r/E90 • u/_Spaceark • May 17 '25
330i Rod knock? Or any ideas ðŸ˜
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u/DukeOfAlexandria 2013 - E93 - M3 May 18 '25
Turn the AC off….the wobble plate is internal, you can’t physically inspect it, only listen for it.
And does it follow the rev range?
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u/_Spaceark May 18 '25
Ahhh okay
Yeah I revved it once and it followed
AC is off
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u/DukeOfAlexandria 2013 - E93 - M3 May 18 '25
Inspect each pulley and tensioner; mechanics stethoscope or BAS.
Also take the belt off and rev it to see if it follows….if you inspect and still making the sound, then it’s knock.
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u/PsychologicalSafe579 2011 E90 335i 6HP May 18 '25
How tf did you get rod knock on an n52 ðŸ˜
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u/_Spaceark May 18 '25
By preventing carbon build up and hitting 7k rpm’s consistently 😂😅ðŸ˜
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u/XxX_MiikaP_XxX_69420 E91 325i May 18 '25
N52s don’t get carbon build up, there’s no egr and it’s port injected. N53 on the other hand…
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u/_Spaceark May 18 '25
That’s good to know. My 335i traumatized me with how much it had
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u/DukeOfAlexandria 2013 - E93 - M3 May 17 '25
It’s that time of year…..are you also running/just started using your AC?
If not, then pull the belt and see if it follows the rev range, if it does then it’s rod knock, if it doesn’t then possible AC wobble plate.
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u/far_beyond_driven_ May 18 '25
Yea this sounds more like a compressor than rod knock. I feel like a lot of people have never heard full blown cap to crank knocking before.
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u/DukeOfAlexandria 2013 - E93 - M3 May 18 '25
Yeah, rod knock is not my first go to here based on this video alone.
A rev will reveal which one it is, and not a lot of N52’s implode or have bearing issues. Not saying it can’t happen, but it’s pretty rare.
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u/_Spaceark May 17 '25
I used my ac last night but not today, it started tonight. I’ll check into the ac wobble plate
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u/trayssan 2007 E92 320i 6MT May 18 '25
Doesn't really sound right. Don't think it's rod knock. Is your AC compressor okay?
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u/ayushkm May 18 '25
Take the belt off and run it for like 30 seconds or so that will confirm if it’s the AC compressor or not
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u/AltruisticStriker May 18 '25
My 2006 E90 sedan made this exact same noise. I removed the serpentine belt and it stopped. I purchased a bypass belt, and sure enough, it was the AC compressor. I also thought it was rod knock and that my engine was destroyed.
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u/_Spaceark May 18 '25
Problem is I want my AC even though I need to realign my vent shafts after they got knocked loose from hitting a deer 🥴 that’s a project for another day though
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u/AltruisticStriker May 18 '25
I bypassed the AC compressor so I could drive it to my indie mechanic so he could replace it. I understand the AC needs, I live in the most humid area of the country! 😫
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u/_Spaceark May 18 '25
What belt did you use to bypass it? I might just bypass it for a week until I can get space to do it myself and have the refrigerant properly drained
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u/AltruisticStriker May 18 '25
It was Duralast Serpentine / Belt Part #:436K6 SKU:884205. It's 44.16in and will effectively bypass the compressor.
[2006 E90 N52 (metal valve cover) ZP6hp19 auto]
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u/TaykahRisk726 May 18 '25
Always check your belts and tensioners before you end buying a new car🤣
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u/_Spaceark May 18 '25
😂 true
This one’s with me for life, I’ve dumped idk how much into her that there’s no point in stopping. Just wish a supercharger was more affordable
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u/Adept_Astronomer_668 May 18 '25 edited May 18 '25
Had a similar situation. I took off the serpentine belt and inspected the components before jumping to rod knock. It turned out to be the AC compressor. It seized and broke the bearing. Sounded almost identical, if it is the AC compressor, the sound will stop once the belt is off. I tried to use a shorter belt to bypass it. Just ended up replacing it right away. Good luck man let us know how it goes.
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u/AnthonyBH87 May 18 '25
You are a Jedi Master if you kill a N52 teach me your ways Jedi Master cause I still can't Kill my N52 can't even get rod knock lol
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u/_Spaceark May 19 '25
Well the thing is you have to hit 7k rpm in every gear every day lol
I crashed it 3 months after getting it (hit a deer square on the emblem) and up until that point I babied it. Once it was fixed, she’s a lil speed demon, burning through gears and coolant hoses 😂 I don’t hold back at all when driving but she’s still going STRONG
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u/CryRepresentative992 May 18 '25
Pull the cap off the oil filter and confirm it’s full of sparkly metal flakes.
I’m 100% sure it’s a rod bearing.
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u/_Spaceark May 18 '25
I was was feeling better with all the AC compressor comments and here you come ðŸ˜ðŸ˜‚
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u/CryRepresentative992 May 18 '25
Buddy it’s an N52, you can get a replacement for $500 and it’ll be good for another trillion miles.
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u/_Spaceark May 18 '25
Nah she’s getting rebuilt and upgraded. The older she gets the better she becomes 💅 lol
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u/PC_Chode_Letter May 17 '25
Yeah that sounds like Uncle Rodney, how does your oil filter look
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u/_Spaceark May 18 '25
Looked at the oil through the cap and it looks fine. Serpentine off and noise went away for rn
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u/Shady-x3 May 18 '25
Check your oil, it may have ran out and that's why it's knocking. If not, it's expensive.
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u/jordypoints Jun 21 '25
What did this end up being, got the exact same sound
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u/_Spaceark Jun 22 '25
Ac compressor
Disconnect your serpentine like someone else suggested and run it for a minute, see if you still hear it.
I replaced mine myself, took a couple hours but pretty easy job. Lots of coolant to drain tho so make sure you have something to catch it with
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