So a few week back I noticed my brakes were getting soft. Soft meaning that when braking for any distance, I would hear a kind of "pressure release, squeaking" sound coming from the pedal, and the pedal would sometimes go to the floor and the ABS would kick in. Let me tell ya, its a pretty crappy feeling when your brakes aren't doing what their supposed to! So, I replaced the pads all the way around, replaced the master cylinder (bench primed). I took it out for a drive, and it did the same thing. So thinking maybe the fluid is bad, I flushed new fluid through the lines. Took it for a drive, and it felt good right away, the pedal firmed up a bit, and then it did did it again.

Just so I give as much info as possible, the rotors are looking pretty rough and going to be replaced soon.

So, my question[s] are; What is the next step in identifying the problem? Is there a chance the new master cylinder is bad? Could worn rotors cause the calliper to max out and not apply enough pressure? Even though the callipers seemed fine while replacing the pads, could one or more be bad? If so, how do I know?

Thanks in advance for any help! I read this forum quite a bit, I only post when I have questions, no sense in clogging the forum with my backyard mechanic wrong answers, but I do appreciate the pros that put in their time!

 

Is this truck a gas engine or diesel? The brake systems are different.

 

Its the 5.4 gas.

 

Proportioning valve?

 

Are you sure no fluid is leaking? Maybe inspect for a leak first, especially in the rear lines...

 

No fluid is leaking. The reservoir is full and maintained the same level and there is no signs of drips or anything on the wheels or caliper.

 

Is there a way to test it? Or is it something to replace and see if it was the culprit?

 

Don't know, I'm not a Ford tech. I had to have one replaced on my '88 F250 that was doing sort of the same thing. Funky pedal, eating pads, ect.

 

Front flex lines good shape? they go bad. If so, I could imagine a caliper is blowing internally giving this effect, but it would have happened before (do more searches / wait for a suggestion).

 

Is it possible for a caliper to bypass internally? Or if a sticky piston doesn't apply would the fluid need to be pushed into the other piston causing a mushy feel?

I'm curious

 

The flex lines appear to be in good shape. I was wondering too if its possible that they if they went bad, they could "flex" and absorb the pressure that should go to the calliper piston. Again, I'm just spitballing, because I don't know...

 

I just put a master cyl on a ranger for a similar complaint . Peddle would go to the floor at stops . I had to put on another 3 weeks later ! The reman failed ! This time I went with a new one .

 

Along with knowing is gas or diesel (already answered) there are a few more important questions. Is the vehicle RABS (rear only ABS) or 4 wheel ABS? I believe back in '00 it still could be either. Another question is that before/after replacing the M/C when the problem occurs did you always feel the ABS kick in, the shudder in the brake pedal?

This does not sound like a caliper / rotor / pad issue.

 

The ABS is rear only. Yes, I felt the pedal sink and the ABS kick in before changing both of them (pads/ master). This is why I replaced the master cylinder to begin with.

I'm going to the parts store this morning and hopefully they will exchange the master for me. I think that's the best place to start. It seems like the most likely of the variables.

Thanks for all of the replies, keep 'em coming, and I'll keep the thread updated with how it goes. It will be a couple of days before I get into it, probably Thursday.

 

Also make sure you bleed all four corners well. It sounds like you still have air in the lines..