Cummins sounds like a rod knocking when cold.
Here is someting to consider from a Dodge Technical Service Bulletin (TSB). See what you think.
It sounds like the T-stat may be causing the problem. According to Cummins, especially in the 3rd generation 5.9L, the cold engine will knock until it warms up. My 2006 does this as does my 2001.
Here is something else to consider should you hear a knock while towing.
Models -- ‘98 - ‘02
Engine knock or rattle sound when climbing a long grade and towing a heavy trailer.
This bulletin applies to 1998-2002 Ram trucks equipped with the 24-valve Cummins diesel engine (sales code ETC or ETH). Owners may experience an engine knock or rattle sound when climbing a long grade while towing a heavy trailer.
If the condition exists, replace the engine thermostat as outlined in the service manual. Note: Mopar 05015708AC is to be used exclusively for this service bulletin. Use thermostat 05015708AB for all other 24-vlave Cummins thermostat repairs.
Last edited by jrconsultid; 11-07-2013 at 11:30 PM.