inrebuilding the engine we can't get the rear engine seal to stay in place. we put in a thicker seal and it ran for 45 minutes before blowing out last night.
rear engine seal won't stick on 2001 Subaru Legacy
Are you using a factory seal? I would use the VIN number and go to the dealer and get the exact seal. Don't use any grease or sealant on the seal, install it dry after cleaning the area with brake clean to remove any oil, so it does not slip out again. I have worked on lots of Subaru 2.5 liter engines and they have updated Cranks Shaft seals, because they have had problems with them slipping out an leaking a lot of oil.
If indeed the seal is blowing out of it's bore then a factory seal is in order. But during install you should use high temp RTV on outside contact surface and let it set up overnight. And most important is to use vasoline petroleum jelly on the inside of contact surface to prevent seal from rolling or tearing the sealing lip. Also make sure seal is in all the way and not just flush with the outer contact surface, you may need to use a blunt ended punch (NOT A SCREWDRIVER) to accomplish this.