Brakelines and lever pressure

[RSRBOB]

I am passing this tip along for general interest. It is a trick we use when
diagnosing hydraulic brake problems. If you want to find out if your master
cylinder is working properly, try this. Take a pair of needle nose pliers,
and wrap the brake hose, (RUBBER lines only!!!!!!!) with a heavy rag. Squeeze
the pliers on the rag, closing the hose off. Now, grab the brake lever or
press the pedal. It the lever still feels spongy the MC is either bad or you
have air between the pliers and the MC