I have a 1999 F-150 ext cab 4x4, I have had a low spongy brake pedal for years. After replacing every brake component, master cyl twice, power brake booster, abs module, soft brake lines, calipers all around, rotars, pads, brake pedal, bleeding until I was blue in the face and many trips to the dealer and other brake shops regarding abs scan tool bleeding which is a crock of @#$% on this truck over the last couple of years, reading all kinds of posts of people going through the samething and also the post that says adjust the push rod between the master cyl and power brake booster ( DO NOT ADJUST THIS ROD IT IS NOT THE PROBLEM ) The rod from the brake pedal to the power brake booster is ''ADJUSTABLE" and is the problem for a spongy low brake pedal. While I was replacing the pedal brake light switch I noticed that the rod turns either way, to the left lengthens it and to right shortens it. The rod has very fine threads and take many turns for a minor adjustment, 30 turns to lengthen it for me which was about 1/2 an inch. Now I have 1/4 inch play with a good firm pedal and brakes that will stop on a dime inside your pocket. I am not saying that this is a cure for everones spongy low brake pedal but worked for me.
man if this worked for your truck, then im gunna pray it works for me. because ive replaced every dang thing that deals with brakes and they still go in 1/2 inch before they catch. but the brakes work fine i just want that tight pedal that makes me feel secure
Just be careful when you make the adjustment, if you go to far your brakes will drag. I adjusted 5 turns at a time, while i was under the dash i started the truck and pushed the pedal by hand for the right feel. Just keep track of how many turns you go incase this does not work for you. I also noticed that I do not have that light whislting sound anymore.
If you crawl under the dash where your brake pedal is and look up, you will see the the rod attached to the brake pedal. Carefully remove the cotter pin and slide off the rod and brake light switch,carefully remove the brake light switch from the rod and move it off to the side. there is also a plastic bushing that sits inside the rod hole remove it as well, that rod is adjustable by turning it. Make sure you keep track of turns or make a mark on the rod flush where it meets the booster. Turning to your left will extend the rod and to your right will shorten it. Like I said before, I did 5 turns at a time then connected it back up and while I was under there I reach up and started the truck and pushed on the pedal for the right feel. I turned it out 30 turns in total and the pedal was good and tight, i then took it out for a test drive and my brakes were draging a bit so I turned it in 3 turns and now have a good tight brake pedal and braking power is a lot better. I dont think this is a fix for all spongy brake pedals but worked for me. I will try to post some pics.