Master Cylinder -suck and blow?

While trying to bleed my brakes, I'm noticing that the hose appears to be sucking air in as well as pushing fluid out. Kind of evening out, but leaning towards more air going in than fluid coming out.

I disconnected the MC and put my hand over the bore, and pushed the plunger. I'm definitely feeling air being pushed out, but I'm feeling a tiny bit of air being sucked back in past my hand. Should it work this way?

 

To clarify- I just rebuilt the MC. And I bled the lines afterwards the first time with no problem.

 

Yes....the master cylinder has to let a small amount of brake fluid back into the reservoir when you release the break handle. This action allows the brake pads to release a small amount.

Kenneth

 

the purpose of this is to release the pressure in the line. If it only pumped fluid in then your brakes would be permanently engaged.
THAT situation happens all the time when MC's get cruddy or misassembled.

 

I found with mine I had to pull the lever incredibly slow and all the way, to pump up the system, then hold the lever in when you crack the bleeder. Do you have a vaccuum tool, that can help speed the process, but not necessary.