Just did the complete fuel line replacement, delivery valve seal change, and glow plug replacement change on my '99 E300D with 110K. At first I got some godd nailing after intial startup but it went after after a mile or so of driving. Now 120 miles later it came back today after pulling off the freeway, then went away after a mile or so. I thought the first incident was due to the air working it's way after the fuel line replacement, but now I am not sure. Could it be something off with the the delivery valves? It never made this noise prior to the maintenance.