BRAKE PROBLEMS XSARA PICASSO

Hello everyone, I'm new here, but I hope to catch up as soon as possible. And this said, to see if someone could tell me why sometimes when I brake with my Xsara Picasso HDI. 2.0 The pedal goes to the bottom and I have to quickly release and step hard again. They checked and purged the circuit twice, the drums tense me, they changed albums and front pills, but still there is no way. They told me that they were already going out of hand and that they could no longer help me, that it was to the official service. And as you can all understand, there are not the times to pay a money, being that here someone could help me. Thank you very much in advance.

This type of problem in particular is more common than the problem of the brake pump, such as a double -effect cylinder with some rates inside that are rubber that are responsible for pushing the cylinder sometimes they are scratch internally or the rubber deteriorates this is presented as a blast Pedal goes down and you must pump it, but everything indicates problems with the lucky bomb and let us go.

Hello friend, as the fellow Kikemec explains the fault comes from the brake pump, repair or change it as soon as possible for your safety and that of the other conductors, greetings.