big problem with brakes on 05

[Simoncx]

My 05 f-350 has been having a werid problem, when I start it up and everything is fine. I drive 100 ft and press the brake pedal the brakes feel like they get soft and then get stiff making a whining noise, feels like the brakes aren't grabbing. Then the abs light comes on and they work fine again??? I looked over everything and everything is good, could it be the hydroboost or mastercylinder? Anyone have a idea what it could be?

[papaschoo2010]

sounds more like an abs problem possible speed sensor issue need to check for abs codes first.

[mcflan]

Wheel bearings. Wheel bearings will throw the ABS light on. Is it on both sides?

[Simoncx]

I'll try to scan it tomorrow to see what codes come up. Never really considered wheel bearings, hopefully it just a abs sensor.