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Discussion Starter · #1 ·
I'm looking to see if anyone can diagnose potential reasons for this...

First, the background. I bought this car used about four years ago and did require some initial brake service. It has front and rear brake pads. About two years ago, it suffered from the rear pads unexpectedly being ground to dust. I attempted a simple pad replacement and found I could not retract the rear caliper using the special turning tool as required. Taken to a shop, a professional mechanic found the culprit to be a collapsed flexible line into the caliper which was keeping it engaged.

Since then, until recently, the car has behaved nicely and has not caused any real trouble. However, it has developed a stopping distance problem. My stated example is if you were going 30MPH and a kid popped out in front of you on his bike, and you slam the pedal, he'd be under the wheels before you could get it stopped. It doesn't do a full lurch-passengers-ahead-stop; it's a weak, gradual stop, like a loaded 18 wheeler.

I took it to a shop. After a day, they blandly said "air in the system", and bled it out. While I believe it could have been, it didn't make much of an improvement, minor at best.

A month later, took it to a completely different shop. This time they did find a broken wheel bearing and, again, "air in the system." After only a month? This place was a little more thorough, insisting there were no fluid leaks, they tested the pedal for fall rate, etc. Again, no real improvement, however. They did suggest that if we weren't satisfied, "maybe" we'd try getting the Master Cylinder replaced.

So here's the facts:

  • The pads are in good shape; not new, but still plenty of material left. Even the shop said "your pads are fine"
  • The fluid reservoir in the Master Cylinder is full and never seems to lose any fluid
  • Engine on or off, the brake pedal never reaches the floor; I can still fit my size 13 shoe underneath it at full application
  • The pedal does not slowly sink, as I've seen a suggestion of a bad Master Cylinder
  • The car does not pull to one side when brakes are applied, to suggest a stuck caliper
I'm at a loss. Assuming both shops are not giving me a BS answer, and air is repeatedly seeping into the system, where could that come from? Does replacing the Master Cylinder make sense? Could the calipers be bad or some reverse form of flexible line blockage?

I'm open to attempting to replace components, although I've never done it on my own before (always had my dad around to help many years ago), so I know the gist of it and I know I could save money, as long as I feel confident what I'm trying to do will have some effect. But I just don't get a strong feeling right now based on what I know. I would take it a shop again, but I'm afraid it will just be more "air in the system" and nothing gets done.
 

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Cake monster
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I'm looking to see if anyone can diagnose potential reasons for this...

First, the background. I bought this car used about four years ago and did require some initial brake service. It has front and rear brake pads. About two years ago, it suffered from the rear pads unexpectedly being ground to dust. I attempted a simple pad replacement and found I could not retract the rear caliper using the special turning tool as required. Taken to a shop, a professional mechanic found the culprit to be a collapsed flexible line into the caliper which was keeping it engaged.

Since then, until recently, the car has behaved nicely and has not caused any real trouble. However, it has developed a stopping distance problem. My stated example is if you were going 30MPH and a kid popped out in front of you on his bike, and you slam the pedal, he'd be under the wheels before you could get it stopped. It doesn't do a full lurch-passengers-ahead-stop; it's a weak, gradual stop, like a loaded 18 wheeler.

I took it to a shop. After a day, they blandly said "air in the system", and bled it out. While I believe it could have been, it didn't make much of an improvement, minor at best.

A month later, took it to a completely different shop. This time they did find a broken wheel bearing and, again, "air in the system." After only a month? This place was a little more thorough, insisting there were no fluid leaks, they tested the pedal for fall rate, etc. Again, no real improvement, however. They did suggest that if we weren't satisfied, "maybe" we'd try getting the Master Cylinder replaced.

So here's the facts:

  • The pads are in good shape; not new, but still plenty of material left. Even the shop said "your pads are fine"
  • The fluid reservoir in the Master Cylinder is full and never seems to lose any fluid
  • Engine on or off, the brake pedal never reaches the floor; I can still fit my size 13 shoe underneath it at full application
  • The pedal does not slowly sink, as I've seen a suggestion of a bad Master Cylinder
  • The car does not pull to one side when brakes are applied, to suggest a stuck caliper
I'm at a loss. Assuming both shops are not giving me a BS answer, and air is repeatedly seeping into the system, where could that come from? Does replacing the Master Cylinder make sense? Could the calipers be bad or some reverse form of flexible line blockage?

I'm open to attempting to replace components, although I've never done it on my own before (always had my dad around to help many years ago), so I know the gist of it and I know I could save money, as long as I feel confident what I'm trying to do will have some effect. But I just don't get a strong feeling right now based on what I know. I would take it a shop again, but I'm afraid it will just be more "air in the system" and nothing gets done.
"This time they did find a broken wheel bearing"

I hope you asked them to demonstrate the play or noise before replacing it. I'm not great at diagnosing brake issues. Does the car have ABS (just so we know)? If not, can you lock the brakes by stomping the pedal? I thought air can only get in when there's a leak somewhere in the system, maybe someone can chime in with a good answer.

Vacuum leak?
Bad master cylinder?

Those are my only guesses.
 

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If the car has rear disc, it has ABS.

So from what you're saying, if you mash the brake pedal as hard as you can, you don't have the ABS kick in, and feel the rumbling in the pedal of the ABS rapidly pumping the brakes to stop the car?
 

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Discussion Starter · #4 ·
If the car has rear disc, it has ABS.

So from what you're saying, if you mash the brake pedal as hard as you can, you don't have the ABS kick in, and feel the rumbling in the pedal of the ABS rapidly pumping the brakes to stop the car?
I just tried again, but it's true I don't really feel the rumble. Of note the "ANTILOCK" light does illuminate at lamp test but goes out, so I assume the electronics at least think it's in working order.

I also tried an experiment (and I apologize in advance if this was a bad idea somehow) where I got it up to speed on a straight stretch of road, put it in neutral and killed the engine (to get ABS out of the picture), and slammed it. Honestly didn't feel all that much different compared to engine on.

I always thought that the presence of ABS was just to prevent the wheels from locking, that the absence would mean I could potentially lock. Is that an incorrect assumption?
 

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I just tried again, but it's true I don't really feel the rumble. Of note the "ANTILOCK" light does illuminate at lamp test but goes out, so I assume the electronics at least think it's in working order.

I also tried an experiment (and I apologize in advance if this was a bad idea somehow) where I got it up to speed on a straight stretch of road, put it in neutral and killed the engine (to get ABS out of the picture), and slammed it. Honestly didn't feel all that much different compared to engine on.

I always thought that the presence of ABS was just to prevent the wheels from locking, that the absence would mean I could potentially lock. Is that an incorrect assumption?
Every ABS I have owned, had a way to turn it off. My '01 and '03 now and my has been '95 has a switch. With my Lincolns you have to push buttons on the menu. Possible on dry pavement that it is hard to lock up a wheel. I would try on gravel road, ABS on, and ABS off with the switch. Turning the engine off may cause you to have not enough vacuum for full brake.

Good luck.

-chart-
 

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Seeing as how in your initial post your complaining of the brakes not slowing the vehicle very well, it sorta makes me want to suspect the vacuum brake booster!!!???
 

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chart, i don't know of any switch available on a Taurus or Sable ever. You could pull the fuse for ABS if you want to enable/disable it. Good idea on the gravel or dirt road, prevent tearing up your tires. It appears the self test is working on run, a good start at least. If the ABS system dedicated an issue, it normally would illuminate on an OBD-II vehicle, unsure on an OBD-I vehicle.
 

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Discussion Starter · #8 ·
Seeing as how in your initial post your complaining of the brakes not slowing the vehicle very well, it sorta makes me want to suspect the vacuum brake booster!!!???
I know the gist of what this does, i.e. assisting in the human-applied braking power, but I'm interested in how likely this might be a source of the problem.
 

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ABS switch

chart, i don't know of any switch available on a Taurus or Sable ever. You could pull the fuse for ABS if you want to enable/disable it. Good idea on the gravel or dirt road, prevent tearing up your tires. It appears the self test is working on run, a good start at least. If the ABS system dedicated an issue, it normally would illuminate on an OBD-II vehicle, unsure on an OBD-I vehicle.
Pic of ABS/TC control shutoff switch.

-chart-
 

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That button just turns off traction control. ABS will still operate with TC turned off.
 

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I know the gist of what this does, i.e. assisting in the human-applied braking power, but I'm interested in how likely this might be a source of the problem.
Well if you have to mash the brake pedal really hard, you know, how it feels when you mash the brakes without the engine running & there is no vacuum to the brake booster, so you really have to mash hard to get useable brake action. Now I'm not suggesting your problem is that gross, but you get the idea, if you really have to get on the brakes hard to get action with the engine running, then maybe the brake booster has a vacuum leak & isn't offering up it's full boost assist?????

SO, you could disconnect it's vacuum line, attach a hand vaccum pump, like a mighty-vac, or the like, that has a vacuum gauge attached, pump it to say 20-25" vacuum & see if it'll hold that figure, or if it leaks right down, or if it leaks so bad you can't even get it to 20" of vacuum. (Make sure your hose connections are leak tight) If you can't get it pumped down, or the brake booster won't hold 20-25" of vacuum, replace it & let us know how it goes.
 
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