[:@] I have a 2004 Disco with 33000 miles, two weeks ago I noticed a slight tapping noise, by the end of the week is was very noticeabek at idle speeds. I took it in for service and I am being told it is the catalytic converter...the noise sounds louder just out side the car by the drivers fender near the ground.
To me it sounds like vlave or roacker arm noise..it goes away if you reve the engine...only does this at idle after the engine heats up??? Anyone had this problem?

 

It could be Cats, they will rattle at low RPMs.
What you need to ask the dealer is what caused them to fail cause you will want that fixed also.
Mike

 

I agree. Just check to make sure your headsblown out on you. Oil, coolant can melt your cats causeing a ticking noise and eventually leading to emissions past threshold. Crawl down under your truck while its running and give it a good ear. It's not too uncommon for cats to go out on rovers. Let us know how it all turns out. Regards.