I have no idea how to describe it. 2001 LHS, I just replaced the plugs and a coil but doubt it has anything to do with this new noise.

It has been operating fine but last night when my wife pulled it into the garage, a very loud noise came from under the hood. I have never heard anything like it in my life. No lights came on to indicate a problem and when I started it back up in a few minutes, the noise was gone but started again after a few minutes. I looked under the hood and can not pinpoint the source but it is so loud and unpleasant I didnt let it go on long. I waited a while and started it and the noise was gone and I let it run for a while and no noise again.

What would do this? I checked all the fluids and they are good. Power steering seems fine, trans seems good. No problem starting. I am afraid to move the damn thing and its my only vehicle.

Help

 

Did you check the alternator? Also check the belt tensioner/pulleys, as they may have thrown a bearing. Hard to really know without hearing it personally.

 

I have a 99 Concorde and it is doing the exact same thing as your car is. I can not figure out how or what is going on under the hood. It sounds like a loud muffler noise under the hood.