Replaced pads and rotors, brake pedal sinking to floor now?!?

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Trainmaster

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My 08 had spongy brakes which replacement hoses helped a bit. The brakes still tend to sink when applying pressure after a stop. When I release them and press down they come up a bit again. They won't sink anywhere near the floor but they sink none the less. I've adjusted the booster pushrod (which may not have been mentioned here but is one service cure) and it may have helped a little more. After reading these and F150 forums, I've accepted "spongy feeling brakes" as a normal characteristic of these trucks.
 

07navi

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Mine is spongy too and I also just accepted that they will sink a bit if you press them hard. It always stops fine, especially after I flushed all the fluid.
 
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UniqueTII

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I can get used to spongy, but this is way worse than anything I've experienced with this truck before. I get almost no feedback from the pedal until I'm about at the floor.

Messing with it again tonight, I pinched all 4 brake lines and got good pedal pressure. I released the clamps on the rear lines and I'd get slightly more pedal travel but no sinking. Opening up either of the front lines would result in the pedal losing pressure and sinking to the floor. I pulled the wheels and noticed a strange contact patch on the outer passenger pad where it looked like the outer 1/3 of the pad wasn't contacting the rotor enough to clean it off. Not sure what to think of that, but the driver's side looked better. I didn't really notice anything else odd with the pads, rotors or calipers. I was going to start putting old hardware back on but I realized that I already threw away my old pads.

One thing that was recommended that I've tried before is removing the vacuum going to the booster, which results in a solid pedal. I did that again tonight with the same result, but I can't wrap my head around how a failing booster would cause this issue, but I have heard people with other makes of vehicles say that it did for them. The vacuum pump is pulling 25inHg so I don't think that's the issue.
 
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UniqueTII

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I've read about a few other people having this issue, specifically with Powerstop brakes. One of the stories I read stated that the pedal firmed up after about a week of driving, so the assumption was that the pads and rotors weren't parallel (which would make sense given the uneven wear I observed above). I went out and did a bunch more hard stops with it but haven't noticed any improvement yet.
 

Langer

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I've read about a few other people having this issue, specifically with Powerstop brakes. One of the stories I read stated that the pedal firmed up after about a week of driving, so the assumption was that the pads and rotors weren't parallel (which would make sense given the uneven wear I observed above). I went out and did a bunch more hard stops with it but haven't noticed any improvement yet.

When I did mine, I didn’t love how the pedal felt, I thought I messed something up (this was my first brake job solo). After doing the break-in procedure, I was back to a comfortable feeling in the pedal. I know that doesn’t help you much except to confirm what you’ve already read online, but maybe try the break-in procedure, again?
 

riphip

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I've not had any problems with my Powerstop brake setup. I have experienced a need to use the anti-lock braking system since install :mad:. Truck is 16 years old w/original calipers,MC & booster. Will change all of that at once when time comes. Accruing parts a little at a time at present.
I have already changed all the vacuum lines, etc after I bought it. Knew what kind of problems those would cause if unchecked.
 
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UniqueTII

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Thanks guys! I did go do the break in procedure again and I think it feels a little better (or maybe I just want that to be true...haha) but it's still super easy to push it straight to the floor. Having to hold it for ~30 seconds is more like what I'd expect! I don't think it's a safety issue at this point since the brakes stop fine unless they're super hot, so I'll drive it this week to see if it keeps improving.

Not sure if I already mentioned this, but I thought about putting the old rotors and pads back on the front to test if that was the issue but I already got rid of the pads, unfortunately.
 

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