I'm a meteorologist and definitely not a mechanic, but thought I would pass this along. The take away is "don't underestimate how loud and clunky a broken passenger side motor mount can be on a S40". Loud clunks and rattles (especially over bumps) started coming from the front passenger side of my 2004.5 S40 a while back and trouble shooting was like chasing a ghost. I had the front end inspected by several shops (including the dealer), the front axels replaced, and the front passenger side control arm replaced...no luck. One shop even tested the front passenger side motor mount, but the usual tests of trying to pry it or brake while revving the engine (and look for engine movement) showed nothing. I finally asked one shop to pull the passenger engine mount and visually inspect it...sure enough, it was cracked. $250 and a new passenger motor mount later, my S40 sounds great again. I hope someone out there finds this helpful.

 

Thank you for posting your experience. My 2005 did the same thing, cracked completely in two. You cannot see it either. And you are the 2nd one to have this issue lately.