Still the same problems with brakes. I bought this truck in Nov of 2017 a 2011 F-250 Super Duty Super Cab XL 4WD 6.2L flex fuel gas engine, and the brakes are still the same only worse. Here is the problem. When I first press the brakes to stop the brake pedal goes to withing a couple of inches to the floor. Sometimes when I start the engine and go to backup when I press the brake pedal it goes down to within a inch of the floor and my foot hits the gas pedal because the brake pedal sinks down to far before the brakes grab hold. Hope I am explaining this correctly.

Here is what has been done so far. I’ve had the truck into 3 different Ford Dealership Garages. Here is what they did.
Replaced the pads and turned all 4 rotors.
Brakes Have been bleed 3 times. (which seemed to help for awhile).
Was told I needed a new Brake Booster. That is BS. The brake booster would not let the pedal go almost to the floor unless the pin rod to the master cylinder was way out of adjustment). I can see where the garage that told me I needed a new Brake Booster had taken the master cylinder loose from the brake booster when they were supposedly checking it.
The Last ford dealership I went to, road tested and said the brakes were OK and acting Normal. The pedal should not go down that far before you have solid brake pedal. I have owned several ford including 3 Super Duty and never had this problem before.

Yesterday I was coming to a stop at a stop sign and the brake pedal went to within one inch of the floor. I pressed even harder and the pedal sank clear to the floor. I managed to drive the 2 blocks to home and I had brakes as usual put did not put a lot of pressure on the pedal only enough to stop. I ordered a new Master cylinder which will be here on Wednesday and also purchased a Bench master cylinder bleeder kit to bench bleed the new master cylinder. I just can’t believe that I need a new brake booster. I will try the new master cylinder and if that does not correct the problem then I will buy a new brake booster.
Any advise or thoughts would be appreciated.
Mel

 

Booster isn't the problem unless something on the diaphragm is collapsing a couple of inches and I doubt that. I would have been guessing the master cylinder long ago. Make sure there is no gap between push rod and master cyl piston. I haven't had the displeasure to work on one yet so I don't know if there can be any adjustment of brake rods.

 

 

 

I have already ordered the master cylinder and a Master cylinder brake bleeder kit. I am thinking about bleeding the brakes using a mityvac vacuum brake bleeder. I have always used Speed bleeders in the past. starting at the farthest bleeder from the master cylinder. RR, LR, RF, LF, From what I have read it appears most start at the LF closest to the master cylinder using a vacuum bleeder. What do you use and how do you bleed the ABS?
Mel

 

I would replace the flex hoses.

 

Why would I want to replace the flex hoses? They are not leaking and are not soft or bulging. The master cylinder stays full and the brake fluid level in not low leading me to believe that the Master Cylinder is leaking past the piston internally or there is air trapped in the system somewhere maybe the ABS because there has been air in the system before. That is why I'm thinking of using a vacuum bleeder. never used one before.
Mel

 

Pads and rotors won't cause an issue like that. Neither will a booster, failed it would be a hard pedal. . Hoses won't have that displacement for what you're describing..

The two most likely issues are either the master cylinder bypassing, or the ABS controller is bypassing internally.

The ABS controller does three things. It either dumps fluid into the internal accumulator to relieve pressure, the pump activates to apply pressure, or the valving dumps some fluid into the accumulator to lower pressure and then prevents additional fluid down stream. That last one is called dynamic proportioning.

Considering all the bad professional advice you've gotten so far, changing the M/C on your own is also the first step I'd go if it was my truck. If that doesn't work then it's most likely the ABS controller. I don't have the service manual for your model year, but the earlier Superdutys had an easy check for the ABS bypassing internally. There was a port on top and all you had to do was pop the plug and stick a wire down the hole to see if there was movement. Probably not the same on yours, but I'll include the procedure for the earlier trucks.

Also all booster rods have an adjustment, but once they are adjusted at the factory they should not need to be adjusted again unless the master cylinder manufacturer did not machine the piston depth correctly. There always should be slight clearance between the pushrod and the M/C piston.







Pretty much how we did them in the vehicle test garage.

 

FWIW I have a vacuum bleeder and it only leaves the shelf when I don't have anyone around the shop I can snag for a few minutes. Even then I will get a assistant to press the pedal to bleed any air left in the top of the cylinders/calipers. The biggest problem with vacuum is air getting around the threads of the bleeder valve and not getting a clean bleed. Also when that happens it will draw air right back into the system if you remove vacuum before closing the valve.

Unless your pedal will pump up I doubt it's air in your system. I agree with too many toys. Master first then look at abs system.

 

Ford doesnt adjust the booster rod at all from the factory FYI. There are numerous threads in the f150 , super duty, and even e series Van's having poor pressure/low pedal on this site. And every time it's a rod adjustment that cures the problem

 

 

UPDATE Replaced the master cylinder with the new one after bench bleeding it. I then used a vacuum bleeder and then followed up using the two man method. Got all of the air out and have a hard pedal, but there is still to much travel before I get a hard pedal. I looked at maybe adjusting the push rod on the Vacuum booster, but the rod is recessed in the booster it does not stick out like the picture shows. I can get a 7MM socket on the tip of the rod, but no way to hold the rod to adjust it. Is there a special tool for this or do I have the motor running will the rod come out far enough to hold it while Adjusting the head with a socket. Hope someone can help.
Mel

 

Did you have someone press the brake pedal and then try to get to the rod? Does it stick out far enough when the brake pedal is pressed?

Edit to add: A picture of the setup would be helpful.

 

No I didn't. I read somewhere not to press the brake pedal with the master cylinder removed. I also read something about running the motor with the master cylinder removed. I would think that there would be a vacuum leak if I did that and the motor would act up. I need someone to chime in that has done this before and to explain how they did it.
Mel

 

OK, again a picture would be helpful. To start with if you look at your master the piston should be flush with the end of the cylinder minus the snap ring that retains it. There should be a shoulder on the master of about 1/2 inch or so to fit into the booster. Measure the distance from the tip of the rod to the opening on the booster and then measure the distance from the bolt boss on the master to the end of the piston. It should be the same.

FWIW, the booster should be hydraulic and starting the truck without the master on will not harm anything. Have you tried to press the pedal with everything installed and checking for end play? That much play should be pretty obvious.