I've always heard it called injector knock or diesel knock until this last year, here on MercedesShop. English is a living language!

I prefer injector knock, as it is more descriptive. After you've been around these beasts for a while, the various sounds become distinct. It is possible to distinguish between injector knock, rod knock, and a low compression knock when you have heard them enough, and know when they are loudest, etc.

Any direct injection (mechamical only) diesel will have that characteristic rattle. They newer CDI/TDI engines have electronic controls, and inject a tiny bit of fuel, then the main charge, so there is very little knock. They also have a "prechamber" in the piston -- seems to work sort of like a power cell diesel/prechamber with the power and fuel economy of a standard direct injection diesel, but without the noise and smoke.

DieselNation most probably has a combination of bad injectors and low compression knock on the last two cylinders -- that "low thudding" accompanied by a ringing noise that goes away at high speeds sounds just like the 220D, and I know that is low compression -- excessive blowby and tight valves before the last adjustment.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!