more clacking than normal

[roadracerex]

So on startup with my early 99, it sounds like one cylinder is clacking louder than the others. I was thinking exhaust leak, but I am not sure. The clacking follows engine rpm and is just louder than the normal diesel noise. There is no smoke on startup and it idles fairly well for 180k miles. It also accelerates fine when I drive it and the noise goes away (almost) when it gets warm. Just started noticing it since it is getting colder. I checked the glow plug relay voltage and the resistance of all 8 glow plugs and they seem fine. Anyone?

[bob harris]

noisy tappet ?? needs adjustment maybe