Stock engine no mods 240K. Rebuilt FICM, Runs well idles smooth but has thumping noise from intake ,which begins 2-3 minutes after cold start, and immediatly after hot start. Have visually checked rockers and pushrods. No indication of bent pushrods or broken rockers. All valves seem to be operating normally,no thumping from exhaust any ideas?

 

Can you make a video with the sound. Not able to understand what sound that is and where it is coming from. Thanks

 

will try to video later but sound is similar to the typical sound 6.0s make when they have a bent pushrod but without any lifter or valve clatter. Similar to sound of helicopter rotors or slow speed diesel intake pant. sound is coming from intake at front of vehicle only.