BMW n52 low pitch knocking noise

[sergioten]

Hi! I recently bought a BMW F10 528i with the one and only bulletproof N52 engine. I know this is a 3 series thread, but there was a pretty big line up of 3 series with N52 engines. Today I've notices this weird low pitch noise coming from my engine. It kinda resembles a shot flywheel noise (my BMW is an automatic), but you can be the judge for yourself.

I found this video and the sound is exactly the same. Dropping the link below
https://www.youtube.com/shorts/hxTYEwsG5UU
Any suggestions are welcome, I'm hopeless here (probably the guy who uploaded this video is too)

[drewusmaximus]

Try removing the oil fill cap while the car is idling. Check to see if there's a slight vacuum, strong vacuum or no vacuum while removing the cap and let us know the result. Was the valve cover recently worked on? Pull off the first two spark plugs and see the condition of the plug. Is it dry? Is it wet? Is it oily? Is there caked on build up, i.e., carbon, old oil buildup? To me, it sounds like the diaphragm is failing, CCV system not doing its job. Report back with results.

[sergioten]

Try removing the oil fill cap while the car is idling. Check to see if there's a slight vacuum, strong vacuum or no vacuum while removing the cap and let us know the result. Was the valve cover recently worked on? Pull off the first two spark plugs and see the condition of the plug. Is it dry? Is it wet? Is it oily? Is there caked on build up, i.e., carbon, old oil buildup? To me, it sounds like the diaphragm is failing, CCV system not doing its job. Report back with results.

Oil cap is under a medium vacuum (doesn't matter if the engine is hot or cold), I can pull the cap off with low/medium amount of force.
The valve cover gasket was replaced a year ago by the dealership with Vanos bolts recall.
All the spark plugs are nice and dry, with small carbon deposits, but mainly they are as they supposed to be.

I noticed, that this sound appears after the engine is warmed up. I was listening into the engine bay, while the engine was cool, but didn't hear this specific sound. I haven't listened to the cold engine many times, so this might be a coincidence.

Is there a way to test the CCV system?


Thank you for replying!

[drewusmaximus]

A low/medium suction is good. It means the CCV is doing it's job. It shouldn't be effortless or hard to remove the oil fill cap. Are you able to plug in a scanner and look at the live data? Look at the short and long term fuel trims during idle. The percentage should be close to 0 and the acceptable max is +10 and -10. If you have a temperature reading gun, the one with the laser, you can check the PCV heater under the air intake to see if it's functional. Wait until the car cools. Check the temperature of the PCV heater while it's cold, then turn the ignition on, but not the car, run back to the engine bay and point the laser directly on the PCV heater again. You should see the temperature rise up over 100f. If it does, then the PCV heater is functional. When looking at the live data, check the temperature of the catalytic converters. At idle the catalytic converters should read around 800-900ish degrees. If the temp is higher, then there might be a blockage and cause back pressure to build in the engine.
Are you able to record the sound and upload it? It would be ideal to actually hear the sound from your car. When did you start noticing the noise? A few months ago? a few weeks ago? a few days ago? Are you able to scan the car for codes?

[Alphaexray]

So I had a good listen with headphones, I do hear the knock, it's more of a thump, but it is at rpm which eliminates rod/piston play. N52s had vibration damper issues with them coming loose and wobbling, so I'd check that first. Then there are the problems with the flange blots that fail, which lead to exhaust leaks (under passenger side ). The rear crankcase vent hose cracks which can be audible. Water pumps are notoriously bad, and if the bearings are going, they could run out of center and produce a sound (but it's usually high pitched). Then you get into the nasty problems, and I won't mention any of those until you've exhausted your search. Engine sounds quite nice.

[sergioten]

Today I tried to look into the live data using Carly, which didn't had any of catalytic converter data available, I guess its just a toy for reading the ECU trouble codes.. Tomorrow I will try to fire up ISTA/IMPA, hopefully it will give me some more live data options. I will try to record that exact sound as well. I will also check that crankcase vent hose and other things you guys mentioned!

Since I live in Europe and in Europe BMW exchanged the F10 N52 with N53, I've had my car shipped straight from USA. It had some front-end damage, but nothing serious- a front bumper with radiators were damaged. I've bought it around 2 months ago and it already came with this weird sound.

Yet, I already changed the spark plugs (with Bosch), oil filter cap (the filter holding part was broken from the cap), air filter and engine oil.


Thanks for replying! I was expecting to wait a year or two to get any replies on this thread, since most of these N52 posts were posted in 2015, but I'm glad we have this community!

[hakentt]

Hi! I recently bought a BMW F10 528i with the one and only bulletproof N52 engine

who told you that N52 is bulletproof engine? It is very weak engine, if there is any oil starvation the intake camshaft will wear out, intake cradle is part of the cylinder head, once it has little wear it will making knocking noises and there is no way of repairing that, new head has to be installed.

[g8r1fl]

A low/medium suction is good. It means the CCV is doing it's job. It shouldn't be effortless or hard to remove the oil fill cap. Are you able to plug in a scanner and look at the live data? Look at the short and long term fuel trims during idle. The percentage should be close to 0 and the acceptable max is +10 and -10. If you have a temperature reading gun, the one with the laser, you can check the PCV heater under the air intake to see if it's functional. Wait until the car cools. Check the temperature of the PCV heater while it's cold, then turn the ignition on, but not the car, run back to the engine bay and point the laser directly on the PCV heater again. You should see the temperature rise up over 100f. If it does, then the PCV heater is functional. When looking at the live data, check the temperature of the catalytic converters. At idle the catalytic converters should read around 800-900ish degrees. If the temp is higher, then there might be a blockage and cause back pressure to build in the engine.
Are you able to record the sound and upload it? It would be ideal to actually hear the sound from your car. When did you start noticing the noise? A few months ago? a few weeks ago? a few days ago? Are you able to scan the car for codes?

[mention]drewusmaximus [/mention] you’re always super helpful and knowledgeable! Thanks for that. I have a Foxwell NT530 reader and am learning how to use it. It has a lot of extra functionality like adaptations reset, etc and just today I found A/C relearn. Documentation is really lacking though. Is there somewhere I can find what acceptable ranges are for live data readings such as the fuel trim you mentioned? Last month I figured out how to read trans fluid temp for my drain and fill job.


Sent from my iPhone using Tapatalk

[drewusmaximus]

[mention]drewusmaximus [/mention] you’re always super helpful and knowledgeable! Thanks for that. I have a Foxwell NT530 reader and am learning how to use it. It has a lot of extra functionality like adaptations reset, etc and just today I found A/C relearn. Documentation is really lacking though. Is there somewhere I can find what acceptable ranges are for live data readings such as the fuel trim you mentioned? Last month I figured out how to read trans fluid temp for my drain and fill job.


Sent from my iPhone using Tapatalk

Attachment 727696 The fuel trims should show up in percentage. Depending on the scanner tool, the labeling for fuel trims can be:

SHRTFT1(%) Bank 1 - Cylinders 1-3
LONGFT1(%) Bank 1 - Cylinders 1-3
SHRTFT2(%) Bank 2 - Cylinders 4-6
LONGFT2(%) Bank 2 - Cylinders 4-6

STFT1(%)
LTFT1(%)
STFT2(%)
LTFT2(%)
Those are the labeling version I know of. The acceptable percentage range is up to +10% and -10% for both short term and long term for both banks. Anything above +10% and -10% is an issue.
If the percentage is above +10, the car is adding more fuel to the mix. If the percentage is over -10%, the car is reducing fuel output. Check your Foxwell and see where your fuel trims are at. I believe the Foxwell shows the trims by percentage.

[LindenV]

Noticing the exact same issue with my 2011 528i. You're the first post I've been able to find that's had the same problem- did you make any further progress?

[Brodles]

Try removing the oil fill cap while the car is idling. Check to see if there's a slight vacuum, strong vacuum or no vacuum while removing the cap and let us know the result. Was the valve cover recently worked on? Pull off the first two spark plugs and see the condition of the plug. Is it dry? Is it wet? Is it oily? Is there caked on build up, i.e., carbon, old oil buildup? To me, it sounds like the diaphragm is failing, CCV system not doing its job. Report back with results.

I am having the same issue as OP and this is the only thread I can find. I just replaced plugs/coils, which did not change the thumping sound, but in the process discovered the front four plug tubes had lots of oil in them. Plug electrodes were not wet, but had some caked on build up. I removed the oil cap while running, there was a reasonably strong vacuum, not hard to remove but a long audible hiss when removed. With it off, I did notice the thumping sound changed, much higher frequency but less audible. I also noticed the valvetronic motor seal appears to be leaking, a lot of residual oil around that area. Valve cover gasket looks like it has been replaced at least once, not much evidence of it leaking. Current plan is to replace the valvetronic motor seal and see if it changes anything. What is the diaphragm you mentioned that could be failing? Anything else you'd recommend trying?

[drewusmaximus]

I am having the same issue as OP and this is the only thread I can find. I just replaced plugs/coils, which did not change the thumping sound, but in the process discovered the front four plug tubes had lots of oil in them. Plug electrodes were not wet, but had some caked on build up. I removed the oil cap while running, there was a reasonably strong vacuum, not hard to remove but a long audible hiss when removed. With it off, I did notice the thumping sound changed, much higher frequency but less audible. I also noticed the valvetronic motor seal appears to be leaking, a lot of residual oil around that area. Valve cover gasket looks like it has been replaced at least once, not much evidence of it leaking. Current plan is to replace the valvetronic motor seal and see if it changes anything. What is the diaphragm you mentioned that could be failing? Anything else you'd recommend trying?

Depending on your year and model, the plastic valve covers have the built in CCV diaphragm. It sits at the rear left (passenger side) of the valve cover and it's round and has a thin hose connected to it that goes to the intake manifold. They do sell the diaphragm separately on Amazon, but you'll have to chip away the defective one on the valve cover and glue the new one on. If it were me, I'd replace the entire valve cover. Some models have the CCV under the intake manifold. They now make aluminum valve covers in replacement of the plastic. I heard decent reviews of it. The next time I have to change my valve cover, I will go metal. When opening the oil filler cap, the vacuum should be light, not hard to open. If the suction is moderate, it could be the CCV failing. I just listened to the video again. That thumping sound sounds like the camshafts. If you open the oil filler cap, the camshaft sound will be more prominent. I remember mine sounding like that before I replaced my valve cover. Once I replaced it, the sound went away, which makes me suspect it's the CCV system.

[Brodles]

Depending on your year and model, the plastic valve covers have the built in CCV diaphragm. It sits at the rear left (passenger side) of the valve cover and it's round and has a thin hose connected to it that goes to the intake manifold. They do sell the diaphragm separately on Amazon, but you'll have to chip away the defective one on the valve cover and glue the new one on. If it were me, I'd replace the entire valve cover. Some models have the CCV under the intake manifold. They now make aluminum valve covers in replacement of the plastic. I heard decent reviews of it. The next time I have to change my valve cover, I will go metal. When opening the oil filler cap, the vacuum should be light, not hard to open. If the suction is moderate, it could be the CCV failing. I just listened to the video again. That thumping sound sounds like the camshafts. If you open the oil filler cap, the camshaft sound will be more prominent. I remember mine sounding like that before I replaced my valve cover. Once I replaced it, the sound went away, which makes me suspect it's the CCV system.

Ah gotcha. Mine is a 2011 328i xdrive, has the plastic cover. I found out the dealer I bought it from performed the vanos bolt recall late last year, and it looks like they did a poor job resealing the valve cover as it's definitely leaking in a few spots, along with the spark plug tube seals. I'm guessing they re-used the same gaskets. I suppose the whole valve cover could be warped... I also thought the valvetronic motor seal was part of the vanos bolt recall procedure, at least according to fcp euro... and that's definitely leaking too. Sigh.

Sounds like I need to replace the valve cover/gaskets and report back. Appreciate the response!

[drewusmaximus]

Ah gotcha. Mine is a 2011 328i xdrive, has the plastic cover. I found out the dealer I bought it from performed the vanos bolt recall late last year, and it looks like they did a poor job resealing the valve cover as it's definitely leaking in a few spots, along with the spark plug tube seals. I'm guessing they re-used the same gaskets. I suppose the whole valve cover could be warped... I also thought the valvetronic motor seal was part of the vanos bolt recall procedure, at least according to fcp euro... and that's definitely leaking too. Sigh.

Sounds like I need to replace the valve cover/gaskets and report back. Appreciate the response!

I did the vanos bolts myself, but my CATs started failing and since I have the SULEV model, the car is still under SULEV warranty and the CATs were covered. While they were doing the CATs, I had the PCV heater and vanos bolts recall. I told them I did the PCV heater, but I didn't mention I did the vanos bolts, because why not let them double check my work. Sadly after a month my valvetronic gasket started leaking. I replaced it three times. I even used gasket sealer. I assume they didn't seat the valve cover correctly. Right now, it's not leaking, but I am planning to go with the aluminum valve cover. I've read good reviews.