I have a 2002 F150 4.6L 4X4.

The other day a woman stopped in front of me, which caused me to slam on my brakes.

Ever since, my I find my brake pedal falling to the floor when I step on it.

They do re-gain pressure when I pump the pedal. But the pressure doesn't last long.

The fluid level is fine, and I don't see any leaks.

Any idea what I need to do to fix the problem?

 

maybe the brake booster is cracked or one of the vacuum lines are damaged. check if you can feel air around the booster when you step on the brakes

 

no no no

if the booster was bad it would result in a hard pedal... you wouldn't have any boost.

Sounds to me like you blew one of your seals in the master cylinder. My first guess would have been that you blew one of your flex lines, but you say your fluid level is not changing, so it must be one of the seals in the master cylinder.

Either take it to a shop or replace the MC yourself. The seals are not serviceable.

good luck!

 

Man, you can't change just the seals?

That sux.

I'll work on this tomorrow. Thank ya'll for the help.

 

OK, I replaced the master cylinder. Not only did I bench bleed the cylinder, I also bled each wheel four times.

This helped nothing. I have the same problem - the pedal falls to the floor once pressed.

Maybe the power boost? Hmm.

 

You must have a leak somewhere... could be a small drip and you'd feel the pedal drop.

If its just a drip you might not notice the fluid level dropping that fast.

Its still not the power boost.

 

OK, one month since I replaced the master cylinder.

And the peddle still goes to the floor.

Still no fluid leak, though.

Thinking now it might be the anti-lock brake pump.

Anyone?

 

NewsJeff,
I am having the same problem. Have you solved your problem and what was the fix?
I've changed my master cylinder, just like you did; no change. Took off all the wheels and checked for leaks on the cylinders;no leaks.

 

Go to this link for an article describing what is happening.

http://www.aal1car.com/library/abs_kelseyhayes_rwal.htm

 

Ed, your link comes up "not found".

I had the same type of problem once with my 96 Sierra, pedal would go to floor and brakes would barely work if I pumped it(found this out on the way to work one morning,lol). Anyway, I bled the brakes good replacing all the old fluid in the lines and the problem was solved. Water gets in the fluid over time which will render it useless once enough water is in the fluid.

 

Hey! the same exact thing happened to me in the same exact truck when a deer ran out in front of me! it goesto the floor but when i pump it it regains pressure and no leaks, ive also gone through 2 master cylinders and those werent the problem. Did happen to find outwhat is going on exactly?? Id really apreciate it

 

Were any bubbles coming out of the bleed ports last time it was bled? If no bubbles and no leaks, have a friend asist you in checking the brake hoses. Check for soft spots and bulges when the pedal is depressed. If it still looks good, you may need to have the ABS system bled at the local Ford dealership.

Good luck.

 

I had the same pedal falling problem. No system leaks, so I changed the master cylinder. That did not fix it. The problem was the ABS valve body had an internal leak, so the system would not hold pressure on the calipers. I changed the ABS valve body. That fixed the problem. Unfortunately, you have to buy the whole ABS unit. From Ford it is over $700. Your best bet is to search Ebay for one.