This is not normal operation. A few things to check, and the reasoning for my ideas:
1. Have you already adjusted the shoes? There are 8 adjusters (one for each shoe).
-if the shoe adjusters are backed out, it wall take multiple pumps of the pedal to move enough fluid into the wheel cylinders to properly engage the brakes.
2. Were you extremely careful to ensure that the correct wheel cylinders were installed in the correct locations?
-There are differences between the wheel cylinders, and installing one or more in the incorrect location will result in air that is trapped in the cylinder and impossible to properly bleed.
3. Did you "bench bleed" the master cylinder before connecting all the lines?
-Trapped air can manifest in a few symptoms. Sometimes (usually) it makes it very hard to build pressure and gives the brake pedal a spongy feel. Sometimes, multiple pumps of the pedal will eventually compress the air in the system and allow pressure to build. Upon release, the air can decompress and push brake fluid back to the top of the system.
My recommendation: Check the shoe adjustment, check the part numbers on the brake cylinders to ensure that everything is in the right place, Disconnect the master cylinder and "
bench bleed" it, reconnect the master cylinder and bleed the system until you get 8-10 cycles of bleeding without bubbles. Be redundant and thorough with the bleeding process to ensure you have gotten all the air out.
Hope this helps.
