Hi. I figured we older Olds lovers might also drive new ones too. So, here goes. My friend has a 1998 Olds Aurora. He is getting a periodic low knock or thumping sound at hot idle. It seems to be coming from the passenger's side lower part of the engine. The car has about 75,000 miles on it. Any ideas what might be causing this? One other question....does anyone know if the harmonic dampener on this engine can be changed without major surgery, in case that is part of the problem (not saying it is, just curious. Thanks for the help!