F31 noise on acceleration - tell me it’s nothing!

[FieldAtlanta]

Everyone’s favourite internet game… diagnose that audible sound with only a poor written description to go on!

I’m getting used to my - new to me - F31. It’s a 320i, xDrive, auto model from late 2016 (thread here: https://www.pistonheads.com/gassing/topic.asp?h=0&... and have noticed a slight noise that I wanted to get opinions on.

The noise is very subtle. Sounds like it could be electric and is specifically only audible when lightly touching the accelerator. The second you stop, it stops. It sounds similar to a very quiet hair dryer (no “should have got a six cylinder” jokes, please) and could easily be mistaken for roof rails whistling.

Anything to worry about or investigate a little further or is there something that would explain this?

[sortedcossie]

My brother had the heater blower replaced under warranty for a noise that sounds along the lines of that. They initially replaced both turbos (320d) then when it didn't cure it the heater was next on the list.

[bmwmike]

Could it be the zf8 whistle or siren noise?

[d_a_n1979]

bmwmike said:

Could it be the zf8 whistle or siren noise?

Was about to say could it be the ZF8 whistle...

Grant at Automatic Transmissions, Preston said a full fluid & filter service usually sorts that; though it's nothing to be concerned about either...

[bmwmike]

d_a_n1979 said:

bmwmike said:

Could it be the zf8 whistle or siren noise?

Was about to say could it be the ZF8 whistle...

Grant at Automatic Transmissions, Preston said a full fluid & filter service usually sorts that; though it's nothing to be concerned about either...

Mine only used to do it in DS mode, and when i was "on it" a little. Honestly sounded like a police siren. Almost like an acceleration limiter . Mine went away on its own.

Edited by bmwmike on Tuesday 21st November 09:54

[sortedcossie]

JRHartless said:

I would have thought replacing the heater blower would be ahead of replacing two turbos in terms of cost?!

Although any garage that can't tell whether a noise is coming from the heater blower or the turbos probably deserves to shoot themselves in the foot with incuring misdiagnosis costs.

BMW main dealer, car was only 2 years old. I think the parts required needed a dash out job, so possibly worse than swapping turbos.

[Hammy98]

Does it go away with the AC/Blowers turned off?

My M4 did this but it never got any worse, and it was really quiet so didn't bother me.

I was told it was the idler pulley.