Help Diagnosing Possible VANOS issue (noise at ~2500 rpm on decel)

Hey all,

Video Example posted to youtube. If you listen on decel you can hear the quick chatter sound (its coming from the engine bay).

I have done extensive maintenance to my E90 m3: RB, TA, replaced the plastic vanos caps with metal ones (bolt-on), check timing, new plugs, valve covers, fluids, etc. I then had some bodywork done so I assume the car sat for a while. When I got it back everything seemed fine, but then I started hearing this brief chattering noise when engine is dropping in RPMs. The noise happens around 2500 RPM and lasts for a split second. Load or no-load, but only when the engine is dropping in RPM from ~3k.

Here are two of the threads I checked through:
https://www.m3post.com/forums/showthread.php?t=1742823
https://www.m3post.com/forums/showthread.php?t=603650&page=3

One post says: "I believe the consensus is the rattle is from the actual adjusters at the end of the cam shafts. I can surmise thet a possible leaky check valve could have caused the rattle downstream but once its internal to the adjuster it needs to be replaced."

Another said he had to replace the timing chain tensioners. Someone else said it was low pressure fuel pump related? Someone else said its due to bad or low octane fuel. Someone else said conrad bearings.

Another says he had to completely rebuild the vanos due to a shearing vanos gear pin here. But it seems like that was an e46 issue.
I found this document with vanos info on page 14: https://ia801005.us.archive.org/11/items/BMWTechnicalTrainingDocuments/ST709%204th%20Generation%20M3%20Complete%20Vehicle/03_S65B40%2520Engine.pdf?
I don't understand how these pins could shear. I have not tried driving in 6th gear and listening for this rattle yet though.

I also asked my shop about replacing the vanos check valves and he said he's never heard of that (shop owner had a supercharged e92 m3 for quite some time). I already had them in there replace the vanos caps and check timing. I asked them about this noise and they didn't think it was anything to worry about. Could they have missed this while they were doing the valve cover work? Or is my timing off or timing chain damaged?

I did notice my xpipe might have a slight leak on one side as well (initial water dripping on startup).

My guess is I need to diagnose my vanos check valves first and go from there. I am going to try to hook up ista+ in a minute. But I am losing my mind over this noise. Any help appreciated.

edit: when I had vanos caps replaced I did have them use new bolts. Do the VANOS oil pump gears themselves wear down over time? I also think I have the original o2 sensors still.

Bump

I doubt you could hear anything if it was a check valve or vanos adjuster. Sounds more like a belt to me. Remove all the belts and see if the sound goes away.

Redd wrote

I doubt you could hear anything if it was a check valve or vanos adjuster. Sounds more like a belt to me. Remove all the belts and see if the sound goes away.

Quick question. So the car would start without all belts but just wouldnt recharge battery or have p/s or whatever right?

It does look like one pulley is "wobbly"

Appreciate it.

fengrr wrote

Quick question. So the car would start without all belts, but just wouldn't recharge battery or have p/s or whatever right? It does look like one pulley is "wobbly". Appreciate it.

Correct, car will start and run off the battery voltage. No power steering, alternator, A/C compressor, or water pump drive without the belts so don't run it for long without the belts. A better video with the camera closer to the noise source could help with diagnosis. The flutter/rattle I hear sounds like slack in the timing chain(s). So I speculate you 'might' have a bad timing chain tensioner(s). How old are the chain tensioners? Are you running the correct 10W60 viscosity oil? Worn out serpentine belt tensioners and pulleys can also make some weird noises. Search YouTube for examples or the forum noise thread.

DrFerry wrote

The flutter/rattle I hear sounds like slack in the timing chain(s). So I speculate you 'might' have a bad timing chain tensioner(s). How old are the chain tensioners? Are you running the correct 10W60 viscosity oil? Worn out serpentine belt tensioners and pulleys can also make some weird noises. Search YouTube for examples or the forum noise thread.

Aw timing chain tensioner going bad can cause a "clatter" according to FCPEuro part description.

The car is about due for an oil change but I am using liqui-moly 10w60 with ceratec additive.

I believe original timing chain at ~114k miles. Is this due at 120k?

Should I try running liqui-moly engine flush and swapping in new oil?

fengrr wrote

Aw timing chain tensioner going bad can cause a "clatter" according to FCPEuro part description. The car is about due for an oil change but I am using liqui-moly 10w60 with ceratec additive. I believe original timing chain at ~114k miles. Is this due at 120k? Should I try running liqui-moly engine flush and swapping in new oil?

It's not the timing chain but the hydraulic timing chain tensioners that could be bad. IF the chain tensioners are OEM and have 114K miles then they don't owe you anything and are past due for preventative replacement. No need to prematurely change the oil UNLESS it's due for an oil and filter change. Search the forums for DIY threads about the tensioners. Consider posting another better video of the sound. PS: See #8 in the www.realoem.com parts image below.

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DrFerry wrote

It's not the timing chain but the hydraulic timing chain tensioners that could be bad. IF the chain tensioners are OEM and have 114K miles then they don't owe you anything and are past due for preventative replacement.

Thanks, yes I know you meant the tensioners. What is the recommended interval for replacing those? I was also wondering if timing chain and guides have a service life? I was told 120k by a shop but I didn't know about the tensioner interval being less.

Thanks again.

fengrr wrote

Thanks, yes I know you meant the tensioners. What is the recommended interval for replacing those? I was also wondering if timing chain and guides have a service life? I was told 120k by a shop but I didn't know about the tensioner interval being less. Thanks again.

I don't think there is a recommended service replacement interval for the timing chain tensioners i.e. replace them when they go bad or preventaively. As far as I know; it's the same guideline for the chains and guides i.e. just like with wheel bearings -> when they go bad it's time to replace... Remember the Advanced Search function is your friend on this forum.

DrFerry wrote

I don't think there is a recommended service replacement interval for the timing chain tensioners i.e. replace them when they go bad or preventaively. As far as I know; it's the same guideline for the chains and guides i.e. just like with wheel bearings -> when they go bad it's time to replace... Remember the Advanced Search function is your friend on this forum.

I read another thread (from Redd) and they said that oil could potentially drain from the tensioner if the car sat for a while (my car sat for a while at body shop). So would I definitely need to replace the tensioner?

I found a guide to replace the tensioner and apparently you can replace them without pulling the valve covers, is it ok to perform this procedure this way? You think I should try swapping them from side-to-side and see if noise changes?

My plan would be to change oil & change tensioners and see if it goes away. Maybe I should check oil pressure. But I am also worried there is a potential bad valve lifter (Redd's case).

fengrr wrote

I read another thread (from Redd) and they said that oil could potentially drain from the tensioner if the car sat for a while (my car sat for a while at body shop). So would I definitely need to replace the tensioner? I found a guide to replace the tensioner and apparently you can replace them without pulling the valve covers, is it ok to perform this procedure this way? You think I should try swapping them from side-to-side and see if noise changes? My plan would be to change oil & change tensioners and see if it goes away. Maybe I should check oil pressure. But I am also worried there is a potential bad valve lifter (Redd's case).

Yes, I agree with your plan mentioned above: i.e. to replace both tensioners and see if the noise goes away, but only after running the car with no belts to be certain it's not a bad belt pulley etc.