ME TOO! I had soft baked pedal, I paid to get them looked at, I was told they bled them, put new pads and rotors on front, but the sliders that locate the front pads had wear marks where repeated use has left notches on spindle. These were welded then ground down to be flat so the pads weren't hanging up anymore (The pads were replaced because they were worn off more on one end more than the other). the job cost me 485$. but the brakes are still soft, now they say I should get them to change the booster another 100$ plaus their labour (another 100$) with no promises this will help. I said I'd pay for the booster but they can eat the labour if it doesn't fix the problem with the soft brakes, they said good-bye. (Good thing I put my shorts on backwards that day)now what I think perhaps it may have soemthing to do with the antilock brakes, the light doesn't come on when I start the truck, nor has it ever come on. There is no wiring for the relay under the hood (1994 5.2 litre, 4x4 Dakota SLT.) I have checked the hoses all apear to be in good shape, rear brakes were set up to drag just slightly, what the hell else can I look at???
FLICKER needs help please and thanks.

 

Soft pedal is one of two things, air in the lines, or mis-adjusted rears. (rears control pedal height as well.)

Air in the lines may be from a poor bleeding job after having the system open, or, from a leak in the system. The line going to the rear brakes is notorious for rusting out, and springin' leaks...... which are not always obvious. May also be an internal failure in the M/C.

A bad booster will give you very little braking power for a LOT of pedal effort.

Are you losing any fluid?
Does the pedal go down further than you think it should before anything starts to happen?

 

If I pump mine, I get about half the stroke on the second push, and nearly half of that on the third...and i can stand on the pedal and it does not sink.


Gotta be air, swelling in lines, or MC piston seals leaking by.

 

Or rear brake adjustment.

 

....OR rear brake adjustment.....and having one ton cylinders is not an issue, as I have changed mine.

 

Supposedly you can put her in reverse and then SLAM on the brakes a few times and the rear's will adjust....

 

Does that work for our trucks?
i know it works for older models

 

Supposedly. I wouldn't hold my breathe though....

 

With engine Off, does the pedal feel soft or hard after a few pump? if it is still soft, you got a problem. If it turns hard, you should be OK.
If you alrdy bleed it, then it can't be air. As some mentioned, it could be your rear drum brake. Take off drum and inspect, sometimes Spring or the Shoe falls off because it is too old.

It could also be low quality brake pad that you use too.
If you want to isolate the problem, simple Pinch off your flexible brake hose one at a time, see which one you pinch off give you a solid pedal. also try to Punch Both front, or Both Rear to isolate the system.
I doubt it could be the booster. The Booster is nothing but an Air assist unit, if it fails, you get no assist, not a soft pedal.

If you Pinch ALL 4 Brake lines, and it still sinks to the floor, you probably need a master cylinder.

 

Just don't mash on the brake pedal with the rear drum off! Long time ago way before I had a clue I took the passenger rear drum off my S10 Blazer (can't remember why) and pressed down on the brake pedal, man I caught hell getting the drum back on....