My 03 MCS has become “louder” recently. When windows down and driving next to a center divider or a wall, it sounds louder compared to before… A test drive with the shop foreman of the dealer resulted in “I don’t hear anything abnormal” :impatient.

In addition, now there is a "squeak" type noise. I can’t easily locate it, but it starts after driving about 5-10 min (it is not there when I start the car in the morning). Once it starts, it feels like a "bird singing/chirp", and it is there whether I put the car in neutral while cruising at any speed or moving through the gears. When I reach work and park the car, I keep it running with bonnet open and try to locate the noise in a quite parking lot. It is singing like a bird, and it seems like it is coming from somewhere "under the car".

The person who installed the pulley today said that it is exhaust-related and most likely the catalytic converter is rattling/squeaking. He apparently heard the noise echoing from a wall next to the road.

Here is the question. Does this sound like a symptom of a failing catalytic converter? What can I do to diagnose it further? Unfortunately I don’t have a garage and the tools to put the car on jacks and “see” what’s going on.

The good thing is that based on California Emission Control System Limited Warranty catalytic converter is covered for 7 years or 70,000 miles (whichever comes first).

Thanks very much for any input.

 

by louder what exactly do you mean?
is the exhuast tone louder? could it be cupped/feathered tires?

now about the squeaking noise. you said it happens all the time after the car has been runing 10 or so minutes, does the sound get louder when you apply the gas pedal? can somebody apply the gas pedal while you listen outside of the car?

if so you can kneel by the doors and listen, that's where the cat. converter
is at. if it's an exaust leak you should be able to hear a difference.
good luck.

 

I dont think it is the tires, because if I put it in neutral around 60 mph the "loudness" goes away and it becomes more evident when I floor the gas pedal.

The squeak does not get louder when pressing the gas pedal. Actually, it seems to be easier to hear it when I let go off the gas pedal. As I mentioned, it is very clear in the parking lot as well - not moving. It feels like an intermittent squeak from a loose connection somewhere....

Thanks!