My 1999 C 230 K has developed an EVAP system problem. The "check engine" light is on and my OBD 2 code reader says that there is a problem with the EVAP sensor ( which is in the fuel tank ). I don't think this is where the problem is, because there in no pressure or vacuum present in the fuel tank when I take off the fuel cap after a lengthy drive. Is there a hose or such that is prone to leak that could be causing the problem?