I have a 2006 Explorer that is driving me crazy for over a year, and hope someone can tell me what is going on. This is a low mile (50K) that’s been in my family since new, and is used during the winter only so it sits for 6 months a year. The problem is a brake pedal that goes to the almost to the floor and won’t pump up. I’ve looked at every thread that I can find, and tried many things without success. I’ve worked on cars for over 50 years, so it’s not my first rodeo. Remedy attempts have included replacing the master cylinder, front calipers, front brake hoses, slide pins and trips to the local Ford dealer as well as a local independent shop (which now makes a total of less than ten times I have resorted to paying someone else to service my vehicles in those 50 years.

Here are the symptoms, and why only the front has been addressed. The pedal in the car has never been what I would call good and always seemed low and not really firm. It has gotten worse with time. It will stop the car, but no longer will engage the abs on dry pavement. I’ve run enough brake fluid thru it to fill a small pool. If I isolate the front calipers, the pedal is immediately rock hard and high. All the other part replacements have had no effect. When the car is off, the pedal is initially low, then as the vacuum reserve is bled off, the pedal gets higher (to about half), AND can be pumped up, but when the car is started, it immediately reverts to just off the floor, and it spongy enough to bottom out when pressed hard. I also can say that the pistons in the front calipers visibly retract after the pedal is released after being depressed. So each time the brakes are used, the first part of the travel is used to take up the slack in the calipers. I thought perhaps the rotors were flexing or the caliper was binding, so I took the calipers off the rotors and put a solid metal spacer in between the pads, and they continued to retract upon release. Finally, someone suggested installing a residual pressure valve for discs (2psi) in the line and I was convinced that this would solve the problem. So I now have one in the line between the MC and the ABS module (off the back chamber). No change! Needless to say, my frustration level is very high, but I hope the piston retraction issue will trigger an AHA moment for someone.

Thanks for listening.

 

Have you tried adjusting the brake booster push rod? If not, here's a pretty good video on it.

 

Problem Solved, yes it took years!



After tearing my hair out, I had given up on solving this issue, and just driving the darn thing with a VERY low brake pedal. But I hadn't stopped telling my story to everyone I ran across with a mechanical bent. Then in the summer of 2021 I was bending the ear of a guy at a drag strip and he said "I know what you need to fix it" and took me over to his highly modified International truck. Pointed to his master cylinder and the two valves on the out lines. Residual pressure check valves. Used mostly on street rods that have low mounted master cylinders to prevent back flow into the MC. The key was that the pistons on the front actually retracted after the brakes were released.



Normally the suggested valves are 10psi for drum brakes, and 2 psi for discs. I tried the 2 psi, both at the caliper and at the MC...nope, found some 4 psi...nope, and finally tried a 10psi in between the MC and the ABS unit on the front brakes only. Miracle of miracles, I now have a normal pedal, brakes don't hang up and the pedal is firm. Did the fix in 2021, Pedal was great thru winter of 2021, sat during the summer and again good in 2022.



I believe the whole fiasco is due to Ford having the front calipers retract a little bit by design to improve gas mileage, and just got a bad set of tolerances in this explorer.

 

Perseverance pays off. Well done.

 

Saving this thread, might come in handy for me later on