Metal Knocking Sound when ignition and engine is switched off

Hi Folks,

Here is a recorded video for an abnormal metal knocking sound when the ignition and engine is switched off: https://youtube.com/shorts/MRiBoI4Z3xw?feature=share. This is a 2017 mazda 6.
This is how the knocking sound is produced:
1. drive back from a normal trip, drive forward into garage
2. shift to neutral, turn on electric parking brake, shift to parking
3. turn the ignition off. Exactly at the time when ignition and engine is switched off, the sound is heard.

I am not sure if anyone experienced this. I took the car to dealer and they diagnosed it to be the parking brake actuator, the sound comes from the rear. However, I kind of doubt the diagnosis result, because:
1. I think I heard the sound from the front, not from the rear.
2. I don't understand why there is not such sound when I turn on/off the parking brake. How would turning ignition off cause that sound from the parking brake actuator?

Thanks, Guys!
 
to be honest I can't really hear anything similar with a metal knocking. Yes, there is a sound in there and it seems that its related to engaging the parking brake. Which btw, why are you engaging parking brake in a garage ?

I wouldn't touch the parking brake unless I am on a steep incline.
 
Hi @Muggs1,
Thanks for the reply. The dealer did a diagnosis and gave a conclusion: the sound is coming from the EPB actuator engaged. When ignition is switched off, the actuator still engage a bit more even I already turn on the EPB before switch ignition off. I was not fully convinced. However yesterday I just got back my car without replacing the actuator. I tried a few times: I didn't turn on EPB before ignition off. And I don't hear the knocking sound anymore. So maybe the dealer diagnosis was right. I am going to do a few more tests: turn on EPB and off ignition, and see if I still hear the sound.

Regarding turning on EPB in garage, my purpose is not let the vehicle have any movement after shutdown, and to protect the transmission, as well. Also the mazda user manual recommends that https://www.mazdausa.com/static/manuals/2020/cx-30/contents/05050107.html : "Apply the parking brake when leaving the vehicle:

Not applying the parking brake when parking the vehicle is dangerous as the vehicle may move unexpectedly and result in an accident."
 
Just to add, I also apply the parking brake whenever I put the car into park. It's called a "parking brake" after all. If the car is parked on an incline, it saves the transmission from slamming into gear, which my wife happens to do all the time, regardless of whether the ground is level or not.
 
To add the conclusion after a few more tests: the sound is indeed from the rear. It is related to the EPB, like the dealer said. If I don't turn on the EPB, there is no sound when ignition off. If I do turn on, the sound still exists.

Wow, this EPB actuator is so unreliable. The car is just 4.5 years old and 50k miles. Kind of disappointed with this. I should file a complaint to mazda usa :confused:
 
By all means, file that complaint. At the very least just to make them aware of the issue. However, I don't know if I would call the EPB actuator in all Mazda6s unreliable. The issue doesn't seem very widespread, seems more like a one-off incident. Has this issue seen a lot of reports elsewhere (FB groups, other forums)?
 
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