Farty cat...

[Rmachines]

the exhaust on my 1.8 is noisy but its not blowing,  and its not the silencers.   I will say that first as its hard to explain!

It sounds like a blowing manifold or down pipe, but not loud,  there is a tinney sort of noise under acceleration and idling, which makes the car sound very ...rough.   It sounds very much like the cat area,  no noise from the manifold or downpipe.   Its like i can here the loud sort of sound from what would be inside the manifold puttering away into the cat, like the metal is to thin to keep the noise at bay, Its a stock VW cat which is not rattling or anything..... hard to explain but .... does any one have any idea why/what or how to stop it?   I have confirmed there is no blowing or leaks on the exhaust system. it just makes it sound so rough. 

[tweed]

dead cat. it must stink 

[dan_apps]

mine does the same but has a brandnew cat i think it might be the downpipe on mine, doesnt annoy me enough to pull the fecker off though tbh.

[Jack3559]

[javalin]

have you checked the heatshield on the downpipe?  If it rattles, can sound like a blow.

[Len]

There is also a heatshield below the CAT.

[Rmachines]

Hi, the noise is not like a rattle, and not like a blow as such.  I have pressure tested the exhaust, and doesnt leak atall, just builds pressure to the point where it blows my hand away. 

This is deffo a manifold sort of sound, but its muffled,  basically its a tinney, noise like the explosions from the manifold are heard through the thin metal casing of the cat,  but .. it shouldnt.      Rarther like that of a leaking manifold or downpipe really, but the noise is from within the cat its self ?!?

[spudboy6]

thread revival here ! thankyou search button .

did you ever get to the bottom of this , your post basicaly saves me starting a thread as i have the same ,

when i fire the car up from cold . there is a loud ticking coming from under the front by the car area but not present in the engine bay i must state ,

but it does this for about 30seconds of idle , then the revs start to drop as i presume "cold start " goes off . and the noise gets quieter untill the car is warm and disapears .

like above have full 100% pressure

when its doing the noise if i rev the car up the noise seems to go away at about 2-3KRPM but is still there ,

im wondering if there is something on the manifold to do with a cold start valve that takes exhaust gasses for warm up possible making the noise ?

strange thing is when its stone dead cold its present when next to the car , but when its up on the ramp with me under it i cant find it ! , head shields have all be checked front back bhind steering collum bottom of cat back box center box ECT not a rattle

ill try get a video in the morning ,

but any soloution ?

thanks guys .

[thai-wronghorse]

Sounds like a cracked exhaust manifold to me.  It took months and several garages to diagnose the one on my  8v a few years ago.

Another thing to check is the rubber bellow that surrounds the steering column universal joint where it passes through  the bulkhead. If this is split it will transfer exhaust noise into the car giving the effect of a dodgy manifold or downpipe.