One of our 7.3 is makin a thump sound under the hood when first started in the mornin, it only lasts for 2-3 seconds, but it sounds like its coming from the drivers side, the truck runs great no problems, it has a donaldson airfilter and 4 inb exhaust any ideas on what this could be, truck has 205,000 miles.

 

If the noise is coming from under the hood it's likely the EBPV, most just unplug it.

If the noise is coming from under the dash it's may be the in the HVAC. A small vacuum leak can cause it. Put the switch to defrost and shut the truck off. start the truck...if the noise went away, there's your problem.