Brake problem - hard to diagnose - Car Troubleshooting


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Brake problem - hard to diagnose

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Guest
Anonymous Poster
freya44@yahoo.com

Sep 4, 2008, 6:11 PM

Post #1 of 4 (2635 views)

Brake problem - hard to diagnose	Sign In

I need help understanding what could be causing a brake problem in a 1998 Ford Taurus. This is my teenage son's car. He left for work one day and came back a few minutes later saying when he made his first stop, the car took much longer to stop than normal and seemed to slide to a stop. I took the car in to be checked right away and the shop said they couldn't find anything wrong. They did charge for cleaning and adjusting the back brakes. The next time he drove the car, he ended up rear-ending someone because he couldn't stop in time. Luckily he was only going 5 MPH. I took it to another shop and they also said they could not find anything wrong. They said they checked for master cylinder problems and couldn't find any. There is definitely a problem - when you step on the brake pedal, it goes almost all the way to the floor before it stops the car. This happens all the time - even the first time you brake - so it's not something that gets worse with each subsequent stop. Pumping the brakes doesn't help. I can drive down the street with the pedal depressed half way down to the floor and there is no reaction from the brakes at all. The only way to safely drive this car is to start braking well ahead of when you would normally start to brake. In an emergency stop, you are out of luck which is why I won't let my son drive the car anymore. If we can't get this fixed I am going to get rid of the car and get another one which we really can't afford right now. Other than the brakes it is a good car. Any suggestions? Thanks - Marie

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Anonymous Poster

Sep 4, 2008, 7:02 PM

Post #2 of 4 (2622 views)

Re: Brake problem - hard to diagnose	Sign In

Wow.... That is strange 2 seperate shops couldn't find anything going on.....

I would suggest to take it in and go on at test drive with the tech...or at the minimun talk to the guy doing the work. I've had probs in the past where important info doesn't alway get passed on....usually on drivabilty, not brakes.....

I'm not going to 2nd guess anyone but that is strange nothing could be found on what sounds like a pretty obvious hydraulic problem

Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Sep 5, 2008, 4:43 AM

Post #3 of 4 (2613 views)

Re: Brake problem - hard to diagnose	Sign In

Agreed - don't drive this car till this is solved. First shop cleaning and adjusting rear brakes (if drum) is a reasonable shot at this if it behaved when they were finished with doing that.

This is reason enough to just up and replace the master cylinder and bleed out the system. There could be a false signal from anti-lock brakes going on and would expect a light or error code noted but who knows for sure.

Master cylinders can do this by themselves and might behave for a test and hard to blame unless witnessed when it's known that air in the system is not or could not be the problem. Allow extended testing by the shop who tackles this to be as sure as possible that this problem is truly fixed,

T

DanD
Veteran / Moderator
DanD profile image

Sep 5, 2008, 5:24 AM

Post #4 of 4 (2610 views)

Re: Brake problem - hard to diagnose	Sign In

If the master cylinder and the brakes at the wheels have been checked and are functioning properly; I would suspect the ABS control unit.
Inside the ABS unit there are accumulators that are designed to store pressurized brake fluid, during an ABS stop.
What I mean is; if the system is working as intended and you’re into a hard stop with one of the wheels beginning to lock-up. The ASB system sees this and opens up a valve in that wheel’s hydraulic pressure line and relieves the pressure to that wheel. That pressurized fluid is directed to an accumulator (storage container) relieving the pressure on that wheel. Once the ABS event is over, the fluid in the accumulator is allowed (pushed) back into the system, under low pressure; the accumulator absorbed the pressure.
Each wheel has an accumulator inside the ASB unit; if one of the valves that directs the fluid to an accumulator is stuck open or leaking; the pressure you’re trying to build by pumping the brake pedal is just transferring to an accumulator and not transferring the pressure to the wheels.
Last I checked the ABS unit is not serviceable and the complete unit would need replacing if this is the problem with your sons car.

Dan.

Canadian "EH"

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