I have an '06 f150 Fx4 supercrew. 33,000 miles. I've been chasing mushy brakes for a while now and I really think my master cylinder may be the culprit.. I've had the booster hose recall done, turned front rotors , ceramic pads on the front, bleed brakes at 4 corners , the pads on the back still look good. I adjusted the brake pedal rod behind the MC.. That brought the pedal up some but still mushy.When i press the brake pedal I get this "squishing" sound.I've read alot about the brakes on these trucks , and i just can't accept that these crappy brakes are the way there suppose to be.Is there any truth to having to cycle the ABS module while bleeding to get air out?? How do i tell if its the MC?? The brakes don't pump up , they're crappy no matter how many times u pump them. Thanks guys . I love my truck but the brakes seem dangerous

 

Well..with that new of a truck,I wouldnt think the master cylinder would be "going South" but anything is possible.The "squishing" sound could be fluid getting past one of the seals in the cylinder.Unfortunately about the only way your going to be able to prove/dis-prove the master cylinder is replace it.
That sound could also be from a suction leak in the booster valve/connection as well.Im not sure,but if memory serves,there is a one-way valve that keeps suction on the booster.If im correct,this valve could be bad letting the engine suction leak out,rendering the "power brake" thing useless.....I AM shooting in the dark here,but it may be worth looking into.

 

Has anyone had to replace there master cyl. ??

 

Master cyclinder had to be replaced on mine 2 weeks after I purchased the truck new??

 

i know this is 16 pages but it may help

http://www.f150online.com/forums/200...-resolved.html

 

In my experience, if you hold light pressure on the pedal and it bleeds down, the MC seals are leaking fluid past. Mushy pedal usually meant some air in the system somewhere. I always bench bleed the MC before install. Some in the past have been a "beaaatch" to get the air out of.

 

how to tell if a master cylinder is bad?

Brakes don't work...

Sorry; had to

 

So is there any truth to having to cycle the ABS module while bleeding to get air out??

 

I never have when I've bled mine on several different vehicles with ABS. I see no reason why you'd have to.

 

I like for my brake pedal to feel like a brick when I step on it. My ’04 has 55,000 mi on it and the master cylinder has recently gotten a little squeaky and not solid as it used to be. I’ll probably replace it when I do the brakes.

 

If you don't get any air into it in the first place, there should be nothing special required. If you do, then you may be in for some fun...