[sannouni]

Hi everyone, the new (to me) N55 2011 335i XDRive manual is making a very loud knocking sound (the reason it's not idling well is because the MAF is not installed, i'm actually surprised it's still running at all)

Here's a long-ish video that i made to capture the sound:

as you can see from the video, i tried disconnecting each coil, no change in the sound.

but when i disconnected the oil pressure switch, then start the engine, the noise gets louder and becomes more pronounced.

compression checks out OK on all cylinders.

i bought the car in its current state. i didnt find any metal shaving in the oil filter. but maybe i'm not looking close enough. would it be very fine metal shavings (if it was a rod bearing)??

any guidance and advice is appreciated

i have ordered the tools to remove the intake camshaft springs, injectors, chain timing tool which will allow me to open the top end and investigate further (if lifter or rocker, but i couldnt see anything obvious when i removed the valve cover)

the injectors were replaced 2 years ago.

the car was "tracked" a dozen times or so (according to the previous owner)

Any ideas?

[CoffeeBean]

You have the video set to where it won’t play until July 25 2:00pm.

[sannouni]

thank you for letting me know, i've been digging into the top end of engine for some time now, i couldnt find a bad lifter or broken spring.
i'm almost 100% sure that it's cylinder 6 rod bearing.
the way i found out was to remove the spark plugs, rotate the engine so that the piston that i'm testing is travelling downwards, then use a long 1/4 inch extension, insert into the spark plug hole until it touches the top of the piston, and tap the extension with a rubber hammer, the sound was clear, the piston had to travel extra distance (less than 1mm) but it was enough to make a thud that was very different from the other pistons tested.
I'm going to try and make a video of that and post it here, and i will make sure that it can be viewed by everyone.

[Dynamics99]

Originally Posted by sannouni

thank you for letting me know, i've been digging into the top end of the engine for some time now, i couldn't find a bad lifter or broken spring.
i'm almost 100% sure that it's a cylinder 6 rod bearing.
the way i found out was to remove the spark plugs, rotate the engine so that the piston that I'm testing is travelling downwards, then use a long 1/4 inch extension, insert into the spark plug hole until it touches the top of the piston, and tap the extension with a rubber hammer, the sound was clear, the piston had to travel extra distance (less than 1mm) but it was enough to make a thud that was very different from the other pistons tested.
I'm going to try and make a video of that and post it here, and i will make sure that it can be viewed by everyone.

Most likely spun bearing with that travel from the 1/4 extension. Currently rebuilding mine after my mistake (Made a post about it). If you have space to rebuild at home pull the motor out and disassemble the bottom and check the scoring marks on the rod 6 journal. Take the crankshaft out and to a machine shop and see if it needs a regrind or polish.

[sannouni]

Dynamics99 great thank you for the information, can you share a link to your post please?

i dont have space at home (as you can see from the video, the car is currently in an underground garage) so i'll tow it to a garage that i trust, and have them disassemble the bottom end and show me what cylinder 6 bearing and rod journal look like

question: the connectting rod bottom bracket would be out of round due to the piston beating on it. but realoem is not showing a seperate part number for it, what do you do in this case? buy a used connecting rod and just use the bottom of it?

Here's the video i was talking about:

[Dynamics99]

Originally Posted by sannouni

Dynamics99 great thank you for the information, can you share a link to your post please?

i dont have space at home (as you can see from the video, the car is currently in an underground garage) so i'll tow it to a garage that i trust, and have them disassemble the bottom end and show me what cylinder 6 bearing and rod journal look like

question: the connectting rod bottom bracket would be out of round due to the piston beating on it. but realoem is not showing a seperate part number for it, what do you do in this case? buy a used connecting rod and just use the bottom of it?

Here's the video i was talking about:

Hmm,

If you want you could check it yourself before you take it to a garage. Drop the subframe and the oil pan and the pickup tube. Then see if the bearing has spun. I mean you could go get another used connecting rod or go forged depending on budget.

Connecting rods were installed as a set from the factory as they are balanced. Someone would have to enlighten me if another used connecting rod can be used or would OP would have to balance that to match his original set.

https://www.e90post.com/forums/showthread.php?t=2027171

Here you go.

[PhaceN52]

Originally Posted by sannouni

question: the connectting rod bottom bracket would be out of round due to the piston beating on it. but realoem is not showing a seperate part number for it, what do you do in this case? buy a used connecting rod and just use the bottom of it?

If I recall correctly they are cracked, so you can't just use another bottom rod cap but the whole rod instead, but let's wait for a confirm.
as Dynamics99 says they're balanced as a set, don't know what's the weight discrepancy you can go with

[sannouni]

thank you for the responses.
if the bottom caps are "out of round" due to the knock. what would you do? is there a procedure for that (replace rods, machine shop can do something) ? i'm just trying to prepare mentally for the work ahead.
also, if was to remove the pan (it's an XDrive so a whole lot more fun to access the access the rod bearings) are the wrist pins accessible from there? i doubt it (that's if i wanted to swap out the affected rod)

[Dynamics99]

Originally Posted by sannouni

thank you for the responses.
if the bottom caps are "out of round" due to the knock. what would you do? is there a procedure for that (replace rods, machine shop can do something) ? i'm just trying to prepare mentally for the work ahead.
also, if was to remove the pan (it's an XDrive so a whole lot more fun to access the access the rod bearings) are the wrist pins accessible from there? i doubt it (that's if i wanted to swap out the affected rod)

I would say, first check if the bearing has spun on cylinder 6. If it has spun then button the engine back up and take it to a garage. The XDrive is a bit more work. Some guy on youtube has done it. The wrist pins slide between the small connecting rod end and the piston. They will not be accessible from the bottom side. You will have to remove the head and remove the piston from the top out. Some people on the forums have done it with the engine but it's a pain since you need to remove the turbo drain lines and coolant lines.

I most likely going forged connecting rods so I will be getting a whole new set. The guy on youtube just yolo'd and pick the best looking used connecting rod and it still works to this day.

[sannouni]

Dynamics99 thank you for the response. i have seen this video some days ago, and i was wondering if the car ran with a swaped #6 piston.

i have a space restriction, the car is currently in an underground garage, so i'll have to tow it to a place where i can rent a hoist for a week or so to do the work (bring my own tools), but i want to do some more homework before then to try and reduce dead-end problems that might come up.

in terms of tools, i've been working on BMWs for over 12 years so far, from suspension, to transmission (auto and manual) to the various known failures in E46s and E90s... so i'm not worried about the special sockets (e-torx etc.), i will review them anyway to make sure i got what's needed.

so thank you for the list you had on your thread (linked above) about the orings/gaskets and bolts that will need replacing, it's helpful.

This is an XDrive, i've previously replaced axle shafts on E46 and E90s, sometimes they get stuck in the hub, so i dont want to face that when the car is up and i'm paying rent the hoist, i'll attempt to remove them from the hub (and lube and put back) prior to the big work.

i'll also do a check to make sure i have the extensions etc needed for the work (example, steering column bolt, head bolts if i need to remove the head to replace pistons, etc), and calibrate the torque wrenches (1/4, 3/8, and 1/2 drives), and have an angle gage on hand (only 1/2 drive, i hope it will suffice)

engine support question, does the towing attachment fit on the top of the engine? or is there a speacial attachment that bolts next to the oil filter housing? and then if i decide to also pull the head (if rod bearing out of round), will i still be able to attach the subframe from the bottom and remove the engine support from the top? it looks like the engine mounts are untouched in the procedure, so i think it's a yes but any input is appreicated)

i will come back with more questions. thanks for any inputs.

[sannouni]

The reason for the following is to have a better guess, if the crank is toast, or not yet... again just a guess... I'd appreciate any opinions:

I asked the previous owner about what was done after the knock started. I asked if they pushed it, and if the noise got worse...
The response is that the noise never got worse, once it started, it stayed the same... but the car was driven for about 45 minutes at 80km/h (around 50mph) with that knock (the one you hear in the video in the first post). According to the previous owner, the engine was not "pushed".

Now I'm doubting if the crankshaft is good ... I understand that there is no way to know for sure until I gain access to the cylinder #6 journal and inspect it...

I'm trying to weigh my options here... should I pull the engine out? Or should I go the oil pan route...

ACL bearings and a bunch of 1 time use bolts/orings/pan gasket are making their way to me by next week (FCP Euro). Now I need a game plan.... bottom or engine out? What do you think?

"Bottom" approach is easier for me to arrange. But would the information above force me to change ? Its a Delima....

[Dynamics99]

Originally Posted by sannouni

Dynamics99 thank you for the response. i have seen this video some days ago, and i was wondering if the car ran with a swaped #6 piston.

i have a space restriction, the car is currently in an underground garage, so i'll have to tow it to a place where i can rent a hoist for a week or so to do the work (bring my own tools), but i want to do some more homework before then to try and reduce dead-end problems that might come up.

in terms of tools, i've been working on BMWs for over 12 years so far, from suspension, to transmission (auto and manual) to the various known failures in E46s and E90s... so i'm not worried about the special sockets (e-torx etc.), i will review them anyway to make sure i got what's needed.

so thank you for the list you had on your thread (linked above) about the orings/gaskets and bolts that will need replacing, it's helpful.

This is an XDrive, i've previously replaced axle shafts on E46 and E90s, sometimes they get stuck in the hub, so i dont want to face that when the car is up and i'm paying rent the hoist, i'll attempt to remove them from the hub (and lube and put back) prior to the big work.

i'll also do a check to make sure i have the extensions etc needed for the work (example, steering column bolt, head bolts if i need to remove the head to replace pistons, etc), and calibrate the torque wrenches (1/4, 3/8, and 1/2 drives), and have an angle gage on hand (only 1/2 drive, i hope it will suffice)

engine support question, does the towing attachment fit on the top of the engine? or is there a speacial attachment that bolts next to the oil filter housing? and then if i decide to also pull the head (if rod bearing out of round), will i still be able to attach the subframe from the bottom and remove the engine support from the top? it looks like the engine mounts are untouched in the procedure, so i think it's a yes but any input is appreicated)

i will come back with more questions. thanks for any inputs.

My towing attachment kind of fits. It does not thread in all the way but hey it atleast helped with the engine being removed. I used a harbour freight engine crane/hoist with their leveler. One end to the towing hook and the other hooked into the starter hole.

I left the engine mounts in the car. Only unscrewed the engine mount top nut. Then I disconnected the engine mount support bracket. Passenger side has like 4 bolts I think which were a pain. Wobble extension will help.

Downpipe removal is needed. Make sure you drench the downpipe flange to the exhaust in PB Blaster. My nuts came off nicely even though they were rusted.

[Dynamics99]

Pull the motor. I think the crank can be saved. Yank the motor out and strip it down. You don't have to take the camshafts off. You can leave the head alone and just walnut blast it. When you rebuild it I would ensure the oil squirters at the bottom of the cylinder wall are free of any particles.

Send a picture of the score marks on the crankshaft. It's a crankshaft after all. It all comes down to the measurements. There should be score marks. Take it to a shop and have them say the crank is toast or is it worth regrinding.

[whyzee125]

Another N55 bites the dust