C250TD Big end noise

[SSBB]

Hi all,
Ive just bought a C250TD estate and took it to wales for a good run. While going up the Snowdonia mountains I heard a worrying noise which I recognised immediately...big end knock. It came on suddenly and was very pronounced, I eased straight off the gas and took it steady for the rest of the journey (100 miles). The car was left to stand for about four hours before we made our way back and...no noise.
Any ideas?
The noise was only under load, the oil level was correct, 84000 miles and full MB history, last serviced a month ago.

Regards
Shane

 

[Dieselman]

Check with a stethascope whether it really is big end knock. These engines can make some very frightening knocking noises, which transmit through the whole engine frame, just from a faulty injector pattern.