Strange knock/thump noise from passenger side

Hoping to get some info from the M-hivemind here. Video is here, which I sent to my BMW mechanic also (hence my talking), but he's quite busy so figured I'd gather other opinions. Noticed it that morning but was in a rush and I was inside the car and this is a pretty noisy engine and it was cold, so I figured it was fine, drove it a while, came home, started it up to run an errand, and when I got out to grab something from the trunk, realized this was a bad noise. Video starts with driver wheel well noise, which is totally normal and the loud lifter/injector noise common to this engine, but when I move to the passenger side kidney grille (and later open the hood), it's very clear what the noise I am talking about is.

It's a fairly pronounced and slow thunk/slap noise. Appears to be coming out of the passenger side valve cover area. I popped the oil cap off for a second just to see if it would make the noise louder, but it did not (I was careful not to cover myself in oil ).

Some history on the car:
Rod bearings done roughly 10k ago with Malek @ MRF. No weird noises since then until now, so hopefully it is unlikely to be the rod bearings, since that would be a VERY short time. 127,000 miles. Hoping it is not main bearing as I am considering selling soon.

Plugs are all new, one coil has been replaced, but no codes for a while. Valve covers are entirely brand new, throttle actuators are still good (replaced 2 years ago), transmission has been fully serviced, driveshaft rebuilt. Not that any of that is likely relevant, but that's really the universe of work that's been done here.

The noise (as I mutter in the video) is RPM-dependent, but it seems slower than I'd expect for a knock, but I am far from an expert on this engine platform. Any thoughts are welcome. Thanks!

Edit:
I'm changing my order of troubleshooting...it is RPM dependent as you said. Here's my best guess. Best to worst case below:
I would highly recommend pulling your A/C accessory belt off the engine (A/C, Power Steering) and running it again, just idle it like you did for your video (it is the belt on the passenger side of the engine). If the noise is gone, you can narrow it down to one of those items. Also check your belt for a really bad spot that might knock on each roation.
To get the belt off remove the cap off the tensioner pully and put a socket and your longest wratchet or very long box wrench on it and pry it away from the tension to release the load and it will let you slip the belt off, then fully remove the belt. Before you do make note of the PS pump rotation. Some models are clockwise (wrapped over) and others are counter clockwise (wrapped under) the pully on the pump.

If the noise persists, with the belt off, I will go back to my first fear of a broken valve spring.

A main bearing wont sound like that and won't be only on one side. A vanos gear could also be a problem, but start simple first. Good luck, keep us posted.

man, I sure hope that's not rock knock, Malek at MRF is very very good...the product from VAC...not so much. I hope you didn't get a fawked shipment of bearings.

Cheers,
TX

TX wrote

Edit:
I'm changing my order of troubleshooting...it is RPM dependent as you said. Here's my best guess. Best to worst case below:
I would highly recommend pulling your A/C accessory belt off the engine (A/C, Power Steering) and running it again, just idle it like you did for your video (it is the belt on the passenger side of the engine). If the noise is gone, you can narrow it down to one of those items. Also check your belt for a really bad spot that might knock on each roation.
To get the belt off remove the cap off the tensioner pully and put a socket and your longest wratchet or very long box wrench on it and pry it away from the tension to release the load and it will let you slip the belt off, then fully remove the belt. Before you do make note of the PS pump rotation. Some models are clockwise (wrapped over) and others are counter clockwise (wrapped under) the pully on the pump.

If the noise persists, with the belt off, I will go back to my first fear of a broken valve spring.

A main bearing wont sound like that and won't be only on one side. A vanos gear could also be a problem, but start simple first. Good luck, keep us posted.

man, I sure hope that's not rock knock, Malek at MRF is very very good...the product from VAC...not so much. I hope you didn't get a fawked shipment of bearings.

Cheers,
TX

Given the speed of the noise, I spoke with him and he said it sounded 100% like the chain tensioner. Makes sense as recently I have been hearing a bit of a clatter on cold starts for a second that sounds like chain takeup. I'll check the belt this weekend. Thanks!

https://www.m3post.com/forums/showpost.php?p=27525109&postcount=206

Check this thread , pulleys and belts might be the culprit.

Well, took it into Performance Technic in Fremont, which is a great shop, and they racked it up and took a long listen and diagnosed it as rod knock. Stethoscoped the bottom end and it was VERY loud down there. Not sure what to do. No chance am I going to pour the money to rebuild the engine or replace it on a 2008 with 130k miles, when I was already considering selling.

Will reach out to Malek and see what the next step is, unfortunately.

fatalelement wrote

Well, took it into Performance Technic in Fremont, which is a great shop, and they racked it up and took a long listen and diagnosed it as rod knock. Stethoscoped the bottom end and it was VERY loud down there. Not sure what to do. No chance am I going to pour the money to rebuild the engine or replace it on a 2008 with 130k miles, when I was already considering selling.

Will reach out to Malek and see what the next step is, unfortunately.

Report back with any findings.

I hope everything goes well, Malek is also a stand up guy so I'm sure between the three of you, something will be resolved.

Vuu wrote

Report back with any findings.

I hope everything goes well, Malek is also a stand up guy so I'm sure between the three of you, something will be resolved.

Malek is great, obviously. He offered to do a teardown and obviously take care of it under warranty if rods (but said he has not had to do that once), he says it's very difficult to take seriously that the shop knows it's rod knock without a teardown. I tend to agree with that. He gave me his personal number and said to call him whenever and he'll make taking care of whatever I choose to do a priority. Reminds me why I went with him for the bearings, great customer service.

The problem is I am in the Bay and Malek is not, my family is in LA so I took it to him while visiting for the bearings, but now I would have to ship/have it towed to him, which makes the math different.

I'm gonna get a quote on just selling it as is, see what the deal is (not to someone who plans to drive it, but a place that knows what they're getting, like a wholesaler), and if it's good enough, take it, if not, probably ship it down to Malek although most of the options (unless it's something odd and innocuous) are gonna make the engine toast anyway, so I'm apprehensive about putting more money into it.

Well, update for anyone still interested, Performance Technic finally got into it - rod bearings are fine (some light scoring, likely from whatever else is throwing metal out) but are only slightly out of spec. What is not fine is that the oil pan has light debris in it. Something else is coming apart. So the engine is on its way to toast, either main bearing or something else. They checked all the non-full-engine-teardown components (oil pump, chain tensioner, etc.), and no joy.

It gave it a good run, and screamed all the way to 140k miles, but seems like it's time to figure out if it's worth it to replace/rebuild the engine (probably not) or say goodbye and send it to car heaven. I'm heavily leaning towards a new car as my budget has changed considerably from when I got this one, and as much as I love the E9X platform I think it's time for the next 4 wheeled adventure.

fatalelement wrote

Well, update for anyone still interested, Performance Technic finally got into it - rod bearings are fine (some light scoring, likely from whatever else is throwing metal out) but are only slightly out of spec. What is not fine is that the oil pan has light debris in it. Something else is coming apart. So the engine is on its way to toast, either main bearing or something else. They checked all the non-full-engine-teardown components (oil pump, chain tensioner, etc.), and no joy.

It gave it a good run, and screamed all the way to 140k miles, but seems like it's time to figure out if it's worth it to replace/rebuild the engine (probably not) or say goodbye and send it to car heaven. I'm heavily leaning towards a new car as my budget has changed considerably from when I got this one, and as much as I love the E9X platform I think it's time for the next 4 wheeled adventure.

any pictures of thr rod bearings ?

atopa2002 wrote

any pictures of thr rod bearings ?

Nah, I didn't ask. They're lightly scored but they've been replaced very recently. The rod bearings aren't the issue here - I had them done w/ Malek @ MRF about 5,000 miles ago. They're within reasonable tolerance, they gauged them and also took them out for inspection. Something else inside the engine is causing the knocking and is coming apart leaving metal in the oil (which I do have pictures of, but can't be bothered to download, reupload, and put in here). It's a decent amount of metal shavings.

fatalelement wrote

Well, update for anyone still interested, Performance Technic finally got into it - rod bearings are fine (some light scoring, likely from whatever else is throwing metal out) but are only slightly out of spec. What is not fine is that the oil pan has light debris in it. Something else is coming apart. So the engine is on its way to toast, either main bearing or something else. They checked all the non-full-engine-teardown components (oil pump, chain tensioner, etc.), and no joy.

It gave it a good run, and screamed all the way to 140k miles, but seems like it's time to figure out if it's worth it to replace/rebuild the engine (probably not) or say goodbye and send it to car heaven. I'm heavily leaning towards a new car as my budget has changed considerably from when I got this one, and as much as I love the E9X platform I think it's time for the next 4 wheeled adventure.

Man I'm sorry to hear.

But, if you miss it that much in the future, you can always come back!