ISTM that you still have air in the system. ("pumping them up" is a clue) With the MC under the floor, I found it really difficult to get all the air out. I had to bleed the system about 4 times before I got it right. The pedal would seem OK and I drove it for many miles without issue. Then the pedal went to the floor when backing out of a parking stall with the steering fully cranked over. Or the pedal would drop on an extremely steep driveway, just when you really need the brakes.
