Hey, I just learned that my exhaust valve on my 4th cylinder is broken and will need to be replaced, so I was just wondering how offend this happens and what might have caused it to break in the first place. Just so you know I am a reasonable driver, no racing or anything like that, although I do drive it hard sometimes, and also I live in Upstate New York where the temp can get will below freezing at night, thanks a lot and hopefully I can avoid this in the future.