Thudding Exhaust Tone, No Pressure From Exhaust

[paramaniac]

Hi all,

I've got a 2009 Focus 1.8 petrol, in the past couple of days I've noticed my exhaust tone change slightly, sounds a bit deeper and thudding slightly. Especially when engine is cold or if I accelerate from very low revs. Also when I cover the end of the exhaust there is no pressure pushing back on my hand. This leads me to believe that the exhaust is blowing somewhere.

However I thought maybe there is some safety mechanism that allows exhaust gases to escape if the end of the exhaust is blocked - hence no pressure and it's supposed to be like that?

Not noticed anything else wrong with the car. It's still within the 3 year warranty so I'm dropping it off at my local Ford dealer tonight. Just wondered if anyone had similar experience and whether it was rectified under warranty without any issues?