StephenW2016

Our 2017 C300 coupe sometimes will make a siren sound after parked in the garage for 30~40 minutes, it'll stop after a minutes or so. There're no other devises in the garage or anything nearby would make such sound.

Happened (or got caught) 4 times already, went to the dealer, hooked up to computer and no fault code.

Finally caught it on video twice in the garage, I don't know if you can hear it clearly but this is what it sounded like:

Anyone ever heard of such a sound? TIA.

ItalianJoe1

Does your car have the LED headlights?

StephenW2016

Thank you for your reply.

I'm not sure what kind of headlight it has, my wife lost the original window sticker.

Do you think the LED headlight has something to do with it?

StephenW2016

I'm not sure, my wife lost the window sticker.

Do you think it has something to do with the sound?

Thank you.

ItalianJoe1

Yes, the LED lights have fans in them that can run up to an hour after to control temperatures. There have been instances of it being reported like this, so it may very well be normal.

StephenW2016

Thank you so much for your help, I just found out this coupe has LED headlight.

I'll go check with my service adviser if he knew anything about it.

Best regards.

StephenW2016

Will the fan start to work 30 minutes after engine off? Because all 4 times we caught it were about 30~40 minutes after car parked. And all happened in daytime. Thank you very much.

StephenW2016

And this is what it sounded:

ItalianJoe1

It may be another pump running, it's hard to say. There are several. Even auxiliary coolant pumps to keep the turbos at a controlled temperature as the car cools down. Anything can run at weird times after shutdown if the conditions are right.