Originally Posted by DallasGV

Timing chain guide rail failure, page one of my post - http://www.xoutpost.com/bmw-sav-forums/x5-e53-forum/83842-video-sound-money-coming-out-my-pocket.html

Originally Posted by DallasGV

On second thought, if that is the sound your engine is making I would NOT run it even to check the replaced tensioner. Why? Because when you replace a tensioner and start the car, it takes several seconds for it to build up oil pressure to "tension" the chain. And, in those brief seconds if your guides have started to disintegrate it could give the chain even more slack which might allow it to jump some teeth which would be very bad. I'm not sure about this, so hopefully some others can jump in and give us their thoughts.