Three places I would check would be the flex brake lines going from the frame to your front disc calipers, and any vacuum hoses that supply your brake booster. The flex lines will get soft with age and "give" when the brakes are applied. Feel of them while someone is stepping on the brake pedal to see if they increase in size under pressure. If they do, they need to be replaced.

Any vacuum line that is split or leaking that is on the vacuum side of your power brake booster will result in a low pedal, and spongy initial feeling. The line will run to the intake manifold of your gas engine. If you have a diesel, it will usually come from a vacuum pump. The booster's diaphram can also be checked for leaks. If it is ruptured, it will not hold a vacuum, will make full actuation of the master cylinder difficult, and can result in a low pedal.

Gard

I think your truck's brakes are boosted off the power steering pump... When asking a question about a certain vehicle, list the make and model... All truck brakes aren't made, built nor do they operate the same.

Everyone has a different definition of "low", but all the Hydraboost equipped trucks Ive driven (including mine) have a pedal feel of somewhere between marshmallow and just plain suck.  Ive been told the Hydraboost "feels" different, yeah I'll say.  Ive never run into anything, but the pedal is not confidence inspiring.

Since you live in MI, you will have more corrosion than I do in SC.  There are some issues with pedal feel problems caused by binding calipers.  Mine are fine, you should take a look at yours.  The brake pad ears and slide bolts need to be free of corrosion and greased so they move freely.

I got the same setup.... I don't really have pedal until it's at half pedal... It stops just fine but it seems to take a little more leg than what I was used to before this "hydra-boost" setup. The old vaccume/hydra-vac setup was hard to beat. My old 1988 7.3 F-250 has a seperate vaccume pump and those brakes will make you eat the steering wheel if you get on the hard!!

Coming back to this subject of soft brakes, I flushed my power steering fluid and brake fluid in the Dmax..........again.

This time it WORKED.  No more half way down, or spongy pedal.  I have brakes from the instant I touch the pedal, just like every other non hydra boost vehicle did.

Would be worth a try for anyone with GM's hydra boost system.

Originally written by mingiz on 2009-05-16 7:49 AM

I just changed the pads on my F250 SD 6.0. I get the same petal feelings. The pads that I took off didn't look worn at all for the truck having 50K. I'm taking it for a test run today with the lq hooked up. It stops but just isn't the same as it was. Like someone said gotta use more leg. Rotors were fine. It just doesn't give me that stop on a dime and give ya change back anymore.  And I don't like it...

If you didn't turn the rotors, then it may take some time for the new pads to "seat" to the rotors, (makes for a spongy pedal until they seat).... If they don't seat, you may have to pull it all of, turn the rotors and replace with new pads.