I have an E150 van, but thought I would check with you all. At low speed, like pulling into a parking spot, the brakes get spongey and won't stop! Haven't hit anyone, yet! It almost feels ABS related, like the pedal is high and if you pump it works, but if you jam down you just keep rolling forward.
Any thoughts?

 

Probably the master cylinder going bad.

 

sounds like master cylinder to me also. we had a 99 e 150 at work that master went at 40k. its rare but it happens.

 

it could be the MC... but run some diagnostics before replacing it... If you had a bad seal in the cylinder, you would feel the issue at any speed. The fact that you only get it at low speeds is odd.