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06 powerstroke. Came to stop sign, no brakes. Sometimes I have pedal, other times pedal goes to floor. I suspect its a master cylinder but not sure. The truck doesnt have a brake booster like a car. This is this first ford I owned and just got it about 6 weeks ago. If anyone has advice, I'd greatly appreciate it...
 

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It does have a booster, it just works off of hydraulic pressure rather than vacuum like most other gas vehicles. However, with the pedal going to the floor, I doubt it's a booster problem. It's more likely the master cylinder like you said or possibly the ABS system. Whatever you do, stop driving it until you get it figured out. I assume you've checked the fluid level. Are there any signs of fluid leaking at the wheels? Not sure of the miles on the truck, but this would probably be a good time to go through the whole brake system and flush out the old fluid and know that you have dependable stopping power.
 

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The assist (booster) you have is hydraulic like all diesels since they don't use vacuum for assist like a gas engine.I think you should call a different supplier because unless someone has messed with your truck the parts guys can use your serial number to get you the right one. Also you could buy one here from a Ford dealer but it sounds like your in a hurry.

Randy
 

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Not all diesels have a hydroboost. My 2017 uses a vacuum brake booster. :poke
The vacuum doesn't come from the engine though. I'm not really sure why they chose to go that route. IMO the hydroboost is a better system, especially on these bigger trucks.
 

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Was this problem ever solved? I have the same problem on my 05 after front brake hoses, front brake pads, and driver side caliper. Bled several times and had good brakes then all of a sudden they were gone. One second I had them, the next second they were nonexistent, and the brake warning light came on. Checked fluid, it was low, but not empty. Checked for codes, nothing. I can push the pedal all the way to the floor with ease and make it stop, so it feels like air, but I couldn’t believe it would be air in the system after bleeding 3-4 times all the way around RR LR RF LF.
 

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Air in the ABS pump, you can make a few hard stops on gravel or dirt to activate the ABS system -- or use Forscan to flush the pump -- still will need to bleed the calipers again tho, since the pump will push the air thru the system
 

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And make sure you didn't get the wrong caliper (passenger) for the driver side, because air doesn't like to go down... :D

-jokester
 
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Where is the pump located? I’m sure you’re right on the money because I didn’t know that the ABS system had anything to do with hydraulics. I thought that it was just an electrical signaling to not let the brakes lock up but that makes sense. I will try the hard stop thing, but I wonder if I’ll even be able to hard stop on loose gravel with the brakes not engaging correctly.

I know I got the driver’s side caliper correct because they had a $60 core charge with the mounting bracket. I examined it to make sure it was good to go and it was identical to the one I took off. Autozone rebuilt it but it even had Ford and matching part numbers stamped on it. I have good pressure coming from each bleeder screw, but I bet the ABS pump as hydro said is probably my problem. I will find it, bleed it, and bleed the calipers again and report back. I appreciate the replies.
 

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Autozone doesn't rebuild it, they source it from the cheapest rebuilder they can find. All calipers are going to say Ford on it. Ford contracted TRW to manufacture the calipers and they all have the Ford insignia on them.

The point about the bleeder screw is that the calipers left to right are interchangeable, it's only the bleeder screw location that is different and even some shop mechanics have installed the wrong side caliper, especially when the rebuilder puts the wrong caliper in the box. So it's important to check as an upside-down caliper has the characteristics you are experiencing.

So does air in the ABS controller, which consists of electronically controlled valves, pressure pump, and accumulator. If during a caliper change fluid was allowed to drain out of the master cylinder, air usually gets into the ABS unit. That's a bear to get out without having the computer control to activate the valves, pump, and accumulator. There's no bleeder screw on the ABS unit, which on your truck is located near the master cylinder on the driver's side. It has all the hydraulic lines going to it.


Dexter,

Ford went to all vacuum to try to save money. A vacuum boosted system does not have as high of an assisted hydraulic pressure as the hydro boosted units. I agree, with heavy GVW's I prefer the HB in all situations. Until the power steering pump fails. Nothing like loss of assist in both brakes and steering at the same time.
 

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