D3 knocking under acceleration from low rev

[skyship007]

Originally Posted by nielsthorsen

Unfortunately I have not solved the knocking problem. Is is still there on at hot motor but only in the sommertime.
Niels

I would get the hidden fault codes read if possible (Might be one tooth out on the cam timing or have an injection system fault code).
If there are no codes, then try fully servicing the engine, including using a direct feed injection system cleaner like Liqui Moly Diesel purge when changing the fuel filter.

It does sound like worn main bearings or low oil pressure from sludge obstructing the oil pump feed.
Try moving up one oil grade to an 0 or 5w40 full synthetic that cleans well.
Shell Ultra is probably the cheapest option.
Finally, see what happens if you reduce the oil change interval in half (No need to change the oil filter until the normal interval) to help clean up the block.

It's also worth checking to see if the Aux belt tensioner or even the alternator pulley are causing the rattle. Just remove the belt and see if it still occurs. Even a lose manifold or downpipe can cause a temp dependent rattle.