JD 5400 brake problem

[Brokenheart]

Working on my brothers 5400 with no brakes. If you pump the pedals they will pump up. I removed the brake valve and connected each brake line with a porta power and pumped them up to 100 psi and they both held pressure for 15 minutes. I had the rear end jacked up and the brakes held. Naturally I thought the valve was bad so we replaced it. After bleeding the brakes the problem still exists.
TIA for any suggestions

 

[beenthere]

Hope this gets added as an update onto your other thread "5400 brake issue" from 2 months ago...