Strange noise on start

[Ben1001]

After some ideas:

I have a 250 and I’ve noticed this noise twice now. Cold mornings on both occasions, it sounds like the noise is coming from behind the stereo - it’s more of an electrical noise, like a electric passing through a switch that’s stuck (if that makes sense). Lasts for 3-4 minutes. Turning the radio and blower off has no effect. Car seems to warm up and the noise is gone. Doesn’t sound healthy!

Any ideas folks?

 

[Texas]

3-4 minutes you say??

I have had a couple of times, since owning my 250 in Aug last year, a 2-3 second rattle from under the bonnet upon start up.

I am LED to believe that this is due the the engine oil draining out completely,  due to gravity!, of the upper hydraulic valve lifters and upon start up until oil pressure is produced the valves make a god awful noise, and from some homework I have done apparently it is acceptable! This does not look to be the same 'problem' as you are describing as if it went on for 2-3 minutes I would expect real damage.

paul m.

[chr15gb]

Try ejecting the cd's.  It could be chugging about even if Audio is off. 

Fan would've been my first choice but you turned it off,  can't think of anything else. 

[Texas]

Talking of CD's is your SatNav a CD based one or SD card as it might be the SatNav CD which is in behind the dash is it not?

paul m.

[Ben1001]

It’s an SD card, I have a Gen 3 IS.

It sounds like an electrical whirling noise, I don’t have a CD in the drive.

[rich1068]

I've had cars that you can hear the fans and (I assume) vents behind the dashboard adjusting for temperature and direction. A bit of a quiet whirr here and there. Could be that.

[dazed]

6 hours ago, Ben1001 said:

It’s an SD card, I have a Gen 3 IS.

It sounds like an electrical whirling noise, I don’t have a CD in the drive.

Probably worth posting on the gen 3 forum if you haven't already.

[is200 Newbie]

The Gen 2 has an electrical operated "flap" allowing air to enter the cabin through the filter housed in the glove box area.

Have you had a recent service where the filter was changed? The noise could be the motor straining to open or close the flap? The Gen 2 filter is located in the glove box area on passenger side

[Ben1001]

That’s a great point, thank you. I actually had the noise yesterday again and pulled in and turned the car off. The noise continued... would that happen with this flap?

Will speak to the dealer.

[is200 Newbie]

Possibly? If you have the fan on and the motors struggling with whatever mode the blower is in (re-circulate or circulate) and cannot open or close the flap but I would expect this to be the case after the filter was replaced as the flap is quite delicate and wont last that long if struggling to operate.

A twig or something in the fan blower? Have you tried operating the fan at different settings to eliminate this?

Does the sound go up/down with the engine or is it more constant? At what point during the drive does it happen?

I also believe, on the gen 2's at leat, that there is a small fan on the radio

Do you have a video of the sound?