However, the dust must pass over the sliding surfaces and often becomes 'embedded' or 'stuck' to those surfaces. Over time, this build-up will scratch the block, leading to a minor leak. Regular cleaning by a qualified technician can greatly reduce the possibility of this problem but the owner can also clean off dust build-up. Simply blowing off the dust is usually enough but using a feather duster also does a great job. The least common problem is cracking.
Cracks can develop in any piece of wood.
Repairing the cracks in an air-motor should generally be left to a qualified technician especially if they are present in the sliding valve surface. Cracks around the vacuum supply fitting and the air-motor mounting hardware can be filled with almost any type of filler, but it's unlikely that those cracks are responsible for poor motor operation. Slosh it around for a minute or so and then pour out the excess and let it dry for 24 hours. It's best to remove the tape about twenty minutes after you pour out the excess to aid the drying process. Also, be sure to clean around the holes in case any of the sealer gets under the tape.