noise coming from boot when closing door

[unity]

I have noticed a banging noise coming from the boot when closing any of my car doors. Please see the video below, and although the quality is not good you can clearly hear the sound.

For the purpose of the video I was holding the exterior door handle open so the door would no latch shut, and very lightly I open and close the door so you can hear the noise. It's definitely not any of the panels because I tried pushing around the door frame (with door open and closed) and I don't get that sound.

http://s635.photobucket.com/albums/u...t=MOV00203.flv

[unity]

Well I just found this same thing also happens on my other car too. It just seems strange than I never noticed this before since I have now had both these cars for over 1 year.

Anyway, I'm still interested why the car makes this noise.

[dinorider]

The most likely source is the cabin air vent.

All cars have it, and the purpose is to let stale air out of the car when your a/c is set to take air in, and also to vent air out of the car when you close the door. If the air doesn't vent out, your ears will feel a pop when you close the door and you're in the car as the cabin air compresses.

The vent is always at the rear of the car, and usually (though not always) visible in the boot. Sometimes in covered by the boot lining/trim. Externally, it's usually hidden, and most likely covered by the rear bumper.

if you take off the rear bumper you'll probably see a square hole leading into the car somewhere, and it'll likely be covered by a top-hinged piece of rubber/plastic that opens only one way (outwards). This way, when air is forced through the vent from inside the car the flap opens to let air out, but air/rain blowing in from outside can't get in. Well in theory at least.

The noise you're hearing is likely to be the vent's door/flap opening and then closing back down. Well as you close your car door it pushes a wave of air into the car, which exits via the this vent.

Or you might have CD changer cables or something routing past the vent in the boot, and the airflow as it rushes out causes the cables to move, making noise.


How do I know? My DC2 (and others before it) makes the same noise. And I've taken off the DC2's rear bumper to clean the vent from the outside. There's an unbelievable amount of dust around it.

The vent door/flap is very sensitive to air pressures. A car driving past mine when I'm stopped at the lights waiting to turn right can cause a strong enough vacuum to suck the vent door open, creating that momentary 'flap-flap' noise that sounds like something's loose in the boot.

[unity]

The most likely source is the cabin air vent.

All cars have it, and the purpose is to let stale air out of the car when your a/c is set to take air in, and also to vent air out of the car when you close the door. If the air doesn't vent out, your ears will feel a pop when you close the door and you're in the car as the cabin air compresses.

The vent is always at the rear of the car, and usually (though not always) visible in the boot. Sometimes in covered by the boot lining/trim. Externally, it's usually hidden, and most likely covered by the rear bumper.

if you take off the rear bumper you'll probably see a square hole leading into the car somewhere, and it'll likely be covered by a top-hinged piece of rubber/plastic that opens only one way (outwards). This way, when air is forced through the vent from inside the car the flap opens to let air out, but air/rain blowing in from outside can't get in. Well in theory at least.

The noise you're hearing is likely to be the vent's door/flap opening and then closing back down. Well as you close your car door it pushes a wave of air into the car, which exits via the this vent.

Or you might have CD changer cables or something routing past the vent in the boot, and the airflow as it rushes out causes the cables to move, making noise.


How do I know? My DC2 (and others before it) makes the same noise. And I've taken off the DC2's rear bumper to clean the vent from the outside. There's an unbelievable amount of dust around it.

The vent door/flap is very sensitive to air pressures. A car driving past mine when I'm stopped at the lights waiting to turn right can cause a strong enough vacuum to suck the vent door open, creating that momentary 'flap-flap' noise that sounds like something's loose in the boot.

Thanks so much for the explanation. It definitely sounds like something is opening/closing with a loud click. When I turn off my Euro I get three click sounds from the engine bay. This is making a similar click sound only much louder.