I had pulsing and "spongey" brakes a month ago on my '00 150 4X4. I replaced the ABS sensor, and it didn't help. I then realized that my front wheel hubs where SHOT. I replaced both front hubs, flushed the brake system. And all my issues are completely resolved. To check if your wheel hubs are bad, get one tire completely off the ground. And then try to move the tire up and down (without moving the suspension). You can do this by grabbing the tire on the bottom and pull to you. IF the tire, wheel, rotor, etc moves but suspension doesn't then you need new wheel hubs. Chances are, if one is gone the other ones won't be very far behind it. I would also have your ABS sensors checked. If one is out you need to replace that sensor, and this could be where all your issues are coming from. Hope this helps.
Just as an FYI, what happens when your hub goes out, the metal shavings will destroy the ABS sensor which will cause your brakes to pulse when trying to stop. And IF you hear some strange noise coming from the front end, and you are sure it is not coming from the engine. Chances are that your hub is shot.
Last edited by Da Wolf; 04-14-2010 at 11:48 AM.