[Christ]

Frank - Yes, diesels experience knock, but it's a different symptom. Over advancing the fuel pump can cause it (Injection too far before TDC, kind of like ignition over-advance.).

Too much heat (I mean REALLY hot) can open up the cylinder walls away from the pistons, making too much clearance, which causes piston slap, which sounds like knocking. This typically happens when the cooling system can't keep up with overheating cylinders, the upper ends of the cylinders will expand slightly, giving clearance to the pistons to slap against the cylinder walls on compression and power strokes (due to stresses). It's a semi-metallic clack noise (different than the normal diesel clack) that usually indicates that your pistons/rings are about to grenade.

I'm aware that diesels run on the knock principle, however, they do it in a controlled fashion.