rattle noise ? cat?

[foxy197]

hi all have developed a rattle tin metal sound when engine revs are reducing and is heard when revs drop during gear change, been under car and shaken exhaust can make this noise by tapping the CAT, got no warning light and just passed mot few month ago no probs wif emissions, bet these fings are expensive?
hope its not on way out, any input apreciated Thanks :coffee:

 

[Foxspeed]

if its rattling from the cat then the "monolith" internal structure is loose or has started to break up either way its a down hill condition leading to a new cat - assuming it is actually coming from there as the sound can travel

 

[foxy197]

argh bet these are expensive arent there two of them?

 

[Ed...]

Cats are expensive but how many miles has ure car done and i take it its 3 years old as u mentioned an MOT?

 

[foxy197]

yeah its 2007 on 56 plate, 40,000 miles

 

[foxy197]

helllllllllllllllllllllllllllllllpppppppppppppppppppppppppppp

 

[Foxspeed]

argh bet these are expensive arent there two of them?

it will only be one of them if your lucky - thing is it passed the mot and emissions test so you have 12month to sort it

you can either go for an oe replacement or get a universal one i would of thought either way not just a couple of £££

look for a scrapped one - probably pcik one up for a good price

 

[RalphyBMW]

I would make sure it isn't a loose heatshield before worrying too much. Used cats come up quite often when someone changes their exhaust for an aftermarket option, as Si said you have 12m to sort it. First rule out loose heat shields then keep an eye out for a used cat, possibly as part of a full system.

 

[foxy197]

thanks looked at heat sheilds appear find guna look out for second hand cat appears to be the one nearest back of car?

 

[brightside]

are you positive its the cat?

I could of swore something was rattleing in the exhaust in mine aswell, only seemed to happen though when "rev matching" ie, coasting, blipping the throttle.

Turns out its just "popping" in the exhaust, its nothing to worry about, its just the noise they make. Mines done it since I got it, and I'm not worried. If its the 2nd cat if it is going, just get it decatted. Should still scrape through an MOT with the 1st cat still there, the flat spot will be there when you decat it, but you never feel it really as its between 2-2500K revs. Only time you feel it is if your labouring the engine anyway.

HTH