Issue bleeding brakes
 

I am hoping someone can help me with this one. My car was sitting for the past 13 years and I have been working on restoring it. Over the weekend I rebuilt the front and rear calibers and replaced the flexible brake lines. I went to bleed the brakes and was able to bleed the rear ones with no issue. When it came to the front I am having issues bleeding them. I used a vacuum pump and was able to pull fluid through the lines, however when i try to manually bleed the brakes I have a very slow trickle of fluid from the bleeder valve. I blew air into the caliber and confirmed the pistons move (brake activated). Is there a specific procedure for the fronts? Has anyone had an issue with the proportioning value or the brake master where they have seen something like this happen? Thanks

I've never had any issues with the proportioning valve. It might be that your master cylinder is bad after sitting all those years. Once all the brake lines are open to air, sometimes it can take a long time to bleed all that air out.

I'd say the master is the most likely culprit also.
Being much smaller, the rear calipers require less pressure to move fluid and might seem OK with a master that's bypassing internally.
Besides, with all the other new parts and rebuilding, it only makes sense to do the master as well.