Weird noise

[Linus27]

Been hearing this weird noise coming from what sounds like the back of my DC5. Noticed it today so decided to have a proper listen. The noise can only be described as a flutter or ticking type sound, similar to when a bird flutters its wings very quickly. It seems to come from the rear and at first it sounded like the rear near side but it actually moved across from one side to the other a few times. I worked out I could make the noise by going up to over 4K revs in 4th for example and then lifting off the throttle. As the revs dropped, this flutter noise would happen for a few seconds and then disappear.

Any ideas? I'm wondering if exhaust related but It's more rear near side. Perhaps some kind of vibration.

 

[Honda-atr]

Aren't those the air outlets, there are flaps on there which make a ticking sound.
Did you remove the carpet/lining in the trunk? When I removed everything in the trunk I noticed the sound. After a while I found out that this was caused by the flaps on the outlet which were ticking.

I hope this make some sense

 

[Honda-atr]

You can see a part of it in this picture behind the opening.

 

[Linus27]

Aren't those the air outlets, there are flaps on there which make a ticking sound.
Did you remove the carpet/lining in the trunk? When I removed everything in the trunk I noticed the sound. After a while I found out that this was caused by the flaps on the outlet which were ticking.

I hope this make some sense

I think it makes sense although I never knew they existed or noticed them before.

I can't work out where your picture is from though. Is that looking in the boot and if so, whereabouts? Are the air outlets those two squares left of centre?

 

[Honda-atr]

Its in the boot on both sides. You see the opening, behind that opening is the air outlet. One at each side.
The picture is taken looking at the left hand side of the boot. You can see the wires runing from my left rear light

 

[Rom]

Those are air vents. Have one each side. They are slatted, with a rubber type membrane attached at the top. This makes a flap, which will flap around.
They allow ventilation, and allow for pressure change when closing doors and boot etc. When you close something, the pressure escapes through the flap.

You need to remove the rear bumper to remove them. They unclip from the inside, and come outwards towards the bumper.
It's possible yours are broken, the flaps damaged etc.

Sent from my SM-G928F using Tapatalk

 

[Linus27]

Those are air vents. Have one each side. They are slatted, with a rubber type membrane attached at the top. This makes a flap, which will flap around.
They allow ventilation, and allow for pressure change when closing doors and boot etc. When you close something, the pressure escapes through the flap.
You need to remove the rear bumper to remove them. They unclip from the inside, and come outwards towards the bumper.
It's possible yours are broken, the flaps damaged etc.
Sent from my SM-G928F using Tapatalk

So if they allow for pressure to change when closing doors etc. and mine are broken, do you think it's possible that pressure could build up enough to make a window explode? The reason I'm asking is the other month I was driving and for no reason at all, my passenger window exploded.

Also, how do I know if they are broken? Would the flap be open or permanently closed and would they make this fluttering noise? Sorry, lots of questions

 

[Rom]

I doubt they would ever cause that, especially whilst driving.
The pressure mainly changes when you close a door or boot.

You can get your hand on them and see how secure they are. If they rattle around, maybe that is contributing to the noise.
The flap could be torn, or come away at the top a bit etc. I'm only guessing here. But if you are sure the noise if from that area, that's about all there is behind there. That, and the bumper location bars. They are screwed to the car. So less likely to be them.

Sent from my SM-G928F using Tapatalk

 

[Linus27]

Ok thank you.

Can I get my hand on them by putting my hand under the bumper and having a feel? Still not 100% where about they are. If the number plate is in the middle, where abouts are they in relation to that, under the brake lights, or further out under the indicator?

 

[hondamad2204]

Its the black rectangle here.



One in the same place on the other side. Easier way to inspect would be from inside removing the trim around the boot..... But having said that, the rear bumper is a doddle to take off too

 

[spooke]

Ok thank you.

Can I get my hand on them by putting my hand under the bumper and having a feel? Still not 100% where about they are. If the number plate is in the middle, where abouts are they in relation to that, under the brake lights, or further out under the indicator?

 

[Linus27]

Amazing thanks guys, I know exactly where you mean now. Will inspect when it's not chucking it down.

Is it possible or known for these flaps to make some kind of noise?

 

[hondamad2204]

They are the flimsiest peice of rubber you will come across. Lol if its torn it could be that all your hearing is outside noise un filtered if that makes sense. ? There really isn't anything there to make noises bodywork wise other than that...inspection will be your only way of finding a cure. But no, ive not know one to "fail" as such.

Just thinking...you say it moves from side to side, its not water in the boot is it? Sloshing over and out these flaps...it's possible.

 

[Linus27]

That's a good call on water as my boot does get water coming in when we get heavy rain. I will check it out. The only thing is the noise really sounds like fluttering and not very water like. Plus I can force the sound by reving to 4K and letting them drop. Might see if I can record the sound.

 

[Linus27]

So, I got to the bottom of the noise. It turns out to be pickup from my tyres coming away and either hitting the underside of my car or bouncing around the wheel before flying off. I was at Spa last Tuesday doing a track day so that's where it's from. I didn't notice it before but after inspecting again in more detail, there's lots of thin rubber strips stuck in the grooves and on the face of the tyre. So the tapping noise is like when you put a card on a spoke of a bicycle but in this case, it's coming away from the tyre hitting the wheel arch and the underside of the rear of the car before flying off for good.

Thanks for all your help guys. At least nothing sinister.

 

[Kevin85]

I was going to suggest it could be pickup/your own tyre, but the conditions you described were quite specific.

 

[Linus27]

I was going to suggest it could be pickup/your own tyre, but the conditions you described were quite specific.

Yeah, surprised I didn't think about it before. Never had it quite this bad before and I would of thought I would of heard it driving back from Spa and during the week after.