Another fading break pedal problem 2003 F150 4x4 supercrew. My breaks at a red light in gear with foot on pedal will start to fade you feel it going down very slowly. And it starts to creep forward unless you lift your foot and pump real quick. I changed the Rotors and pads. Pedal got higher but same problem. Took it to the shop for a flush and bleed. They also changed the master cyl. Same problem does the same thing the breaks just feel better. But pedal still fades slowly. Don't have the cash to just starting changing everything. Its like it looses vacuum. You think the booster pump is shot

 

You sure you don't have a leak somewhere? Hose, caliper, rusted brake line, etc?

 

No leaks that i can see no lost of fluid. This is crazy if i go for a 5min ride and home its fine. But if you go on a long ride the pedal will fade when stopped waiting for the light to turn green

 

Almost sounds like a booster issue, or the brakes not bled all the way. Or a crazy thought... Shot brake hoses expanding under constant pressure. Stranger crap has happened.

 

This ^^^^^

 

Should I go with stock replacements or price out braided brake lines.

 

Matter of opinion and budget. Nothing wrong with stock replacements.

 

Replace the master cylinder. You are describing the textbook symptoms of one failing. The internal cups are beginning to leak past in the bore. Next will be the pedal drops to the floor without warning on making a stop. If no leaks are visible and pedal falls or creeps any amount or any time ( customer complaint is usually my brake pedal went to the floor but it only did it once) immediate replacement is needed.

Booster failure will result in a hard pedal and higher than normal pedal height. I have never seen brake hoses swell with over 40 years in the industry, only replacing them for deterioration (cracks and the like) or physical damage.

Driving with this condition is like kissing a rattlesnake. Sooner or later you are going to get bitten!

 

Interesting. This is a known issue with the F-150 that causes a spongy pedal.

 

I've found master cylinder failure to be the problem when experiencing the symptoms you describe. I would strongly suggest replacement and soon....real soon or park it.. I've had the same failure 3 times now on my Bronco and once on a 2002 SCrew. A NEW master cylinder was the cure. I would not suggest or recommend a rebuilt unit, hence the first 2 on the Bronco.

Shouldn't be. The brakes hoses, at least the factory installed units, are rated as SAE J1401. The spec calls for limited expansion of 0.06 per ft at 1000lbs pressure. That certainly won't cause a spongy pedal. If the hoses were the issue, I doubt the anti-locks would work at all. Maybe with a cheap after market part it could be an issue. As we all know, not all parts are created equal.

 

The shop changed the master cyl if you read my first. Truck still does the same thing like I said it's only on long rides. Quick rides up the block and home it's fine

 

If the booster was bad, it would just get a very hard pedal, no braking assist. The pedal would not go down. It has to be air in the line or fluid not keeping full pressure. That means master cylinder or ballooning brake line.

 

They may have replaced the master cylinder with a rebuilt unit. I had to find a Motorcraft unit before I solved the issue on the Bronco. Just because it's new doesn't mean it isn't defective.

 

But but but - shopteach and Labnerd say this isn't possible!

 

Just not the most likely failure, I guess anything is possible, just never seen it. I have seen MANY reman parts including master cylinders defective. New OE part is recommended.
GLC , pm me and I will tell you my qualifications to make this statement. I am trying to help , not to hear smart a** comments. I only make a living knowing this type of info.