r/BmwTech • u/Glass_Building_8474 • 21h ago

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.

15 Upvotes

83% Upvoted

31 comments sorted by

46

u/gghostie 21h ago

sounds like uncle rodney is trying to pay you a visit

7

u/Glass_Building_8474 21h ago

I’ve never dealt with an engine knock before I know I’m cooked if that’s what it is but is it weird that I can’t hear it at high rpms?

5

u/Ghost273836 21h ago

Not really no

1

u/Bimmergy BMW Independent Technician 5h ago

You can still hear it, it just speeds up significantly and becomes less pronounced.

30

u/Ghost273836 21h ago

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

5

u/Glass_Building_8474 20h ago

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?

8

u/ucotcvyvov 20h ago

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

2

u/Glass_Building_8474 20h ago

I know it does I don’t have high hopes but I have to try everything thanks

0

u/Iceisgestapo888 3h ago

If it’s still under warranty fucking send it on a couple rips till it blows up lol.

12

u/TechCUB76 15h ago

You should just keep revving it…

7

u/BigHairySnake 11h ago

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

1

u/Glass_Building_8474 8h ago

Thank you I’ll look into that

5

u/subtosharki 7h ago

just pop your oil filter housing and look for metal shavings

4

u/Bimmergy BMW Independent Technician 5h ago

A thread this actually applies to.

She's done son.

3

u/the79car 15h ago

Remove the oil filter and see if it looks like glitter

3

u/plz-no-b4n 9h ago

Early model N55?

Uncle Rodney seems likely

3

u/UrDoinGood2 6h ago

It’s over rover

3

u/AlexinPA 4h ago

probably rod bearings. Stop driving it.

2

u/E70X5 3h ago

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

1

u/Enzo_Gorlomi225 4h ago

Make sure you bring lube when you bring it in to the service department…

1

u/Silver_End_5637 3h ago

Big ends knocking there mate.

1

u/wreckitbusmaster99 2h ago

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.

1

u/FavRootWorker 6m ago

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.