There is a clacking noise that is coming from the front end of my volvo, especially when I accelerate. The mechanics thought it might be the main bearing, but they really couldn't tell. Is that a common problem with this make and model?

Metal shavings and a clacking noise definitely are going to require a full investigation. Its hard for anyone over the internet to tell you anything with confidence on this one. If that mechanic can't tell you for sure whats going on you may want to go to an independent shop that deals specifically with Volvo. Here is a link that can help you find a good shop. Alex https://repairpal.com/repair-shops