Teflon Seal Prob

Dear All,

We have Injection Molding machine Its tonnage drop problem facing so we remove tie bar & check Teflon Seal. Some seal found damage so we remove old & try to insert new. but they are entry in there position. In factory manual they mention just heat seal in oil near 150 degree cel. so we do that than our seal expand & also enter in there positing but after cooled seal does not contrast in original position. so seal is loose fitted. still our work is stop any body suggest me that our procedure is right or wrong or any other way to inserting teflon seal