Have them put dye in it before they tear it down. That seal is very good, and usually does not leak unless damaged on install. I saw one last year that leaked from new, and it was leaking out one of the unused bolt holes under the rear seal retainer. When they tapped the hole at the plant, they went a little deep and broke through into the crankcase. Had to put a short block in it. If it was mine, I would have put a bolt in it with thread sealer and called it a day.