I use a vac pump to bleed my brakes, when I first started using it I thought, boy this does not work very good because I would always suck air through the connection on the bleed screw. Well I solved this problem by taking the long needle nose type applicator that comes on tubes of gasket maker material and putting it on the end of the bleeder hose. I then remove the bleeder valve and stick the needle nose tip into the bleed hole until it hits bottom and makes a seal. It takes a liitle effort at first but after a few uses the needle nose tip gets worn into the shape of the bleed hole at the bottom and now I do not ever have to press down on it when I am using it.