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2004 Ford F150 4X4

The truck stops fine but the brake pedal is very low, not sponge. According to several of the f-150 forums this is common to most f150’s. I have read where owners have done the obvious things i.e., master cylinders, pads and rotors. I have even read that many have solved this by extending the rod from the vac booster to master. What is a fix for what seems a common complaint. Thank you.

If it has drum brakes in the rear the first thing I would do is make sure they are adjusted correctly. Just because they are supposed to automatically adjust doesn’t mean they actually do.

May just be time for new pads and rotors aling with a brake fluid flush.

I believe this truck has rotors all around

I’d follow @Barkydog advice and start with the basics.

You should do a brake fluid flush every 2 or 3 years. I wouldn’t be surprised if you have a lot of air in the system right now

Do NOT do any modifications such as “extending the rod from the vac booster to master”

Whoever gave you that advice is a fool, and you should stop listening to them immediately

I wholeheartedly agree with db’s admonishment not to mess with the system design.

The rod in question goes through the diaphragm assembly managing valves that close off the chamber in front of the diaphragm from the rear chamber and venting the chamber behind the diaphragm when you press the pedal to allow the engine vacuum to assist you in braking, and then when you release the pedal, closing the rear chamber and opening the fore and aft chambers to one another to equalize the diaphragm pressure. This is mechanically connected in a non-adjustable manner via its housing to the housing of the master cylinder. The distance MUST maintain proper so that when the MC pistons are pushed to close the MC cylinder vent and pressurize the fluid, the valves in the booster are working in proper harmony with it.

Mess this relationship between the booster and the master cylinder up and you can end up with either a braking system that does not work properly or even a system that as you drive constantly progressively applies itself via the booster until it overheats the rotors, pads, and even calipers. You could even boil the brake fluid.

My suggestion would be to check for any TSBs that might have been issued on the subject, let a pro assess the system, and if it’s working properly get used to it.


I seem to recall hearing this was a designed-in problem (some might call it a feature) with certain Ford models in the circa 2005 era, especially their truck. I can’t recall however what the issue that caused it was. Maybe something to do with the ABS system? In any event, the brakes worked fine, just the pedal was low. One idea might be to temporarily disable the ABS, might be as simple as pulling a fuse, to see if that has any effect on the low pedal.

Here’s some generic info of diagnosing low pedal, but before you go down that route, suggest you do a little more research to see if this is a common Ford truck circa 2006 complaint, b/c I think there is a Ford specific low-brake-pedal issue and may require a shop w/ Ford scan tool expertise to help you get to the bottom of it. And it’s possible you may just have to live w/it. It seems like it is more an annoyance than anything.

My 03 had a stuck caliper that caused a lowish brake, along with worn out pad

Thanks to all. I bought this truck 2 years ago because it only had 55k miles thinking im in my 60’s and should last the rest of my driving life. The pads look good and considering the mileage didnt think about fluid flush but thats easy enough and i will mic the rotors just in case. Just because it has low miles doesnt mean its ok. I got tunnel vision by listening to 150 forums about strange fixes. Thanks again.

If its always been like that, I doubt you’ll be able to do anything about it. The low pedal is designed in by Ford for some reason. One idea, if you know someone with a similar vintage truck, try theirs to see if its the same amount of low pedal. Another idea if you think this is specific to your truck, besides the ideas above, a bad wheel bearing could cause it too. As an experiment you could clamp off all the flexible hoses at the four wheels and test how it affected the pedal height , that might provide a clue.

I don’t think the “pedal is designed in by Ford for some reason”

I think there’s air in the system

From the link below:

Ford had some issues with several models, including the F-150. There have been complaints about a low or spongy brake pedal that doesn’t get fixed after replacing pretty much the entire brake system.

2006 Ford F-150 Brake Actuator Rod And Master Cylinder - Truck Trend Garage

I wasn’t aware of that

We have some F150s of that vintage in our fleet, and I haven’t heard of such problems. Makes me wonder how common it is

My work truck is a 2003 f150 4wd, new brake job was top oof the pedal, pedal got down to half and high speed brakeing issues, failing was caliper stuck worn out pad, and repeat brake job and all is fine, not a systematic issue with my o3

My understanding is this problem seemed to crop up on F150’s around the time of the great recession, with the auto bail-out program, cash for clunkers, all that. Not sure what the issue is though. It could well be just normal operation, and the pedal just “feels” low, but really isn’t. How low the pedal “feels” depends in part on the geometric relationship of the driver to the pedal.