They are probably full of junk, just spray some carb clean on them or some oil. If the dealer strips them they will charge you $100 an hour to get the stupid things out. I ruined the head on one of the bolts on the mount under my turbo. But MB thought of this and I was able to get the entire bracket off the engine block rubber mount and all.
A vice and hack saw later and the bolt was out.
Engine mounts are a pita job.