[MDairheads] Brakes / Hydraulic hoses. An inquiery

[b_line750 at verizon.net]

  Gentleman, Ladies,

  In recent efforts to sort out nagging brake issues, I have a question.  What causes old rubber brake fluid hoses to stop allowing fluid to return to the master cylinder reservoir upon releasing the brake lever ?  With the caliper and the master cylinder fully reconditioned, and new fluid pumped in, the brake pads only partially retract .  A small parentage of drag or squeeze remains. The wheel refuses to spin freely.  When the old hoses are tossed in the trash and new hoses are installed, compliance is restored.   I don’t get it. 

  With 120psi blasted through the old hose, no obstruction is witnessed.  When the rubber hose is razor knifed into short sections, no crimp, kink or obstruction is obvious.  The ID appears consistent.  The old hose acts like a one-way check-valve.  Pressure is squeezed in, but fails to escape. 

  Any ideas.

   Bill.