Got a 1999 Dodge Ram 3500 dually 24 valve Cummins, have a super loud knock coming from what seemed like the intake horn. Have checked the horn to radiator connection, nothing was lose nor inside. The plenum and horn had a lot of carbon build up but nothing that seemed to be alarming. I am stuck and haven’t seen anything online that has helped me individually.

Its real loud and knock type sound for sure. Loss of power and has small amount of black smoke. I went through a medium deep creek crossing a little while before it started doing it also if that helps.

I will put up a few second video of the noise up tomorrow so you can hear. Had my neighbor who is a gas motor mechanic say he doesn’t think it’s a rod.