Hi All,

Long time lurker, gotten a lot of help from reading threads on this forum and thought I should start sharing a few things I've learned on my own too.

This is my first FYI for you, it's lengthy, but hopefully it saves someone some work.

I've had three 04-08 F150's, an 05, 06, and now an 07. All have been black FX4's with various cab configurations and amount of lift and mods. All have suffered from a soft / spongy brake pedal that has driven me nuts. I've tried it all (aside from going to the dealership for a bleed, DIY'er to a fault I guess).

On all three trucks I seized brake caliper pistons. I'm a believer now that as part of preventative maintenance, brake fluid needs to be changed every couple years. I think the contaminated fluid is a big contributor to the seizing pistons issue. I've got a Motive power bleeder now to help that process. So that's one lesson learned, but onto the bleeding.

After a caliper piston seize, changing all calipers (so having lots of air in the sytem to contend with), and bleeding the brakes, my pedal has been even softer than it was too start. Same with all of the trucks and it wasn't great to start with on any either. And by soft I mean too much total pedal travel and too much travel before pad engagement. Tried the 2 man brake bleed method, well one man and one wife method. Work from furthest caliper to closest to master cylinder. Assistant pumps the brake, holds the pedal, stick a block under pedal to resist going to floor and close bleeder before reaching end of travel, don't let master cylinder run dry. After many rounds of this and a strained marriage from all of the yelling I was convinced to get the one man Motive power bleeder.

Hooked up the Motive, 15-20 psi, worked on calipers in same order. Lots of bubbles, still lousy brakes. 10 bottles of brake fluid later, lots more bubbles, still lousy brakes. Don't get me wrong, I'd see a slight improvement with every bubble I got out, but it seemed the improvement would degrade quickly after cycling the pedal a few times when driving.

Got to a point I thought all the bubbles were gone and thought I'd try the master cylinder / booster adjustment rod tweak. Helped a little, but went back to another bleed and got more bubbles. So this wasn't my issue.

Found a gravel parking lot. Worked the snot out of the ABS going forward and back thinking I had air in my ABS module. Bleed again, repeat, repeat, more bubbles, repeat, no more bubbles, improvement but still lousy brake and getting sea sick from all the antics in the parking lot.

At this point I was thinking the master cylinder was bad or I somehow got air all the way up to it. Tried a method of using the Motiv, pressurizing, and pumping the brake while bleeding (rather than pulling the MC and bench bleeding). Still no dice.

On a previous F150 I also replaced the soft rubber lines running to the calipers. All have had notable rubber looking contamination in the brake fluid, but the new lines didn't help on that truck so I skipped it with my latest endeavor.

My tab on brake fluid was well over $100 based on how many containers I'd gone through at this point and I was just about to throw in the towel and try the dealer. They can cycle the ABS while bleeding, replace the MC, whatever it takes. Didn't want to live with a soft pedal this time.

I decided one last try, more frustrated than ever. I first pumped the brake, with engine not running, until hard. Hooked up the Motive, pumped up to 20 psi. This time, I decided to hit the caliper housings with a rubber mallet while bleeding. I'd done this before but light taps. The frustration brought out some rather hard pounding this time. I noticed quite a few more bubbles than I'd seen before. Hopelessly optimistic I hopped in the truck. I finally had a decent brake pedal! Fingers crossed, but it has been a few days and I haven't lost it! It's like driving a different truck.

So, don't know if it's the shape of the calipers, the location of the bleeders, or cavities inside them that trap the air, but if you're looking to give something else a try for the soft brake, try some semi-forceful hits with a rubber mallet while bleeding (definitely wouldn't use an actual hammer for fear of deforming the caliper).

I think some combination of all the techniques above have got me to where I want to be, but the rubber mallet on the calipers made the biggest difference in feel after trying it all.

Hope this helps and I've got a few other "lessons learned" I'll share when time allows!

-Nick

 

So it's been a few months, is the pedal still firm? I have an 03 and have been fighting a soft pedal that came on a few months ago. about 5 qts of fluid and 2 master cylinders

 

Definite improvement with the mallet tapping while bleeding, but I still wasn't totally satisfied.

Pulled the master back off and adjusted the rod 1/4 turn at a time. Ended up at 3/4 of a turn total. Did another bleed right after that, waited a week and bled again, then one more bleed a week later. It has been a couple months since the last bleed, and knock on wood, I haven't been tempted at all to mess with it anymore because I've been happy with the feel.

Now we'll have to see if during the winter, the first time I slide on the ice and abs cycles, if the pedal softens up again. Then I'll know there's still air in the abs module. Hope not...

 

if you take it on a gravel road you can get the ABS to cycle by getting a little speed and hammering the brakes. 20-25mph is sufficient. I've done that myself, I also have a friend with a snap-on scan tool that will do it electronically

 

Sorry to hear of the frustration of the pedal firmness. I bled mine 3 years ago with the one man method, worked great and it stops great. I never ran my engine during or anything.