Brakes help

brilis · Jan 10, 2022

Hey guys, I have a 2004 EB with a 5.4 4x4. Just over 100K miles. All new brakes, I mean all new. Everything, pads, calipers, rotors. Master cylinder 3 years old. Not leaking any fluid. Works great 95% of the time. Every now and then if i have to hit the brakes hard, the pedal will sink to the floor and almost lock up the truck.

My mechanic says he can't figure it out. Any suggestions would be appreciated!!! Thanks!

Don Hall · Jan 10, 2022

Soft brake pedal 1979 F-250 - Ford Truck Enthusiasts Forums

1973 - 1979 F-100 & Larger F-Series Trucks - Soft brake pedal 1979 F-250 - While driving my truck last week, the brake pedal went to the floor when I came up on to a stop sign. Luckly, it was very early in the morning and no one was around. My first thought was the master cylinder. So I picked...

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Uberexpy · Jan 10, 2022

I’d have the codes for the ABS pulled. My ODBII scanner won’t communicate with my ABS. Just had both local dealerships pull the codes for my ABS warning light. One dealership started the scare tactic of bad master cylinder & booster. The other tried scaring me about bad wheel bearings. It wound up being a wire chewed into by a squirrel. (It stashed a walnut at the scene of the crime)

On a side note, I just had my first brake job done at 138k. They tell me this set of pads is warranted for life. . . We’ll see. . .

brilis · Jan 11, 2022

Thanks for the help guys.

whtbronco · Jan 11, 2022

I had this exact problem on my 2004 EB as well. Took me quite a while to figure it out, but my main issue is not likely yours. At 211k miles the original front pads had the rivets rust through and pad lining was kinda free floating on the backing plate. Usually the brakes were fine, sometimes not good at all. After replacing the pads it still seemed to happen, though far less often. Once I took my scanner and ran the ABS solenoid bleeding routine I got some air out and that resolved it. Air in the brake system may be the culprit, never before had I found air in a brake system cause intermittent issues.

Broncoholic · Jan 15, 2022

brilis said:
Every now and then if i have to hit the brakes hard, the pedal will sink to the floor and almost lock up the truck.

This sounds like the "panic" assist feature built into these trucks. It's been a while since I've read about it, so I don't remember the right name for it. In short, if the computer thinks you're making a panic stop, there's extra brake pedal assist that kicks in and does exactly what you describe - "pulls" the pedal down (no more than you actually push it, but it takes much less force from the driver than normal) and the truck stops as quickly as it possibly can. I think the computer looks for a rapid transfer from gas to brake pedal with heavy brake pedal to kick in the feature.

I've experienced this in my 2003. It sounds like your system is operating correctly.

plumcolr · Jan 15, 2022

Ditto on the above. My '06 would occasionally do it; I did some research and found out it's a boosted assist that comes in when you nail the brake pedal hard and fast. And yes it's scary as hell, pedal goes much further down, and with much less pressure.

Brakes help

brilis

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Soft brake pedal 1979 F-250 - Ford Truck Enthusiasts Forums

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