Ford Windstar ABS help

Having an ongoing brake problem with my 1995 Ford Windstar brakes. Symptoms of the problem are a noise, like a twang, intermittently when the brakes are depressed along with a binding feel to the pedal
action. It goes away after a few presses of the pedal. Brake action still occurs during the failure but it is not firm braking pressure. After a couple of pumps the problem goes away. Local garage looked at it and couldn't find the problem. Diagnosing it myself, front pads and rear shoes still have plenty of surface. Replaced both rear wheel cylinders and all new springs in the rear brakes. Last weekend took apart the brake pedal and no problem there. Replaced the master cylinder, still no help. Front calipers appear OK but I was about to change them anyway to see if it fixes the bug, but tried something first. To debug, I removed the ABS fuse from the fuse block and re-tested. Instrument panel lights come on, this was expected, and on hard stops the brakes are not as firm, but disabling the ABS appears to have solved the twang noise and binding. I am going to leave the fuse out for another few test rides but this seems to make the problem go away. I have no experience with ABS systems but I am wondering if I can do some more simple debugging on the sensors or on the system to narrow the problem further. Local Ford dealer is generally a ripoff artist and I don't have any other ambitous mechanics locally that want to spend the time on this problem. Any help on diagnosing ABS problems would be helpful. Obviously I would like to start with the wheeel sensors since I know the ABS unit is probably not a cheap item...
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Hi, I have recently had a somewhat similar problem with my '95 Windstar. The sound I was getting was from an activation of the ABS system upon normal dry weather braking. After replacing the rear wheel speed sensors, cleaning the front wheel speed sensors, replacing a suspect front caliper, etc., a closer examination of the front wheel speed sensor rings revealed a fine crack in each one. The rings could be individually replaced instead of replacing the entire hub assembly as some suggest. The parts were $25 each if I remember right. Good luck. Rich

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