WayneCallar

This was my CAT in the end. Jack car up enough to reach CAT, bang it with a spanner and hear it rattle!


Car was fine yesterday, today a terrible rattle! I pulled over straight away in fear of of being engine related! Satisfied the noise is coming from the mid/back of the car I've gone out to get some vids.

To me, it sounds like a bit of the exhaust rattling around? Or an exhaust heat shield? I have an Invidia Q300 installed atm with stock cat.

It mainly happens when accelerating and a lot quieter on deceleration. Not sure how these vids turned out. Please excuse the trouser/trainers, just on the way to the gym!

Has anyone else experienced this? Upon research some people have said the TCT going gives a similar sound?





Thanks,
Wayne

HvRRZ

possible exhaust rattle. Take out the secondary O2 sensor and check the inside of the CAT. Could be the inside of the CAT has come loose.

WayneCallar

Will I need to take the cat off to check that? Is it quite obvious if the inside has come off do you think?

WayneCallar

The scary bit:

When cruising in 2.5-3.4k, say in 6th gear, it can be silent. As soon as I press the throttle just a millimeter, and before the car even start to increase in speed at all, I get the buzz/rattle. What can that be!?!?!? I'm talking instantly...!

If it's something to do with the exhaust then I'd imagine I'd get noises when going over bumps etc which I'm not.

onu2002

To check the cat, get the car up on jack stands as high as possible. You'll have to crawl completely under the car. Remove the O2 sensor from the cat. You might have to reach up and disconnect the wire harness to be able to completely unscrew the sensor. Pull the O2 sensor out, shine a light in the O2 sensor hole, and bang on the cat with your fist or a mallet. You should be able to see if the "guts" of the cat are loose or not. There's a video on Youtube that shows this.

You don't need to remove the cat for this, just the O2 sensor.

WayneCallar

Thanks mate. Appreciate the guide and will hunt for that video! I never hear the rattle/buzz going over bumps or uneveny road though which you would expect from a loose part in the cat? Also I hear the noise instantly upon very light throttle. I'm not sure that miniscule increase in air flow through the exhaust would instaly cause it to rattle?

onu2002

I don't remember under what conditions I could hear my rattle, but it wasn't constant.

http://www.youtube.com/watch?v=_jk48X85LsM

Reckon

Start with the cat as others suggested. You won't necessarily hear the rattle over road bumps since it is probably affected more by exhaust volume than anything else.

Your sensor itself might even be loose from the cat (happened to me a few weeks ago, but I have a test pipe and sensor adaptor for the CEL fix - the adaptor just got loose and was rattling at low rpm, around 3k, and when given throttle).