Be really sure it's the ABS unit that's leaking first. When the brake pedal faded on our 2001 F53 while underway, when I stopped and looked underneath where the drips were coming from, they were running right off the ABS unit. I was able to limp the coach home, and then I began researching replacement ABS units. The price on those things is downright scary! After a couple days though, I added some fresh fluid and stepped on the brake pedal a few times, and then crawled under the coach to check on the drip location. I was thrilled to find that the leak was actually coming from a pinhole in the front brake line from the master cylinder to the ABS unit. A wiring harness cover had worn a small spot through the coating on the brake line, allowing it to rust through, and while under way it was running back to the frame mounted ABS unit before dripping off. Some universal pre-made brake lines and brake fluid from NAPA and an hours work later, along with a complete brake fluid flush and fill that was overdue, and the brakes were good as new. As I said, be really sure...
I should add that if it is the ABS unit, the replacement requires a specialized scanner that's capable of cycling the ABS ports to properly bleed it. Probably best left to a Ford dealer or other knowledgeable repair shop.
Dutch
2001 GBM Landau 34' Class A
F53 chassis, Triton V10, TST TPMS
Bigfoot Automatic Leveling System
2011 Toyota RAV4 4WD/Remco pump
ReadyBrute Elite tow bar/Blue Ox baseplate