Cold start rattle 2-3 seconds then gone.

[ac427]

The factory CSL tune would do this 2-3 sec cold start rattle noise. The revs would pop up to near 2k before they immediately dropped back down to cold start idle. With the cold start map adjusted, it no longer does this rattle. Disabling cold start might be a good, easy test.

I wonder if they changed that on the later CSL tune. I have the CSL tune on mine and i'm pretty sure it doesn't raise initial revs to 2krpm.

[Slideways]

The factory CSL tune would do this 2-3 sec cold start rattle noise. The revs would pop up to near 2k before they immediately dropped back down to cold start idle. With the cold start map adjusted, it no longer does this rattle. Disabling cold start might be a good, easy test.

[Andratch]

IMO If your behaves or sounds and differently after an oil change that is a very somber indicator that your oil change intervals are way too long.

My oil is only about 200 miles / 3 months old, though there was a HPDE in there. It’s LiquiMoly synthetic 10W60

[lemoose]

IMO If your behaves or sounds and differently after an oil change that is a very somber indicator that your oil change intervals are way too long.

[Andratch]

Cool,

i found this a issue for me, with another car i owned in the past. Once the oil got a bit old, ( length of time ) ie, more than 6 months, I would get the rattle start, This was a car that sat 5 days a week, so the mileage on the oil was low. Once i changed the oil, the rattle would disappear again. I figured it was just the quality of oil at the time, now reading this post has me thinking otherwise

Interesting. I will say, my oil is only about 3 months old and only has a few hundred miles on it - but a few of those miles includes a HPDE event. I still wouldn't say that's my problem here, but if all else fails an oil change is cheaper than taking off the timing chain cover.

I did replace my timing chain tensioner with a new one back over the winter because I didn't yet understand that the S54 is just a noisy engine in general, and so I was trying to eliminate a 'normal' noise by swapping what I now believe was a good, working tensioner with another new one. The shop called me on Friday to say that they took out the one I bought from FCP and replaced it again, and didn't hear the sound after 24 hours of sitting.....so, fingers crossed all this fuss was a faulty replacement part. I'm not overly confident, but I can't really see what else it could be.

[ac427]

I just saw this title, and thought i would share

https://youtu.be/lqjVGhzDz2U

[BL92]

I just saw this title, and thought i would share

[BL92]

Cool,

i found this a issue for me, with another car i owned in the past. Once the oil got a bit old, ( length of time ) ie, more than 6 months, I would get the rattle start, This was a car that sat 5 days a week, so the mileage on the oil was low. Once i changed the oil, the rattle would disappear again. I figured it was just the quality of oil at the time, now reading this post has me thinking otherwise

[Andratch]

Any updates to this thread ? It's probably the brand of oil ?

No updates yet, car is still at the shop. It's a pain to diagnose because they only get 2 seconds with the sound before it has to be left for 6 hours to kill off the oil pressure.

I would say it's definitely NOT the brand of oil. It has Mobil 1 in it now, OEM weight.

[BL92]

Any updates to this thread ? It's probably the brand of oil ?

[sapote]

I did this as well. Didn't notice it at first and thought i'd have to grind the new housing, but then noticed i could gently persuade the 'nut' to proper clearance with a hammer.

FYI, the shop had three techs with ears on the car this week to identify where the sound is coming from, and they feel it's coming from "the tensioner level within the engine" - basically, not up top with vanos, and not bottom with bearings. They know my tensioner is new, and I gave them the spare that I purchased from FCP. I'm not sure where the next steps will be - my timing chain feels pretty taught from what I can tell by poking through the tensioner hole, perhaps there's a guide with a broken piece that the chain rattles against until it's fully taught? I don't really know.

My only other thought would be - maybe oil pump tensioner? That's on a separate chain...that tensioner isn't hydraulic though so I'm not sure why it would cause a problem.

with the alt ear supported on something it's safe to tap the nut rearward with a hammer. But I wouldn't use a hammer on the long bolt with the alt mounted on the car as this could break the alt ear, then it's a bigger headache.

Have the top right side chain guide ever replaced? At 70K miles and above this piece can break off the tip.

[Andratch]

Alt is mounted by 2 long bolts: the top one serves as a pivot and doesn't lock the alt down (also holds the idler) and the bottom one locked the alt down by pulling the special sliding nut forward to clamp around the OFH flange.
I use a bolt and 22mm socket as spacer to pull the sliding nut rearward to "open the clamp" for remove/install. So I'm not surprised that the factory didn't set the nut at max "opened clamp" position.

To make it easy to remove the alt off the car, we should pull the said nut rearward about one turn of threads and this save our backache from working hard trying to pull it out.

The pic is a unit from non-M E46 but the feature is the same for M3 alt.

I did this as well. Didn't notice it at first and thought i'd have to grind the new housing, but then noticed i could gently persuade the 'nut' to proper clearance with a hammer.

FYI, the shop had three techs with ears on the car this week to identify where the sound is coming from, and they feel it's coming from "the tensioner level within the engine" - basically, not up top with vanos, and not bottom with bearings. They know my tensioner is new, and I gave them the spare that I purchased from FCP. I'm not sure where the next steps will be - my timing chain feels pretty taught from what I can tell by poking through the tensioner hole, perhaps there's a guide with a broken piece that the chain rattles against until it's fully taught? I don't really know.

My only other thought would be - maybe oil pump tensioner? That's on a separate chain...that tensioner isn't hydraulic though so I'm not sure why it would cause a problem.

[bavarian3]

Alt is mounted by 2 long bolts: the top one serves as a pivot and doesn't lock the alt down (also holds the idler) and the bottom one locked the alt down by pulling the special sliding nut forward to clamp around the OFH flange.
I use a bolt and 22mm socket as spacer to pull the sliding nut rearward to "open the clamp" for remove/install. So I'm not surprised that the factory didn't set the nut at max "opened clamp" position.

To make it easy to remove the alt off the car, we should pull the said nut rearward about one turn of threads and this save our backache from working hard trying to pull it out.

The pic is a unit from non-M E46 but the feature is the same for M3 alt.

Amazing info. Live and learn! I had no idea. This certainly would've gave me that half mm or so I needed to slide it on easier.

[sapote]

Hm no I did not. was not aware of this. I do wonder if the Bosch(non-genuine) might be different.

Alt is mounted by 2 long bolts: the top one serves as a pivot and doesn't lock the alt down (also holds the idler) and the bottom one locked the alt down by pulling the special sliding nut forward to clamp around the OFH flange.
I use a bolt and 22mm socket as spacer to pull the sliding nut rearward to "open the clamp" for remove/install. So I'm not surprised that the factory didn't set the nut at max "opened clamp" position.

To make it easy to remove the alt off the car, we should pull the said nut rearward about one turn of threads and this save our backache from working hard trying to pull it out.

The pic is a unit from non-M E46 but the feature is the same for M3 alt.

[bavarian3]

Did you pull the special round nut at the rear of the alt out (rearward) couple mm before trying to install it on the OFH? I pulled it rearward before trying to remove the alt from car every time.

Hm no I did not. was not aware of this. I do wonder if the Bosch(non-genuine) might be different.