[Minty]

My 340i is coming up to 3 years old and I don’t remember it ever making this noise on cold start. After starting and the revs dropping I can hear what I can only describe as a loud clacking noise. After another 20-30 seconds it disappears and I can then hear the normal DI injector tapping noises.

Any suggestions?

[dizzy619]

Take it to the dealer...

[creepy coupe]

Hydraulic tappet leaking down?

[RoShambolt]

Originally Posted by creepy coupe

Hydraulic tappet leaking down?

Loose exhaust mode valve flapper? I think it has been discussed in here on another thread. Mine has done it twice, I think it may be that because it's sounds similar to mine when it did it, also I believe the valves are both open on cold start, so when it goes to low idle (in comfort) the valve closes, hence the change after it has been running for a bit.

[creepy coupe]

Originally Posted by RoShambolt

Loose exhaust mode valve flapper? I think it has been discussed in here on another thread. Mine has done it twice, I think it may be that because it's sounds similar to mine when it did it, also I believe the valves are both open on cold start, so when it goes to low idle (in comfort) the valve closes, hence the change after it has been running for a bit.

Could be. Although the exhaust valve should be closed on cold start. mine last about 25 -30 secs before it opens.

[RoShambolt]

Sounds similar

https://www.bimmerpost.com/forums/sh...php?p=22945355

[RoShambolt]

Originally Posted by creepy coupe

Could be. Although the exhaust valve should be closed on cold start. mine last about 25 -30 secs before it opens.

I thought it was the other way around, cars always start in comfort. Which is one exhaust pipe open in usual operation. But the turn over louder on starts until they go low idle, and that was because both valves being open. Something to do with reduced emissions on starts? I could be way off here, I've read a hell of a lot of stuff on this forum so may well be wrong.

[creepy coupe]

Originally Posted by RoShambolt

Sounds similar

https://www.bimmerpost.com/forums/sh...php?p=22945355

I think Minty's sound heavier.

[RoShambolt]

Originally Posted by creepy coupe

Could be. Although the exhaust valve should be closed on cold start. mine last about 25 -30 secs before it opens.

You are indeed correct. After a little digging.

I copied the below posts and text from the thread I just found.

Originally Posted by crono06

Does setting the car in Sport mode open up the flap as well? I swear whenever I put it to Sport, the exhaust is more audible. Just as reference, I have Sport mode set to chassis only (regular/Comfort setting throttle/drivetrain).

When I asked BMW for specifics of when the exhaust will be open, they said during cold starts, the left exhaust pipe will be closed for approximately 1 - 2 minutes. I was told they designed this for both noise-control reasons and vehicle warm-up. You will then here it open up and it will remain open.

However, while driving in Comfort or Eco Pro, it will adapt to driving habits. If you are not accelerating harshly, it will keep it closed most of the time to give off less sound. If you floor it though, it will open up. It will continue to open in close based on how much you are trying to accelerate.

When in Sport/Sport+ mode, the exhaust flap will remain completely open and the exhaust will start having more noise (the gurgling sound) whenever the engine RPM is decreasing. To hear what I'm talking about, roll down your windows and manually downshift to kick up your engine RPM to around 2500 - 3000 RPM and let the engine speed decrease. I usually hear it gurgle most if the RPM decreases near that range that.

Sport will also make the shifting 'grunt' noise more often in Sport mode. When accelerating hard, with the throttle past half way, manually shift around 4500 RPM and you will hear the noise I'm talking about. They didn't specify this but I believe the shifting noise is only with the Sport Auto.

Hope this helps..

[creepy coupe]

Originally Posted by RoShambolt

I thought it was the other way around, cars always start in comfort. Which is one exhaust pipe open in usual operation. But the turn over louder on starts until they go low idle, and that was because both valves being open. Something to do with reduced emissions on starts? I could be way off here, I've read a hell of a lot of stuff on this forum so may well be wrong.

You're right. it has been discussed a lot. I think the general consensus was to heat the cat up faster.And yes reduce the emissions.

[creepy coupe]

Originally Posted by RoShambolt

You are indeed correct. After a little digging.

I copied the below posts and text from the thread I just found.



When I asked BMW for specifics of when the exhaust will be open, they said during cold starts, the left exhaust pipe will be closed for approximately 1 - 2 minutes. I was told they designed this for both noise-control reasons and vehicle warm-up. You will then here it open up and it will remain open.

However, while driving in Comfort or Eco Pro, it will adapt to driving habits. If you are not accelerating harshly, it will keep it closed most of the time to give off less sound. If you floor it though, it will open up. It will continue to open in close based on how much you are trying to accelerate.

When in Sport/Sport+ mode, the exhaust flap will remain completely open and the exhaust will start having more noise (the gurgling sound) whenever the engine RPM is decreasing. To hear what I'm talking about, roll down your windows and manually downshift to kick up your engine RPM to around 2500 - 3000 RPM and let the engine speed decrease. I usually hear it gurgle most if the RPM decreases near that range that.

Sport will also make the shifting 'grunt' noise more often in Sport mode. When accelerating hard, with the throttle past half way, manually shift around 4500 RPM and you will hear the noise I'm talking about. They didn't specify this but I believe the shifting noise is only with the Sport Auto.

Hope this helps..

You might find this of interest

https://www.youtube.com/watch?v=_BB8MRGpjIo&t=45s

[Minty]

Thanks for the replies. I am pretty certain it is not exhaust noise...it is definitely coming from the engine area.

[Sasquartch]

It's always difficult to tell from a sound clip from a phone, however it sounds like a noisy belt tensioner to me

But really you need to take it to a dealer for a proper listen as it could be any number of things

[Minty]

Picked my car up from dealer yesterday who replaced all 6 injectors - problem solved . Top marks to dealership (BMW High Wycombe) for taking it seriously and resolving under warranty.

It is still noisy on startup (as are all B58's) but it doesn't make that tapping / clacking noise now.

Master technician updated the software (not sure what modules) but all my custom settings gone. Gear change seems smoother, and cold start definitely different but other than that all good so far.

[cfm56d7b]

Originally Posted by Minty

Picked my car up from dealer yesterday who replaced all 6 injectors - problem solved . Top marks to dealership (BMW High Wycombe) for taking it seriously and resolving under warranty.

It is still noisy on startup (as are all B58's) but it doesn't make that tapping / clacking noise now.

Master technician updated the software (not sure what modules) but all my custom settings gone. Gear change seems smoother, and cold start definitely different but other than that all good so far.

Thanks for sharing the update. It's interesting that all 6 injectors were replaced. Perhaps the labor to isolate the injector in question would be more expensive than replacing all of them.

[Pequin]

Originally Posted by Minty

Picked my car up from dealer yesterday who replaced all 6 injectors - problem solved . Top marks to dealership (BMW High Wycombe) for taking it seriously and resolving under warranty.

It is still noisy on startup (as are all B58's) but it doesn't make that tapping / clacking noise now.

Master technician updated the software (not sure what modules) but all my custom settings gone. Gear change seems smoother, and cold start definitely different but other than that all good so far.

BMW High Wycombe are my favourite dealership, shame Dick Lovett are closer to me by 110 miles.

[Minty]

Originally Posted by cfm56d7b

Thanks for sharing the update. It's interesting that all 6 injectors were replaced. Perhaps the labor to isolate the injector in question would be more expensive than replacing all of them.

Spot on, they believed it was one noisy injector but it was safer to replace all 6.

Since the software update it definitely runs ‘differently’...haven’t driven it much so will reserve my judgement.

[cfm56d7b]

Originally Posted by Minty

Spot on, they believed it was one noisy injector but it was safer to replace all 6.

Since the software update it definitely runs ‘differently’...haven’t driven it much so will reserve my judgement.

It was actually a very prudent decision. Why have one injector perform as new and leave other injectors in potentially less than optimal state?

Your dealer was 100% correct.

[ryanpat198808]

Any chance that video showing the sound can be uploaded again as I'm getting a weird noise on startup that doesn't seem to happen all the time. It's like a high pitched whirring sound.

[Minty]

Originally Posted by ryanpat198808

Any chance that video showing the sound can be uploaded again as I'm getting a weird noise on startup that doesn't seem to happen all the time. It's like a high pitched whirring sound.

Hi,
Unfortunately not as I don't own the car any more so deleted the videos. My noise was more a rhythmic clack, clack noise in time with the engine.

I do remember quite a few whirring noises, in fact my X3 M40i makes similar noises.
Minty