c3corvette77

Hello all. Just joined up and this is my first post. I have a 2005 F150 FX4 and the brake pedal is soft, always has been. I've complained to the dealer every time it was in for service during the warranty period and there was never a problem they could find. Now that the rig is out of warranty, has anyone else had a soft brake pedal and what did you do to fix it? Master cylinder isn't low and there's no obvious problems I can see.

Thanks

mattd17

hi, welcome to the boards.....

here are the steps to try. they came from another forum site, and several people have tried it and been pleased.



-Remove the two nuts holding the master cylinder to the brake booster, they are 1/2in bolts.

-Once the nuts are removed, slide the master cylinder straight away from the brake booster. As I mentioned before there will be alot of resistance due to the vacuum build up. You can rock the master cylinder back and forth and you will here the vacuum relieving, once it does you can slide the master straight back.

-Locate the rubber o ring and ensure it is still in place. It fits between the master cylinder and the brake booster.

-With the master cylinder pulled back(leave all lines and wires attached) just position it out of the way. You will clearly see a 7mm bolt that is threaded into the rod sticking out of the brake booster. The rod has a grooved shaft that you will need to hold with needle nose pliers to keep it from turning while backing out the 7mm bolt.

-Back the 7mm bolt out of the rod(counter clockwise) about 1/2 turn or how much you see fit. I tried half turns until I got the brake pedal to where I wanted it. It is possible loosen the bolt to much to the point where your brakes will drag, thats why I went in such small increments. It took mine about 1.25 - 1.5 turns to get it right.

-Bolt the master cylinder back in place and your done.

hope this helps you !!!

Mod (Ret.)

Very dangerous to do this proceedure!!!

MATTD17, not shooting at you for this suggestion, but this rod should never be touched. This puts the push rod further into the master cylinder bore, and consequently can cause brake drag, or brake lock up! Not the thing to do to compensate for a soft or spongy pedal.

The most common reason for a soft/spongy pedal is air or moisture in the brake line. Both do not compress within the brake lines, and could be causing your "soft pedal" condition. Take the truck to a brake shop; ask them to perform a flush/brake bleed. This will remove and replace the possibly contaminated brake fluid with fresh DOT4/5 fluid, and remove any possible air and/or moisture. Brake fluid should be flushed every 3 to 4 years anyway, unless you are using pure DOT 5 fluid, and the brakes have not been worked on (system was "opened" allowing air/moisture to enter).

UNDER NO CIRCUMSTANCES WOULD I ADJUST THE MASTER CYLINDER BRAKE ROD LENGTH.

Do yourself a big (and safe) favor. Ask a qualified brake mechanic if they adjust master cylinder rod lengths to compensate for a soft brake pedal. I'll bet you a steak dinner they firmly say no.

NGM

I agree with Bucko, even if he does drive a Westy... lol 4 wheel disc brakes will have a softer pedal than a drum brake setup because there is no adjustement to the brake pads, once they back off the rotor it takes more pedal to take up the slack so to speak. I disagree with putting in dot 5 brake fluid, unless all the hoses and seals are changed to accept it. Dot 4 is what I would reccomend.

mattd17

you guys are both MORONS !!!!! if you read the original post, you will see that he has had it to the dealer.... dont you suppose that if they have checked the brake system that they tried a fluid flush ?? that afterall doesnt require a specialty brake shop. and bucko..... the post i put up CLEARLY states to adjust in small increments so that you DONT allow for brake drag or hang up. and for you ngm.... as your pads wear down, that doesnt increase the gap between the pads and rotors.... the fluid will transfer from the reservior to the hoses puck the pads closer to the rotor to take up any "gap". thats why when you change your pads, you have to compress the pistons back into the caliper, which pushes the fluid back into the reservoir.

maybe the 2 of you should try a basic search on soft pedals for these trucks, and see just how many people have tried this very method, and have been extremely happy with the results, even after several unsuccessful attempts at the dealers.

the original post states that the truck has done it since day one (as have waaayyy too many other owners). so do you think that the trucks are coming from the factory with air/debris in the brake systems? not likely.... what is likely though, is that the booster rod isnt adjusted to the "perfect" length.... this would explain why some trucks are "fine" and others are "soft". simply adjusting the booster rod is a simple fix.

BUT... i will agree with you on one thing bucko..... if you ask a dealer if they adjust the booster rod, then yes, they probably will say no.... AND THIS IS WHY SO MANY OWNERS HAVE TO DO IT THEMSELVES AND THUS MAKE THE TRUCKS BRAKING SYSTEM SAFER !!!

ehamlett21

Just joined, first post. I was having the same problem on my '97 2-Wheel Drive F-150 4.6L w/ cruise control. The brake pedal was very spongy and had to be pressed to the floor to get any response. I replaced the Master Cylinder and bled the brakes from each wheel. I also noticed a leak on the T-fitting on the rear axle on the steel line that goes to the left rear wheel. I made a new steel brake line and installed it. After all this the softness of the pedal improved not at all.

I took the truck to my favorite auto shop, Allison's Auto Care www.allisons.com in Plano, TX, and they right away noticed a very easy fix and overlooked problem.

MY SOLUTION: The way I reinstalled the new master cylinder was incorrect (but done the same way as when I removed it, so incorrect to begin with). The mounting bolts on the brake booster had a nut between the booster and master cylinder and of course one on the outside of the master cylinder holding it on. This is wrong. The master cylinder is supposed to be seated flush against the brake booster with a nut on the outside of the master cylinder and another nut holding the RABS bracket in place.

I was very fortunate that this easily overlooked mistake was very inexpensive to be fixed/noticed by the properly trained eye.

Mod (Ret.)

Interesting that this post just came back from being "buried". I never saw the response from MATTD17.

I'm not perfect, but I'm no moron when it comes to repair; especially the braking system. Any person that lengthens the master cylinder brake rod to compensate for a soft pedal is the in the wrong.

Identify and repair the fault causing the soft pedal; don't compensate something else for it.

rick99601

sometimes adjusting the pedal rod is the only fix.

04-08's can come from the factory with a soft pedal due to there tolerances.

this should be the very last resort after all other brake servicing is done.

fastford04150

Hey bucco i think he's compensating for something else....

Thunderslide

Kind of begs the question: If it is not to be adjusted, why is it adjustable?