I agree with tangofox. Even if you have new hoses, just disconnect one for a few seconds and reconnect. Badda bime, badda bam, badda boom!

The problem with the evac system is that all the crud in the oil rests at the bottom of the pan; even if it is hot, some crud will always settle at the bottom. This is why the drain plug is located there. Also, a high pressure evac just might pop out a seal.