I have a 2003 Discovery that I have owned for about a year. Last night it started making a real loud knocking noise so I drove it straight home. This morning I took a look and couldn't diagnose the exact cause, not sure if it's a blown head gasket or what. Anyone ever heard a Disco do this? Not sure if it's even safe to drive to the garage.

 

sound like exhaust leak. possible head gasket, possible busted manifold. you should be able to locate it, it is going to be down at the head area
edit; manifold bolts all there? you can stick your hand down there, before it gets hot. you will feel it blowing on you.

 

Found the problem, a sparkplug wiggled loose and decided to do a combat jump out of the engine. Picked up a new plug, fired her up and she is purring like a kitten! Thanks for the suggestion, I was looking over the manifold bolts and saw the sparkplug wire out of place.

 

well that will do it

 

I had one loosen up on my truck a while back. The previous owner had replaced the spark plugs but I would imagine they weren't tightened with a torque wrench. I highly recommend using one on the gasketed plugs on these aluminum heads.