So I recently bought a 99 4.0 (it has ABS) when I bought it the breaks were already spongy. I’ve replaced the discs and drums all around, the wheel cylinders, and the master cylinder. There’s no leaks and when I bleed the breaks they get stiff but as soon as I turn the truck on they get spongy again. What are some recommendations on what the next steps should be?

 

Find a dirt or loose gravel road. You want to activate the ABS. So about 10-15 MPH apply hard BRAKE to get the wheels to lock up, this will get the ABS system pumping and hopefully get any air out of the lines.