I have a 2004 E350 with the 5.4L v8. Recently I noticed the brake pedal was becoming soft. By that I mean if I'm sitting at a light the pedal would slowly go to the floor. My mechanic said it was the master cylinder which he replaced. However, the problem was not solved. He now want to replace the ABS Hydraulic Control Unit, which would cost $800 not including labor. Is there a simpler (ie cheaper) fix? Is there some trick to bleeding the brakes? Many thanks,
Larry

 

Something I would suggest is make sure there are no leaks in the system. Check at all the wheels and then under the vehicle. A rusted brake line with a hole in it can give the same symptoms. As far as a quick fix , none that I know of. Sometimes clamping off the front or rear brake hoses will help isolate which area is losing pressure.

 

Hey Hanky,
Thanks for the reply. The mechanic said they manually bled the brakes 5 times. I haven't asked him about a leak, but I'm thinking they would have noticed one after all that bleeding. I'll have to ask.

Is it possible there's still air trapped in the ABS Hydraulic CU or somewhere else?

Thanks again,
Larry

 

Usually air trapped in the system will give a spongy pedal. Pedal going to the floor indicates a loss of pressure someplace and not usually in the ABS unit.
There have been occasions where replacement master cylinders have been defective right out of the box.

Will the pedal hold position when depressed without the motor running?