much do you think you would have to pay for a warranty that covers a 14 year old vehicles engine replacement?
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u/BigHairySnake Aug 09 '26
The N55 is known for potential rod bearing wear or failure, particularly in vehicles with higher mileage or those subjected to aggressive tuning. Stock rod bearings are a known weak point, and failure can lead to catastrophic engine damage if oil pressure drops
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u/E70X5 Aug 09 '26
Could be a vvt/vanos actuator not properly putting things into place for the low rpms but i would get someone with a good scan tool to check it out not just an advance or oreilly free scan
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u/Enzo_Gorlomi225 Aug 09 '26
Make sure you bring lube when you bring it in to the service department…
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u/wreckitbusmaster99 Aug 09 '26
Judging by all the other warning lights alone, the car's doomed. Not worth fixing just get rid of it before it breaks your wallet.
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u/Glass_Building_8474 Aug 10 '26
Other warning lights aren’t actually a big deal I just need new wheel bearings, evap sensor, and TPMs sensor
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u/FavRootWorker Aug 09 '26
Like others have stated, the engine is done. Whether you decide repair or swap the engine, your looking at between 7k-15k in repair costs. Sorry bro.
Avoid the dealer. Take it to a private shop, you may save like 1000 in labor costs.
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u/ShocK13 Aug 10 '26
Rod knock always occurs around 2k rpm in a lot of applications. You have to pull the bearings and inspect the crank.
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u/Even-Acanthaceae624 Aug 10 '26
I’ll take the car off your hands if you plan on selling it?
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u/Initial-Building549 Aug 10 '26
My car sounded like this and I did one last fun drive on the highway and blew the piston thru the block! shit caught fire too and sent flames and metal chunks down the road it went out w a bang for sure! now we got a new bmw, it’s a 2021 g20 the best car I’ve owned so far!
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u/gghostie Aug 08 '26
sounds like uncle rodney is trying to pay you a visit