What constitutes a bad engine mount?

[roadracer311]

Another data point:
I replaced my engine mount today at 32k miles (went with the 987 mount). When I first removed the old one, I thought it still looked good, but when I put the bolt back into it and flexed it a bit, I could see large cracks.

The installation process was longer and more difficult than I expected. Had to go out and buy a deep 15mm socket. Can't see a way to do the job without one of those.

Results: the clutch chatter when backing into the garage has gone away completely! I also had intermittant clutch chatter when going forward as well. That seems to be gone too.

In both of the close-up photos, I'm flexing the mount with the bolt so you can see the cracks (you can only see the bolt in one of the photos, but it's being used from the other side in the other photo)