Ok, so I just purchased a 2001 Ford Excursion 4x4 with 7.3 Powerstoke. The truck has 130,000 miles, an 8" Skyjacker lift, and 35" Toyo AT tires. The truck runs great. Now for the problem. The brakes have been soft since I bought it last month but going from diesel to gas to diesel I remembered there was a difference. Today, I was backing a small, empty single axle trailer down the slope in my yard and when I mashed on the brake pedal it went to the floor. No brakes, runaway truck and trailer........the emergency brake stopped the truck but the trailer jackknifed into my rear quarter panel. So, now the truck only has minimal to no brakes and I have to use the EB to stop. What gives? The dealer that I bought it from had installed new tires, brake pads, all new fluids and filters as he intended to keep it as his DD. But he decided the lift was too much at his age. So the truck has been well maintained.

Last bit of info, no brake fluid anywhere and the MC is at the max line with fluid.

Help!?

 

For me, I'd probably flush the fluid because it's not expensive and then I know I have all the air out and fresh brake fluid in the system, then I'd start pulling wheels and inspecting brakes and brake components.

Stewart

 

Step 1: Don't drive it. If it has to be moved tow it.

Step 2: Do what Stewart wrote.

 

if by dealer you mean used car lot I would assume they used the least expensive parts they could find, those six dollar brake pads they like to throw in there to comply with the "safety" check are junk. steward and mecdac nailed it. dig in and inspect the brake system and refurb it using quality parts.

 

First, thanks for the replies.

Bled the system using the method outlined in a previous post https://www.ford-trucks.com/forums/1223185-flushing-brake-fluid.html. Didn't do the scan tool and not trying to reopen that discussion. What is relevant is that the fluid exiting the bleeder screw had little to no pressure behind it. In some instances it almost trickled out. It had some air in the passenger side rear but as I worked around the air dissipated. Still the lack of pressure exiting the caliper seemed strange. Anyway, the pedal is still going to the floor and returning slowly. The fluid I caught had a greenish tint. So, does this sound like a bigger problem?

 

As Stewart mentioned above get all that fluid out.

 

I really recommend the Harbor Freight vacuum brake bleeder. It's cheap and makes the job quick and easy. One of the best tools from HF IMO. I like to hit the bleeders with a bit of die-electric grease to help prevent air getting back in when I'm working the bleeders. Remember, the brake lines are long on the Ex... I really sucked out a bunch of fluid on the rears to make sure that it was totally flushed out. With the bleeder, it's easy to suck out the reservoir before you start and fill with fresh fluid.

New pads and rotors on my Ex were nice, but doing a flush and bleed made a night and day difference. GL.

 

You probably have a leak/busted line.

Look at all lines for a leak.

The brake pedal doesn't just go to floor for no reason.

 

If you are able to put the pedal to the floor and fluid doesn't shoot out of the bleeder, then something is wrong. If the lines were never opened, there is no way that air can suddenly be the problem. Something broke and it sounds like something inside the master cylinder. Further bleeding is probably just going to be a waste of time.

With all the bleed screws closed and the engine running, what does the pedal feel like? If it goes to the floor then your master cylinder needs replacing.

What brand of tire did he have installed? That will give you an idea of the money he spent on the rest of the parts.

 

The truck sits on a new set of 35x12.50x17 Toyo AT2 Extreme tires.

With all bleeder screws closed and the truck running the pedal will go to the floor with little resistance. The return is slow. The brakes have been "soft" since I got the truck. The lack of brake fluid pressure at the bleeders seemed odd from having bled brakes in the past. There are no visible leaks anywhere. The system is moving very little fluid as I bled brakes for 30 or 40 minutes yesterday and only got 1/3 to 1/2 an empty water bottle full.

 

Something I just thought of. The other day I noticed fluid on the ground. It was from the power steering reservoir. When I checked it, I found the fluid appeared to be coming from the cap. Upon checking it, the fluid level was to the top of the fill neck. Since the "boost" come from the PS pump, could this hint that the hydro has stopped working?

 

This. Read the OP and didn't think this had anything to do with air in the lines. They can be $6 pads or $60 pads and it wouldn't matter for this, cheap pads can't cause the pedal to go to the floor.

If it was better before and suddenly got worse. something failed. If there's no fluid leak the problem is in the master cylinder. Sounds like your seals let go.

 

In your experience, should the Hydroboost be replaced as well or are they less likely to fail? Again, I have no brakes which leads me to believe the "emergency" braking built into the HB has been exhausted. Thoughts??

 

Hydro boost is a assist. If it fails pedal pressure would need to go up to compensate.

If your brake fluid level does not change after several repeated brake cycles it's master cylinder.

If brake fluid level in resivor decreases after repeated braking cycles you have a leak.

Or your linkage from brake pedal to HB unit has broken. But I doubt that is issue. I am betting you have a busted line. To "soft" brakes say weeping line or rubber line that is ballooning. Than complete failure says weeping line broke or ballooning line burst.

 

I agree with Rock. A failure in power assist would cause the brake pedal to become hard to push, but it wouldn't go to the floor. If it's going to the floor and you're not losing fluid you need a master cylinder. Not an expensive part to replace, unfortunately your rear quarter panel probably isn't that way.