Hello,
I doubt the line is doing much to begin with...........all the cars I have worked on have had to clear it out with a stiff wire and sometimes replace it as the crud is set like concrete inside the small diameter steel tube.
When I replaced the waterpump on my M115 gas engine, I forgot to clear the vent line and had to top up the radiator every other morning as the coolant level kept dropping slowly. Could not find any leak, then remembered I had not cleaned out the little ba$t@rd.
The REAL bypass line is the water hose between the thermostat housing and the waterpump housing.
Hope that helps.

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Nachi11744