Can't keep air out of system

Where did you get the master? I seem to recall something about a bad batch that Wilkinson had made up.

Julian

No, this is not one of those. I recall those would disintegrate by turning the fluid black. This is Pantera Performace. Is original.

Are you using DOT 5?
If so you will have a very difficult time.
Flush and switch to DOT 3 or 4.

If you not holding a good vacuum with the MityVac when you open the bleed valve or sucking much fluid, you may have a leak at a joint. Try bleeding the tradition 2 person way and see how you get on. Work the clutch pedal a number of times and check for any leaks.

I am using DOT 3-4. I guess I'll just keep trying, but seems futile at his point. I really think the NEW master is bad, possibly leaking past the seals, but not externally, not sure this is possible, but is the only thing I can think of.

Change your bleeder valves. Sometimes the seat on them gets compromised when they haven't been operated in a while. Could be as little as a year.

Ironically the bleeder valve will let in air but doesn't necessarily allow fluid to escape.

RRS1; Your hydraulic question: Yes you can have air introduced into a supposedly closed system; however, air has to be introduced by a vacuum created by a low pressure area in the system. Typically, where you are creating pressure in your lines, should you have a leak (split line, cross fitted fitting, etc.), you normally would see leakage. However, in the master, as well as the slave cylinder, when the pistons are moving back and forth, you may be getting "blow by" past one of the
O-rings that are fitted on the pistons in the master or slave, or you still have a pocket of air that has yet to be purged from the system. Since your system is new and after pumping the clutch pedal and getting decent pressure, are bubbles returning to the resevoir? Is the red tube clear enough to detect air in the tube? As with bleeding brakes, I have run a tube from a bleeder valve all the way back to the master and pumped the brake pedal to purge the system of air. I agree with the previous post, the Mighty Vac and speed bleeder may not be purging the air out. (Getting the air out of a new system is like draining the water pipes in your house and turning the water back on - a week later the shower spigot all of a sudden decides to spit air because the air in the pipes finally made its way to the open spigot)

Appreciate the responses. I've thought of running the tube from the master all the back to the slave and will try that next. Will also investigate the two valves I have used.

Well the problem turned out to be air leaking around where the red tube connects to the slave fitting. What made it difficult to detect was there was never any fluid leaking during the bleeding process. I finally did get enough air out for a test drive and after repeated clutching under pressure, the fitting decided to let go on the highway. NO GEARS, and pedal to the floor. I coasted to an off ramp knowing that as soon as I stopped I was done. Tow truck charges later, I ordered a braided stainless line. RATS! there goes my stock look.