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      11-23-2020, 07:43 AM   #1
DG330
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N20 knocking - rods or torque converter VIDEO

Hi,

Noticed my N20 makes a slight knock but only when fully warmed up. The knock is not present at start up or when warming up. Only appears at 80-90C

It's comes on at 1k rpm and can only be heard from underneath the car or inside the cabin.

I've heard that it could be the torque converter being out of place and needs turning?

BMW did the chain a year ago and said the oil was fine when removing as sometimes if the oil pump fails it causes the oil to go funny. Wasn't sure what they meant, but during the strip down it was all okay.

Any thoughts?

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      11-24-2020, 05:04 PM   #2
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      12-05-2020, 10:25 AM   #3
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Sounds like early rod knock. but get a stethoscope and place it on the block whilst you rev it if its louder then it'll 99.9% be rod knock
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      12-05-2020, 10:30 AM   #4
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Quote:
Originally Posted by navardi View Post
Sounds like early rod knock. but get a stethoscope and place it on the block whilst you rev it if its louder then it'll 99.9% be rod knock
Yeah I done this, but couldn't hear anything when under it. Checked both block/sump from underneath and gearbox.

It's currently got 0w30 in, at the next change I'll put 0w40 in to see if it helps.

I don't get any knocks at start up or switch off which comes with rod knock.
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      12-07-2020, 02:23 AM   #5
DG330
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So after thinking about this and listening to it more it only happen when at full temp and
Between 1500-2200rpm.

I've used a hearing device on the sump and gearbox and can't work out what it is.

Could this be an imbalance on the harmonic balancer?

I am also considering changing the rod bearings, but wondering if there is an easy way to do this as mine is xdrive. Also, is there an easy way of getting the oil pump out without having to remove the chain assembly?
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      12-11-2020, 03:33 AM   #6
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Another video



Phone is underneath front engine and it's less apparent and the knock can not be heard at 3-4K rpm.

Any thoughts?
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      12-15-2020, 04:16 PM   #7
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      12-15-2020, 04:38 PM   #8
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Quote:
Originally Posted by DG330 View Post
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Another video



Phone is underneath front engine and it's less apparent and the knock can not be heard at 3-4K rpm.

Any thoughts?
Sounds like my N20 in the low RPM ranges or idle. I'm sure others are just as noisy.
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      12-15-2020, 05:15 PM   #9
DG330
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That's relieving. It's strange though as it raises and falls with the rpm.

Is yours the same when hot?
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      12-15-2020, 06:59 PM   #10
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Sounds fairly normal, possible some waste gate rattle or motor mounts are getting worn, but I doubt it's a knock.
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      12-15-2020, 07:05 PM   #11
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This is mine on a cold start, but warm it's not quite as loud.

https://f30.bimmerpost.com/forums/sh....php?t=1773400
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      12-16-2020, 05:51 AM   #12
DG330
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Thanks for the replies.

The noise I'm talking about is kinda like a knock or imbalance wobble. It's most apparent on this video at 14-30 seconds. There's a noise just after deceleration.



It's quite hard to hear
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      12-16-2020, 06:22 AM   #13
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Quote:
Originally Posted by DG330 View Post
Thanks for the replies.

The noise I'm talking about is kinda like a knock or imbalance wobble. It's most apparent on this video at 14-30 seconds. There's a noise just after deceleration.



It's quite hard to hear
I feel my n26 was noisy and had a ticking sound (injectors), but it did not sound like this when I stepped on the gas.
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      12-16-2020, 06:30 AM   #14
DG330
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Thanks for confirming.

This noise is only apparent from underneath rear of the engine towards the gearbox and only when at operating temp.

Thought it might be torque converter so I re-torqued the bolts, but no difference.

BMW only changed the oil and filter in September and didn't mention anything. Also they did the TC in December 19 and no mention of problems which they said they would check due to the broken chain guides.

Might pull the oil to check it, but seems wasteful as it's only covered 1k miles. I've checked the filter and couldn't see anything. Also used a magnet, I'll check it again though.

Another thing I was thinking is could it be the oil pump counter balance?
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      12-16-2020, 09:48 AM   #15
DG330
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I pulled my oil filter and put some oil on white paper and could see some shiny specks.

With so many moving parts I would expect there to be some and on a 100k engine. However, I do wonder if the two could be related. Any thoughts on this?

I'll test it again when I can and post a picture/video.

I'll drop the oil when there's a break in the weather. I would drop the sump, but it's quite a big job on the X drive during winter. So might have to wait until spring/summer to inspect the rod bearings.
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      12-16-2020, 01:51 PM   #16
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Quote:
Originally Posted by DG330 View Post
I pulled my oil filter and put some oil on white paper and could see some shiny specks.

With so many moving parts I would expect there to be some and on a 100k engine. However, I do wonder if the two could be related. Any thoughts on this?

I'll test it again when I can and post a picture/video.

I'll drop the oil when there's a break in the weather. I would drop the sump, but it's quite a big job on the X drive during winter. So might have to wait until spring/summer to inspect the rod bearings.
That's scary, have you had the timing chain fixed yet? Would recommend to stop driving, get an oil sample and have a good independent shop take a look.

Metallic specs are not good regardless of mileage.

If you open the oil cap, can you wiggle the timing chain with a screwdriver? Does it look loose?
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      12-16-2020, 06:03 PM   #17
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Quote:
Originally Posted by DG330 View Post
So after thinking about this and listening to it more it only happen when at full temp and
Between 1500-2200rpm.

I've used a hearing device on the sump and gearbox and can't work out what it is.

Could this be an imbalance on the harmonic balancer?

I am also considering changing the rod bearings, but wondering if there is an easy way to do this as mine is xdrive. Also, is there an easy way of getting the oil pump out without having to remove the chain assembly?
I'll be interested in finding out what comes from this, I have a very similar noise coming from my N55 engine on an F32 RWD. It's in with the dealership now and of course, they recommended a new engine at 75K miles. Here is a video of my engine idling at 2K RPMs where the knock is loudest.

https://youtu.be/I0nsGIlT3z8

Out of curiosity, are the rod bearings easy to replace once the oil pan is removed?
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      12-18-2020, 04:54 PM   #18
DG330
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Hi,

So I checked the oil again today on paper and could see some tiny flecks, but not a lot. I filmed the following video of the oil filter housing. There's some flecks, but it doesn't look bad.

Regarding my knock it's very hard to hear and can only be heard from underneath. Can't hear it at the top of the engine. It's quite faint, I'm starting to think it might be gearbox or torque converter as I can some funny noises when it's hot and in reverse.

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      12-18-2020, 05:00 PM   #19
DG330
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Quote:
Originally Posted by Phoenix704 View Post
Quote:
Originally Posted by DG330 View Post
I pulled my oil filter and put some oil on white paper and could see some shiny specks.

With so many moving parts I would expect there to be some and on a 100k engine. However, I do wonder if the two could be related. Any thoughts on this?

I'll test it again when I can and post a picture/video.

I'll drop the oil when there's a break in the weather. I would drop the sump, but it's quite a big job on the X drive during winter. So might have to wait until spring/summer to inspect the rod bearings.
That's scary, have you had the timing chain fixed yet? Would recommend to stop driving, get an oil sample and have a good independent shop take a look.

Metallic specs are not good regardless of mileage.

If you open the oil cap, can you wiggle the timing chain with a screwdriver? Does it look loose?
Yeah I've had the TC replaced and also the done the valvetronic as it completely failed in min lift. Actually, the metal could be from that as everytime I locked and unlocked it would click a lot.

TC guides were broken up, bmw inspected the oil and pan and said there were no concerns when replacing it.
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      12-18-2020, 05:07 PM   #20
DG330
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Quote:
Originally Posted by F32Huncho View Post
Quote:
Originally Posted by DG330 View Post
So after thinking about this and listening to it more it only happen when at full temp and
Between 1500-2200rpm.

I've used a hearing device on the sump and gearbox and can't work out what it is.

Could this be an imbalance on the harmonic balancer?

I am also considering changing the rod bearings, but wondering if there is an easy way to do this as mine is xdrive. Also, is there an easy way of getting the oil pump out without having to remove the chain assembly?
I'll be interested in finding out what comes from this, I have a very similar noise coming from my N55 engine on an F32 RWD. It's in with the dealership now and of course, they recommended a new engine at 75K miles. Here is a video of my engine idling at 2K RPMs where the knock is loudest.

https://youtu.be/I0nsGIlT3z8

Out of curiosity, are the rod bearings easy to replace once the oil pan is removed?
Sorry to say it, but your sounds worse than mine. Check all my videos and you'll hear that it disappears at 3k rpm and above. I've had rod knock before on a Mitsubishi and I could hear it at idle and all rpms and it was bad.

Regarding doing the bearings there's videos on YouTube for N55

Yours should be relatively easy. Drop the subframe - support engine from top. Drop it by 10cm and lock flex plate, remove pan, remove oil pump (think just strainer and oil chain bolt, will need to take tension if chains using Allen key)

Then use plastigauge and get tolerances from bmw along with correct bearings. Ista will give you a guide.

Lots of assembly lube, new oil and filter, prime the engine (disconnect coil packs and injectors) crank 4/5 times to build oil pressure and lubricant system. Make sure oil pressure light goes out. There's more on priming online. Hope for the best that it's worked, if the platigauge readings come in ok you should be good.
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      12-11-2022, 03:40 PM   #21
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Quote:
Originally Posted by DG330 View Post
Thanks for the replies.

The noise I'm talking about is kinda like a knock or imbalance wobble. It's most apparent on this video at 14-30 seconds. There's a noise just after deceleration.



It's quite hard to hear
I know is and old post, but i have the same sound on my n20, do you fixed it?
Thanks!
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