It sounds like the need to bench bleed the master cylinder to me.
These things vary in sensitivity to this need but there is a lot of documentation in various shop manuals to recommend that you do this first.
Do it on the car though. Just make up some tubing that curves around back into the reservoir. It only takes a couple of pumps to do it.
I also find that if you use a vacuum pump on the individual wheel bleeders, that helps a lot as well.
Considering how many masters I've damaged trying to pump up the pressure, I use the vacuum pump regularly now as a precaution.
Buy one. They are worth the "investment".
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