Weak Brakes - Please Help

[AngryBird]

Time to revive this thread. After almost a year, Ford has not provided any solution to the problem we are having. When we first start our expedition in the morning, we experience the issue. It happens intermittently (not on every cold start), and so is hard to reproduce reliably.

My wife puts her foot on the brake, starts the Expedition, moves the shifter to reverse (or drive depending on which direction she is parked) starts down the driveway by lifting off of the brake pedal. When she tries to re apply the brake at the end of the driveway, it feels as if the power braking system has lost vacuum to the booster and is extremely hard to stop before the vehicle runs into the road (and traffic b/c we live on a busy street). Based on my previous experience with vehicles, it seemed like this might be a bad vacuum check valve that is releasing the vacuum in the booster after it sits over night. I paid out of pocket to have a local mechanic replace the check valve (Ford OEM) and the very next morning we had the same problem again.

I took it 100 miles to a Ford Dealer in Albuquerque. They service writer (so therefore scumbag) told me he has seen this problem before and a simple computer update will fix it. I asked him to explain to me how the computer controls the vacuum going to the brake booster and he could not. I dropped the issue as to not piss him off. He took the vehicle and had the update applied. He assured me again that it would fix the problem. I drove the expedition another 100 miles home and it happened to my wife again this morning.

I'm not sure what I should do now because I don't want to take it back only to have them tell me that there is no issue (or that they couldn't reproduce it) and waste another trip.

 

[toms89]

What you stated in your first post about the pedal hitting the stop or floor has me believe there is something wrong with either your master cylinder or antilock brake system. The brake pedal should never go to the floor. Since it appears to be intermittent I am thinking your antilock brakes are releasing the pressure as if it were locking up even though it is not.


I used to drive a chevy van at work and if I hit a bump while moderate braking the same thing would happen. Brake pedal would drop to the floor forcing me to pump it.

I knew that absolutely had to be an issue with the anti lock brakes but the dealer never did find anything wrong as they could not duplicate the condition.

Have the mechanic back it out of your driveway......
Some issues are hard to diagnose unless the condition can be readily duplicated.

 

[stamp11127]

I would bet you have a leak. One of the old tricks is to **** the fitting on the brake booster to see if the vacuum is released. If you hear a hiss it is holding vacuum. Don't know if they have changed the design on the newer models though.

Check the hose from the intake manifold to the booster for leaks. If there is a leak the vacuum will be lower than normal until it builds up.

Another clue is a hissing sound inside when the engine is turned off. If you hear it the booster is leaking.

Don't know about auto abs but on the big trucks they do have an abs ecu which can be updated. The service writer may be correct if the autos also have an ecu controlling the abs.

 

[FordandPolaris]

Unplug the ABS fuse and see if the problem goes away, that would confirm or deny tom's theory. I had a problem with the ABS kicking in on right hand turns a couple of years ago. Pulled the fuse and solved the problem.

 

[RI-Matt]

)
My wife puts her foot on the brake, starts the Expedition, moves the shifter to reverse (or drive depending on which direction she is parked) starts down the driveway by lifting off of the brake pedal.

Did I miss something ?
Why is she putting her foot on the brake BEFORE starting the Expy ??




Matt

 

[stamp11127]

I've been doing that for the last 40 years out of habit. Before the auto makers had to protect the stupid drivers of today with all this safety crap, we could start in any gear. Got real exciting at times!!! Hence the foot on the brake.

Ahhh the good ol' days of no neutral safety switches, no clutch switches and steel cars with real Honest to God horse power. Not to mention 104 octane gas at your local Hess gas station.

 

[GAINMOB]

check the ABS box and make sure the fittings are secure...my k&n shroud just busted my lines...cant miss the box...right under the filter

 

[GAINMOB]

check that...MC...brake booster...i changed brakes and master cylinder went bad...changed that and the brake booster went bad...

 

[capitlj]

Ok your problem is definitely NOT the booster. The vacuum booster just "boosts" the line pressure coming out of the Master Cylinder so you dont have to push the pedal so hard to stop. Symptoms of a bad booster would be hard pedal not a soft one. As was said above under no circumstances should you be able to push the pedal to the stop. The ABS theory is the only one that makes any sense to me and like was stated is easy to test by pulling the fuse. If there was air in the lines you'd have a spongey pedal vacuum or not. If the Master Cylinder was bad it wouldnt hold line pressure under any conditions i.e. you would always be able to push the pedal to the floor vacuum or not.

 

[fordanator]

What brought me to this site is the very same complaint.. first start up of the day and backing out of the garage. Only happens to us though on first start up...all fine and well after that until the next morning. Weather does not make a difference for us.


any updates or clues????