The engine mounts are fluid filled. If there is indication the oil has leaked out, replace the mount/s. Kinda difficult to describe in words but there are longitudinal channels cut into the bottom bowl shape of the mounts just above the crossmember. If there is less than 13mm vertically between these straight sections and the crossmember, the mount has collapsed beyond the point of serviceability. There is a special measurement tool that's easy to make. Simpler still, figure out which of your knuckles is closest to 13mm and slip it between the straight/longitudinal surface of the mount and the crossmember. If it goes through, the mount is fine, if not, replace the mount. The exhaust side mount tends to collapse before the intake side.

Sixto
87 300D