My friend has a 79 300 SD. He has a loud clacking sound as distinguished from the normal klata klata.
The car runs fine starts easily and suspecting injectors he replaced them with no change.
He says that the noise tends to be worse if the oil level is high rather than low.
He also reports that the noise does not seem to be coming from under the valve cover.
Any ideas of what the cause of this noise might be?