Cold start rattle 2-3 seconds then gone.

[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.

[sapote]

my alternator(bosch) didn't want to fit on the new housing so I had to do go through some anger and filing/sanding.

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.

Edited: not round nut but it can slide inside that hex shape hole.

[bavarian3]

Typo on my part. Instructional videos showed removing the fan for the OFH. I didn't find it necessary, and didn't think removing it would have made anything any easier.

Isn't it easier to remove the belt, tensioner and idler with the clutch fan removed?

How do you remove the belt off the tensioner/idler with the fan installed?

Just completed the OFH replacement this weekend. Can confirm, no need to remove the clutch fan. I don't like removing it if I don't have to because it risks bumping the radiator, and I generally find re-installing it along with the shroud to be mildly cumbersome. Belt drive and alternator assembly is no problem with the right extensions.

The real PITA is that drive side air duct portion of the fan shroud that the upper radiator hose feeds through. One day I'm going to lose it and set the thing on fire. Also, my alternator(bosch) didn't want to fit on the new housing so I had to do go through some anger and filing/sanding.

Install process aside, my lagging oil light on cold startup seems to be solved. So I guess per the points in this thread this remedy was correct. Sorry this doesn't help your case, Andratch

[sapote]

Typo on my part. Instructional videos showed removing the fan for the OFH. I didn't find it necessary, and didn't think removing it would have made anything any easier.

Isn't it easier to remove the belt, tensioner and idler with the clutch fan removed?

How do you remove the belt off the tensioner/idler with the fan installed?

[Andratch]

Agree that no need to remove fan for changing oil filter, but removing the fan makes it easy to unbolt the OFH.

Typo on my part. Instructional videos showed removing the fan for the OFH. I didn't find it necessary, and didn't think removing it would have made anything any easier.

[sapote]

In a lot of the instructional videos for replacing the oil filter, they took off the fan and fan clutch (as an assembly) to get more space, but I found it to be an unnecessary step.

Agree that no need to remove fan for changing oil filter, but removing the fan makes it easy to unbolt the OFH.