Originally Posted by barry123400

To establish the affected cylinder just loosen each injector nut. The knock should lessen or dissapear when you hit the right cylinder. Most problems on the 240d have been the #1 cylinder. If that turns out to be the case you can drop the small forward oil pan. This will allow you to remove the rod cap and see if the crank is damaged. If it is not tore up perhaps the expendature for a pair of bearing shells is worth the risk. Since the engine was not truly out of oil although dropping to three quarts is not particularily good. It might have been somewhat co-incidental. Did your sister observe no oil pressure at any point? Do mark the rod and rod cap before removal. Nothing much to loose. I would not drive or rev the engine as quite a few 240ds have put the number one rod through the block. With my luck it would not be the number one cylinder but there have been so many reports of that particular cylinder causing difficulties the odds might be with you. I believe number two is also workable through the small oil pan as well. I agree this is not the absolute best approach but might give you some more time on that engine. You could plastic gauge number two as well to see if it is very worn or damaged if #1 were the problem for example before buying even the bearing shells.