Today i was putting on a new caliper and caliper bracket. I read my Haynes manual, and bled the brakes as it said. But after i was finished i have absoultely no brake pressure. So i bled it another 4 times. and i still have no pressure. So i called a mechanic and he said that since i have an ABS system on my car it has to be professionally bled using a bleeding machine. is this true?