Catalytic Converter

[xx-Trev-xx]

Hey, I've searched google and JC before making this thread and couldn't find anything relevant to the issue i'm having. The catalytic converter on my VZ Berlina has been making a loud rattling noise during a cold start, it usually last for a few minutes until the exhaust becomes warm. I know that it isn't the heat shields as i have removed them and am 100% sure the sound is coming from the Converter as i have gone under there and checked while the car was running.

While hitting the exhaust and catalytic converter with a rubber mallet, there were no rattles at all and everything seemed normal, i found a broken exhaust hanger however i have since fixed that. The car does run normal although whenever i start the car it's always inconsistent e.g sometimes it starts perfect, sometimes it shudders and other times it will take a few seconds longer to start than normal also thick white smoke sometimes appears even when car is warm but disappears after a few minutes of driving, there is no check engine warnings and last time when checked with a scanner no fault codes came up concerning the O2 sensors.

I'm curious to know whether or not the catalytic converter is actually damaged or not as i don't care about the sound too much as long as it doesn't have any harmful effects towards the car in the long run and if anyone else has had a similar problem that they have fixed. It's quite frustrating as the engine was replaced not long ago and now more problems continue to occur with the car. Any help would be greatly appreciated.

 

[Dirbatua]

you sure the noise is coming from the cat?

sounds more like the rattling noise on a cold start would be coming from the rockers then the cat.

Cat rattling normally occurs when the **** is loose inside at high rpm (mine used to rattle **** around after 4000rpm or so until i replaced em)

Does the white smoke have a pale bluish sort of tinge to it or smell like fuel?

and how many km the VZ done cause those alloytecs build sludge like nothing else.

 

[xx-Trev-xx]

Yes, can definitely confirm it's the cat, was right under it when the car was started and got louder the closer i went to it.

At first i thought the noise was from the engine but can confirm it's from the exhaust. It's coming from underneath the car rather than front of the car.

Mine only rattles during first start up and last a while until it gets hot after that the sound is still there but it's not as loud.

It's not bluish but it does smell like fuel, I've checked the spark plugs and have notice there is some black build up on them so will be replacing them soon.

The car itself has 203000km however the engine has only done around 140 000km according the the guy at the wreckers.

I don't think it's sludged up as it's serviced on a regular basis and there isn't any performance loss or anything unusual besides the start up and rattling noise.

 

[Not_An_Abba_Fan]

Get a socket onto the flange nuts that hold the engine pipes to the manifolds. Sometimes they come loose and sound exactly like a cat rattling. If the cat was stuffed enough to rattle, it will rattle whether hot or cold.

 

[xx-Trev-xx]

Tried tightening all the bolts throughout the whole exhaust today, still no luck. I've notice that it sounds more like the exhaust is rattling against something rather than it being inside but not 100% sure. As there isn't anything near the cat that it would be rattling against. I was thinking it may be the O2 sensor as the car is running rich however there isn't any messages coming up in the dash.

 

[xx-Trev-xx]

Still having this issue, thought i'd post up a video of the sound to confirm if it's the cat before i decided to spend $900 to replace them.

 

[xx-Trev-xx]

 

[Ozzy]

Interested in this topic as my car does the same on a cold start for a minute or less. I've just brushed it off since it goes away will be interested in the outcome

 

[Group C]

Had a similar thing on my VZ v6, got underneath thought heat shield removed still there, defiantly sounded like rattle from CAT, but ended up being the small heat shield right up top between exhaust flange and P/S rack bent back a little with screw driver all fixed, hard to see shield but check it first mate