Does a cat converter which is probably past its prime give any warnings before a complete failure and loss of power? I have a buzzing noise which I thought might indicate early blowing of the exhaust but there is no problem with the main body of the system. The noise is up front near the manifold.
agree that it sounds like a heatshield. it is possible that the insides of the cat is coming loose. best thing to do is trace exactly where the noise is coming from.
btw, toureman, if a cat collapses inside, it causes the car to feel like its 'strangled' and will get worse the further you drive, ie as it gets hotter.
Thanks to you all. The vehicle is a 99 Mitsubishi Carisma 1900 DOHC and the converter appears to be situated just for ward of the front seat well. There is a short front pipe between the manifold and the converter and, I think, a heat shield under the well.