headscratcher over E420 problem

[brokebyducati]

Okay - here's the situation - my wife's 97 E420 has had ticking since we got it - assumed it was the usual oiler tube problem and got the parts. We pulled the covers, found a blown tube on each side and replaced all of them. Fastened back up and engine was quiet as could be (and I was happy). Within a week of driving, the covers loosened up a little and the car sat for several days (maybe a little longer) while I tried to get the time to retighten everything. After I retightened, the tick-tick-tick was back! I don't think we put more than 100 miles on the car when it was oiling correctly - any thoughts on what could have happened? The sound is definetely coming from the drivers side bank this time...(mostly passenger side last time)

The car runs great, etc but this ticking thing is out of hand - I'm ready to drive the thing into a train -

Thoughts on what could be the issue now?