It would seem to me there are two possible paths to take here. First, find the component in the brake system that is ceased, master cylinder, or slave cylinders and replace them. That's a fairly substantial job. Or you could do what my friend has done with his 580, never go fast enough to need the brakes, or use drag the bucket to get stopped, and never tear into the brakes. His tractor is used daily, and for more than 10 years now the brakes have been ceased. I have looked at fixing those brakes ......... and suggested that he just drag the bucket.