Jerry V.

My 2002 brake fade was discovered when my Auto Zany brake rotors rusted. The rust caused so many problems I cannot list them all. This rust was catastrophic. Avoid Auto Zany at all costs when considering purchase of new rotors. It was,perhaps,a piggyback of errors which led to my brake fade problems which included several trips to shops to determine a fix. With so many hands on my brakes in so many shops it is evident someone-somehow did not do it right. Now remember...I take more than reasonable care of my autos. No roding no baha and easy goes it for me. I figure an F- 4x4 off-road with some added backbone, treated well,will serve me well. Only after having new rotors (NAPA) and new pads (NAPA) done by a Tuffy dealership in Ft. Wayne Indiana. I suspect their proper evaluation good parts and the right bleeding was the job done right. I now have excellent braking. Time should tell. Seems it was not the ABS after all. But we shall see!!! Thanks for all the COME-BACKS....P.S. I'm not gonna spend TOP TOP dollar for the very best on this car. But I think good quality parts should be expected from Auto Replacement parts stores. Bring back good quality auto parts "MADE IN AMERICA".

Jktx21

I'm having a similar problem with my 2002 4x4 f150, 100k. Pedal is firm braking when at speed, but if stay on the pedal it fades almost to the floor. Had the system bled twice, no improvement. I talked with a ford tech, he said they have seen plenty of the ABS HCU go bad. Said there was some way to isolate the ABS side and see if it's leaking that way? Anyone have experience with this?

Good old Bill

A leaking dump valve in the ABS hydraulic unit will act the same as a bypassing master cylinder, exception being with the ABS valve bypassing, the pedal only goes to the same low spot, time after time but truck still holds its position. With a master cylinder bypassing, the truck will eventually start to roll (auto trans in drive).

The valve goes for an arm and a leg at the dealership. It seems junk yards get $100 to $150 for it. After trying two master cylinders and also a brake booster, I replaced the HCU (or valve) and corrected my soft pedal feel. Its not an electrical ABS problem, hence no ABS light. Keep us posted here on this thread or actually its best to start a new thread for better coverage.

Jktx21

Thank you Bill. My truck has those symptoms which sound like the ABS HCU valve. Will stop and hold, ABS system still works, pedal just fades to about 25% of it's range. I will probably just take it to the dealer, just in case it gets misdiagnosed as an expensive part.

I will start a new topic once I get the issue corrected with the fix.

UtahGuy

I have the same sinking pedal problem, and the truck does indeed start to roll if I don't push harder and follow the pedal down. Now I know where to start, thanks!

River1

Exactly right. The ABS has 2 fluid equalizing reservoirs for the 4 wheels. One is pressurized and one isn't. The problem is with the non-pressurized reservoir which is why the pedal will "fade" to the floor with no pressure increase or fluid loss.

What's both amazing and incredible is how little the amount of brake fluid is actually involved. Anybody who has had a basic physics class should remember the fluid dynamics lab's and the person who sent fluid shooting across the lab or into the ceiling with a force almost equal to a 22 short rifle. All the warnings and precautions never seemed to prevent it.

One unanswered question though is if the problem is electrical or mechanical? Unfortunately as it stands apparently there is no way to find out. The fluid to the reservoir is controlled by a solenoid but IDS information on the solenoid isn't definite and it's also not an interactive point. Learned this in another thread through a discussion with a Ford mechanic. Seems the only way there might be to find out is with the flight system where the history of the ABS is tracked in real time and then downloaded.

Also learned in another thread where someone had taken their truck into the dealer a number of times, spent a fair amount of money needlessly only to find out during the last visit there was an ABS\HCU program update that was never done on their previous visits. In fact it seemed like nothing was connected to their truck until they become demanding and made their frustrations known beyond any doubts. Then the dealer put the IDS to the truck.

FYI, whenever you take a vehicle to a dealer let them know you expect to be updated and educated on the information that is available to them. It just seems that with all the ABS problems discussed here and the frequency at which they are discussed, a lot of money is needlessly getting spent on assumptions. There also seems to be a hierarchy of dealership intervention. As you go back and back, a mechanic with more training and experience takes over. With brakes do your best to not settle for that. Do whatever you can to skip the rookies and get straight to the designated hitter. After all, this is about your brakes and not some irritating inconvenience.

River1

This is another interesting point about the nuances discussed about the ABS. Some have your problem where the breaking is effected by the pedal fade and with others, the truck stays stopped as the pedal fades.

Fair disclosure here, I'm guessing from what I have read about the breaking fade and general knowledge I have about ABS. I think the improper operation of the non-pressurized reservoir is creating and slowing exasperating the need for bleeding. When bleeding is mentioned the first thought is air in the lines but that's not always the case. In fluid dynamics and specifically fluid lines there is are effects called "cavitation" and "cyclic stress." A break system is by its nature a cyclic action and it's even further amplified by how ABS works with cycling on and off states that is the "antilock." In a way the need for bleeding is the result of the ABS doing what it was designed to do.

Also early ABS didn't seem to have this problem. The answer could be that early ABS was what's called an integrated system. Now ABS is almost all non-integrated. It's involved. Incomplete but simply, with integrated, both the traditional and ABS are fed, pressurized and powered by the same hydraulic circuit. Non-integrated, the fluid source and distribution is the same but the two systems are isolated from each other and the ABS is further pressurized with a vacuum line. Different manufacturers have subtle differences but the basics are the same. FYI and FWIW, A Ford mechanic told me that he thought Ford's ABS came from Bosch.

bobalouie58

Hello River1. I have had similar problems with the abs on my 2002 F150. I had 2 MC replaced and they tell me i must have air in the system from the ABS module. Do you know if i can bypass the abs all together and just use my standard braking system? I found a place that will rebuild the module for $89 but my budget will not allow this. Basically i want to isolate the abs module and not have my brake lines go thru it. I appreciate any advice.
Thank you,

Robert

Chuck Hawkins

My issue is, I had to rebuild the rear differential. I figured what the hell, I'll change brake calipers while i am at it. after all was done, my only problem left is, I've bled the brakes 6x each caliper, and with the truck started, my pedal goes straight to the floor. when driving, I can pump it 3x and it's enough to stop the truck. This wasn't an issue before I started all of my maintenance.all the fluid had dripped out. Hence the reason I bled each caliper 6x. Please Help!!!!

Jbrew

Might want to start over with a master cylinder bench bleed, reinstall then go through with a normal bleed. If the master has air, you'll never get it out of there purging each wheel over and over.