Whilst driving the other evening I accelerated to find the car did nothing but start spitting out blue/black smoke from the exhaust. It became more frequent switching between running normally and then jolting/bucking and smoking prefusely. It then went into limp mode and engine management light came on.

So I had the car towed to a garage and the mechanic eventually decided to take out the EGR and give it a good clean, assuming the rotator valve had gotten stuck due to carbon build up.... only to find that the valve had entirely snapped off the rod it connects to to enable it to flap open/shut and lodged itself inside the exhaust tube the reroutes some exhaust back into the engine.

Now.. I had to have the EGR replaced completely which was fkin expensive but necessary... thinking id be covered on the warranty for the price as i bought the car a month ago and its under 3 month warranty with the dealership i got it from. Then to be told that that particular part was not covered. I then looked at the T+Cs of my policy and it states that EGR valves and turbos are not covered IF the fault is due to carbon build up.

In my opinion, the valve snapping off completely is jack **** to do with carbon build up!!! thats surely mechanical faulire. but I am also not a mechanic or in the know of what damage carbon can cause... so therefore please could I have some honest answers as to whether carbon build up can cause metal to snap off!!!?

Ill be honest with the fact that the car has done 118,000 miles and i dont know in what way the car was driven by previous owner but i drive it softly and not harshly. so what do you think as im currently arguing the toss with the company to pay it for me. Ive had the mechanic and an AA mechanic i know both say that its highly unlikely for carbon to wear metal to snapping point.

Any views welcomed, thanks guys