We have a 1981 Fiat Spider 124 2000. And just replaced the master cylinder, brake booster, caliper seals, rotors and pads and got done and started the process of bleeding. We finished and started on the front and discovered the front lines have no fluid flow or visible leaks. We are confused and cannot find a way to get fluid to flow.

I normally start with the rears as they are the farthest away. Did you prime your MC. Try cracking the brakeline fitting at the MC and pumping until you get fluid out. I also had to fill my calipers to get the bleeding process going.

Be sure fluid is getting to the master cylinder.

I use a inexpensive vacuum bleeder but find that the spider gravity bleeds well as long as you prime the master cylinder first. Note that the rear axle needs to be on jack stands to open the proportioning valve if its still part of the system or you will not be able to bleed the rears.