Exhaust Rattling/Vibrating Sound

[OKLY]

Dear all experienced car enthusiasts,

I've recently changed my MyVi 1.5's exhaust system to a full set stainless steel exhaust. After changing the exhaust system, there's a rattling/vibrating sound coming from the rear. It sounds like a metal touching metal sound. It happens when the car is idling, when I rev it there's no sound until it is at the idling RPM again.

Problem is this happens randomly so whenever I drive back to the exhaust shop, they cannot detect the problem as the sound does not happen. However, based on my observation, it usually happens when it is cold. Morning there's a bit of sound and also during night it's kinda loud which I suspect it happens when it's cold. As I'm quite far from the exhaust shop, it is inconvenient for me to keep going back and couldn't solve the problem.

It is also louder coming from the rear (so rear passengers can hear the sound more obvious).

Any idea what could be checked to solve this problem? Could it be because when it is hot, some metal expand so there's no sound?

 

[l2s_turbo]

Bro, when you fix up ur new pipe, did they include the flexible pipe for you? That thing will eliminate the sound too..

 

[OKLY]

Hmm... Not too sure about this. Not very knowledgeable in exhaust but because the shop gained a lot of positive feedback so I trusted them.

Anyway, how will the flexible pipe help for the sound? How does it work?

 

[l2s_turbo]

Hmm... Not too sure about this. Not very knowledgeable in exhaust but because the shop gained a lot of positive feedback so I trusted them.

Anyway, how will the flexible pipe help for the sound? How does it work?

It helps to reduce the vibration by acting as an absorber throughout the pipe.. it normally fix at the end of the extractor connecting to the middle piping..

 

[OKLY]

If let's say they did not use the flexible pipe, can it still be added now?

 

[l2s_turbo]

If let's say they did not use the flexible pipe, can it still be added now?

Can why not? Just cut and add in between.. btw maybe you try check whether did they fix or not? You try peep below your myvi see..

looked like pineapple one..

 

[OKLY]

Like that I think need jack up the car only can see, very hard to peep from under, car quite low. Thanks for your input!

If let's say they did not install it and after installing the flex pipe also same problem, where else should I look at?

 

[l2s_turbo]

the stock mountings that holding up the exhaust..you can change to those hard type.. "red colour" mostly la.. those are for turbo engine use as it vibrates more than NA type.. after using that i think should not be any sound left gua.. unless that guy never properly secure your exhaust.. one more tip is, once you changed your pipes, it's advisable to retune your ecu, let it recognise this pipe.. else you will encounter high fuel consumption later..

 

[AD_EG]

bro sometimes its the close to the rear, when they do the piping, they never check properly if it touches or hits anything once you start driving, usually at the muffler area, check and see at that part...try to move the muffler with your hand(when car has not been started or parked for a long time) and see if it hits anything like the arms, maybe anti roll bar etc...i suspect its somewhere there..

also like bro l2s mentioned check the rubber mounting/holder thing also

 

[OKLY]

the stock mountings that holding up the exhaust..you can change to those hard type.. "red colour" mostly la.. those are for turbo engine use as it vibrates more than NA type.. after using that i think should not be any sound left gua.. unless that guy never properly secure your exhaust.. one more tip is, once you changed your pipes, it's advisable to retune your ecu, let it recognise this pipe.. else you will encounter high fuel consumption later..

Thanks a lot for the tips. I'll drop by to their shop this Saturday again.

Check list:
1) Check if they used a flexible pipe for me.
2) Check the mountings.
3) Reset ECU and hope it does miracle.

bro sometimes its the close to the rear, when they do the piping, they never check properly if it touches or hits anything once you start driving, usually at the muffler area, check and see at that part...try to move the muffler with your hand(when car has not been started or parked for a long time) and see if it hits anything like the arms, maybe anti roll bar etc...i suspect its somewhere there..

also like bro l2s mentioned check the rubber mounting/holder thing also

Good point, yea I suspect it might be the muffler box as well because from what I can hear, the sound is loudest at the rear right hand side whereby the muffler box is the closest (for MyVi). Have to check if it's touching the anti-roll bar or not as well, did not check on this. Well when I went back to their shop, their foreman did try hitting all possible parts but did not came into contact with any parts of the car (but this was done when the car was already kinda heated up).

Any idea how I can let the exhaust system cool down faster?

 

[DanzEterna]

i guess it should be 1 of the exhaust rubber mountings

 

[AD_EG]

if it happens when driving when you hit bumps? maybe when you hit and the abosrbers compress it hits something ? when the foreman jacks the car up, it might not ocme in contact with anything cause the car aint moving..

 

[slipar]

if the exhaust system not touching anything..
maybe something loose inside the muffler..
when cold not expand yet so got rattling..
but when hot expand so no rattling..
my wild guess only..

 

[OKLY]

if the exhaust system not touching anything..
maybe something loose inside the muffler..
when cold not expand yet so got rattling..
but when hot expand so no rattling..
my wild guess only..

Yes this was what I suspect and told the shop too but they told me that if something is loose inside the muffler, whether it's cold or hot there will definitely be a sound. Hmm..

They welded an additional clamp to hold the exhaust pipes tighter and there's still the sound.

I noticed one thing though which is really weird, during night the sound will definitely happen while in the morning (I usually start moving around 7.30am), the sound is there but not as loud compared to night time. For night time, even if the car has been running for house (so I believe the exhaust system has been heated up), the sound will be there.

This leaves me wondering that it might not be related to the temperature. But heck, why is the sound more obvious at night even when the car has been running for hours already?

 

[AD_EG]

was your window up at all times?

driving style same at night and day?