I’m another new person to the forum and would like to get feedback (anyone else had this issue) on the problem I’m having.  I have an 03’ Excursion, purchased in May of 2003.  Which, according to every forum I’ve read means I have a pre May 2003 6.0 diesel and I get the impression that can be a bad thing.  I have had the usual warranty items replaced: one turbo, 2 fuel injectors and several computer code upgrades (I know this is minor compared to others, but I won’t get into the two times I had the Rear Diff. partially rebuilt by Ford).  We took a 2800 mile trip from Colorado to Seattle and started with 99,700 miles on the odometer.  On the return leg when I was about 40 miles from my house I started seeing medium grey smoke in the mirror (not as dark or as thick when compared to the smoke from the bad fuel injectors).  I pulled in the driveway and noticed the at-rest idling exhaust sound was now doing a “thumph, thumph, thumph” sound, instead of the normal diesel purr.  After letting it set for a few days I started it and it still does the “thumph, thumph” sound for a minute or two between 4-5 minutes of purring.  I have started it several times since then (still starts great) and it’s still the same thing.  I have noticed that each time I start it I have fine black soot, like black baby powder, shoot out the exhaust and onto my garage floor.  During the trip I averaged over 19 mpg and had no problems until I was 40 miles from the house.  Each fuel stop was at a name brand, typically a Flying J truck stop.  Other items of interest: I had Ford change the oil just prior to leaving, all fluid levels are still normal, temperature changed with each state we went through on the way back – in the 60’s in Oregon to below freezing and 10” of snow in Wyoming, then back to the 60’s in Colorado.  The only time we stopped on the return trip was for food and fuel, 1400 miles and 20+ hours.  I know that it is at least one revision behind on the computer code, the code I have is the one that makes it “buzz” for 30 seconds after turning it off.  I have a short video clip (with sound of course) of the exhaust doing the “thumph, thumph” thing that I can email if that will help.  Before someone gets on the Dodge Cummins bandwagon, let me remind you that Dodge does not make an Excursion equivalent.  Any feedback would be appreciated.  

Email me that clip at jgray1@myvu.vinu.edu and I might be able to help you out with it.  I need to see it first and I can probably help you figure it out.  Oh and the cummins boys can shut up because in the truck on truck pulls this year in Lima Ohio the powerstrokes pulled the *** out of the cummins!  

could be egr cooler or head  gaskets if it is the cooler if you pressurise the cooling system you can sometimes hear it hissing with ascrew driver in your ear or a stethascope  tbird