I am removing old linoleum (25 yrs old) which was installed over the original hardwood flooring. There are patches where the old adhesive and the backing of the linoleum do not come up and then there were trowel marks of adhesive. I read about using boiling water. I put some old towels on the floor, poured boiling water over them, let them soak awhile and the adhesive just lifted right up with a scraper. There wasn't really any scraping involved. It came up so easy I was amazed. You might try this.