04 Expedition Brake Problem
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Freshman User
Joined: Jul 2011
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04 Expedition Brake Problem
During any normal driving and when towing my brakes work fine, but if I slam the brakes quickly I hear a whooshing sound somewhere near the floor of the truck and the pedal goes flat to the floor. The brakes still engage enough that it will throw you out of the seat. Once I pump the pedal it goes back up and acts completely normal. It's been happening long enough that I have a hard time believing it's a master cylinder. I don't lose any fluid, and brake pad wear is even. The rubber lines to calipers all appear in good shape. 6 Months ago I bled the brakes and had problems getting fluid from the rear DS caliper, but that straightened out after a couple attempts. Last weekend I re-bled everything, ran 2 pints of fluid, and everything came out clean. ABS seems to work fine on ice.
Any thoughts?
Any thoughts?
Senior User
Joined: Mar 2008
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I'm glad it's not just me! I mean, it sucks that it is occurring with both of your vehicles, but i have described it to my tech and he is puzzled to. No leaks, I have personally inspected the pads and they have worn even.
On thing though, the rotors are slightly warped. I order a new set and they arrived last week. It's going in to the shop on Thursday, so i'll know then if the rotors are the culprit. But I know deep down the rotors aren't the cause because i can make the pedal bottom out with the vehicle standing still.
On thing though, the rotors are slightly warped. I order a new set and they arrived last week. It's going in to the shop on Thursday, so i'll know then if the rotors are the culprit. But I know deep down the rotors aren't the cause because i can make the pedal bottom out with the vehicle standing still.
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Freshman User
Joined: Jul 2011
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Guess we're not alone. Those pads are pretty thick when new, I thought maybe the caliper pistons were retreating too far and there was too much travel so I replaced the pads. I bought new rotors but mine were fine so I didn't replace them. I've considered replacing the master but that doesn't make much sense either, and last time I worked on it we abused it enough that is would have caused failure if it were on it's way out. The rubber lines do appear good and if they weren't the brake fluid when bleeding should have been dirty. If it were the booster it would be an odd way for it to fail. Everybody I've run this past so far just shakes their head and throws out random ideas.
Laughing Gas
Joined: Jan 2003
Posts: 1,082
Likes: 40
From: Melbourne, FL
These trucks have a panic-assist feature that kicks in when you slam on the brakes. You may be engaging that and confusing it with a brake problem. I know on my 03, it sucks the peddle down to the floor, but stops the truck in a hurry. I don't know if I get the whooshing sound though, so that may be a difference that actually points to a problem.
Fleet Owner
Joined: Apr 2008
Posts: 24,316
Likes: 5,127
From: 0,0,1
To me it sounds like the dump valves on the ABS unit are leaking. Unfortunately the ABS unit isn't serviceable and you would have to replace the whole unit.
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Freshman User
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Broncoholic, thats what I was wondering, if there was some override to help keep you from going through the windshield if you slam the brakes really hard. The whoosh sound is probably the pedal moving quickly and for a longer distance, that's where it sounds like it's coming from and there are really no other brake parts on the floor. If it was truely a problem I cant imagine the brakes would still hold solid even with the pedal on the floor.
If it was an ABS dump valve I'd be losing fluid which I'm definitely not.
If it was an ABS dump valve I'd be losing fluid which I'm definitely not.
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Laughing Gas
Joined: Jan 2003
Posts: 1,082
Likes: 40
From: Melbourne, FL
I've only engaged mine once during regular driving, when someone turned in front of me at an intersection. I also engaged it when braking hard to break-in my new breaks. I recall noticing that the pedal quickly gets a soft feeling, not requiring as much force from the driver. I like it, definitely maximizes stopping power with ABS for a range of drivers. I'm certain I can push the pedal harder than my wife, but the panick-assist kinda equalizes that out.
Logistics Pro
Joined: Jan 2001
Posts: 3,740
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From: Central NYS
Broncoholic, could you elaborate on how this panic-assist feature works?
Laughing Gas
Joined: Jan 2003
Posts: 1,082
Likes: 40
From: Melbourne, FL
No, not really. It's something I read 5 or 6 years ago. In a thread, in an article on-line or maybe even in the owners manual. I can't remember any details about it, just that there is a panic assist. I'll be honest, it may even be something that only pertains to trucks with the AdvanceTrac, I dunno. I just know it exists and my truck has it.
Fleet Owner
Joined: Apr 2008
Posts: 24,316
Likes: 5,127
From: 0,0,1
Why would you say that? The dump valve diverts the fluid to a reservoir, not the ground.
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Freshman User
Joined: Jul 2011
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Thanks for the heads up on that and any more info would be appreciated.
Mountain Pass
Joined: Oct 2010
Posts: 241
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From: Albuquerque
No, not really. It's something I read 5 or 6 years ago. In a thread, in an article on-line or maybe even in the owners manual. I can't remember any details about it, just that there is a panic assist. I'll be honest, it may even be something that only pertains to trucks with the AdvanceTrac, I dunno. I just know it exists and my truck has it.
Tech Tip: Expedition/Navigator Unintended Brake Assist