Rear disc brake drag problem

Tiny
DWHEELER7676
  • MEMBER
  • 1995 FORD TAURUS
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 112,500 MILES
My '95 Taurus has a rear disc brake drag problem, as indicated by excessive heat and odor, smoke and/or pad/rotor wear/discoloration (and likely mileage), obvious when driven more than a few miles, right (R)side is more noticable than left (L), but both sides are similarly affected. I have seen very few posting on web about such a serious/annoying performance problem.

I have replaced the following without any effect: L&R side flexible brake lines (new), R side caliper (rebuilt), caliper bracket and slide pins (new), parking brake return spring (new), L&R rotors and pads, as well as the load sensing proportioning valve (salvaged). All with no change.

When jacked up and the road wheel removed, the rotor hub may be turned by hand with slight drag (deemed 'normal'), however if foot brake is depressed
the brakes are 'locked' (deemed 'excessive') until caliper is wriggled by hand.

What can account for this, how do I debug it and what is the cure? The car will soon be used for two new drivers about to enter the driving world so safety/reliability is a primary concern, but cost is also a consideration.

o-Brake fluid flush/replace?
o-Master Cylinder test procedures?
o-ABS test procedures?
o-TSB or known issues?

Please advise.
Wednesday, May 28th, 2008 AT 10:58 AM

10 Replies

Tiny
DWHEELER7676
  • MEMBER
  • 6 POSTS
Here's gif I referenced in previous reply:


https://www.2carpros.com/forum/automotive_pictures/195089_95TaurusBrakeExplodedView_2.jpg

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Monday, April 5th, 2021 AT 12:23 PM
Tiny
MERLIN2021
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These will be an extra if your pins are loose! If they are too loose get new calipers, the holes have spread, and may be allowing the caliper to cock and missalign itself.
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Monday, April 5th, 2021 AT 12:23 PM
Tiny
MERLIN2021
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Never mind on the plastic, thats a different model, you pins slide into the mount, and altho they should move freely, they should not be loose, the mounting brackett may be worn out...


https://www.2carpros.com/forum/automotive_pictures/62217_Brackett_1.jpg

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Monday, April 5th, 2021 AT 12:23 PM
Tiny
DWHEELER7676
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So, I've had a busy weekend. After reading a post about problems with the master cylinder [orifices being blocked], I replaced it with a rebuilt master cylinder from a local auto parts store, and while there, swapped the rebuilt right side caliper [which was still dragging] for another rebuilt one.

Upon reassembling and bleeding the system all seemed fine. Initial testing, with the rear end jacked up and road wheels off, indicated no brake drag after releasing the service brake pedal. My first road test however, was horrible. After only a five mile trip down a highway and back the smell of overheated brakes was evident, and now the LEFT wheel is the one affected, too hot to work on and visibly smoking.

So now what? Should I have the entire system flushed before proceeding further? If this were a common problem, I'm sure I would have read about it elsewhere. I'm seriously considering dumping the car, even after all this work and expense.
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Monday, April 5th, 2021 AT 12:23 PM
Tiny
MERLIN2021
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You still havent said if you looked at the fronts. Diagonal brake system. And if the ride hieght valve is set wrong you can get this, the is a pressure gauge used to measure the rear brake pressures, your must be too high, try re-adjusting the valve. Open the bleefer on that left caliper, does it spin? Three things back there that can cause drag, Hose, caliper, and parking brake cablee too tight, (pulling lever)And in your case, the hieght valve.
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Monday, April 5th, 2021 AT 12:23 PM
Tiny
DWHEELER7676
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  • 6 POSTS
The front brakes (pads and rotors) have always looked and operated fine, no discernable heating, dragging, or abnormal wear. Despite 'diagonal' braking circuits, only the rear brakes have ever been problematic (dragging/heating), both similary affected at about the same time(?).

My latest endeavour was to replace the only items on the rear I had not; the Left Rear caliper and its bracket. This "seems" to have fixed the Left Side dragging for the time being, and I am now running cool on both sides so far.

I still do not understand the failure mechanism which affected only the rear brakes (never the front), gradually, over time - manifesting itself as heat and drag - with the only visible defects initially being the aging rear flexible brake lines (softened, outer layers cracking, but never leaking). Brake fluid, while bleeding lines throughout all this, always ran clean, never appeared to be discolored or to contain any foriegn particles of any kind.

In summary, I replaced both rear side pads, rotors, calipers, brackets, pins, flex lines, and parking brake return springs in order to "cure" this problem. In addition (and I suspect it was not absolutely necessary to), I replaced the load height proportioning valve and the master cylinder (out of frustration and desperation).

Thanks again for your input[s]. (And for keeping your fingers crossed over the next few weeks). I would still be interested how extreme, or common, the steps I took were to fix this, from someone with more experiance in these matters.
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Monday, April 5th, 2021 AT 12:23 PM
Tiny
MERLIN2021
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Any time the flex hose is craked or dry rotted, replace em, the reson is on the inside, if a piece peels loose, it will act like a one way valve, pressure can go in, but not out!
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Monday, April 5th, 2021 AT 12:23 PM
Tiny
DWHEELER7676
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Not to beat a dead horse, but the dragging kept up even *after* both those hoses were replaced (which was the *first* I did to address the problem).

Would you dare to venture a guess that something like that could happen *elsewhere* in the system (like in the caliper, or master cylinder), despite liberal 'flushings' due to bleeding each brake circuit repeatedly (with no visible discoloration, crud, or particles ever seen in the recovery glass jar)?

Would a good brake flushing be advised in a situation like this, as a first step, and/or possibly have saved me some of my 'plug and play'? (For the next time.)

(Regardless, I'm still keeping my fingers crossed.) Thanks again!
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Monday, April 5th, 2021 AT 12:23 PM
Tiny
MERLIN2021
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If it's not caliper mounts, and not calipers or hoses, it IS either contaminates brake fluid, oil or tranny fluid added to master, causing swelling of the rubber seals, then it will be brake cables, or hieght sensing valve allows too much pressure on rear brakes, so try driving wth the parking brake cables disconnected. As a test, Or have Ford test the and adjust the valve! You need a pressure gauge to do it!
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Monday, April 5th, 2021 AT 12:23 PM
Tiny
VOLARE REPLACEMENT
  • MEMBER
  • 2 POSTS
I too have a 96 Taurus GL with 4 wheel discs. My hydraulic lines rusted and burst and while under there I noticed that the rear pads are worn for the 3rd time in 35,000 miles. A year or so ago I had replaced the emergency brake cable only to find out that the right rear caliper emergency brake lever was frozen. Replaced both calipers with new pads and a year later here we are again with worn pads (and a groovy rotor). I have found a place on-line called classictube. Com. Their site is down right now but they have an 800 number. They allegedly make OEM brake lines. Will save me time and or money against attempting to make them myself. Already got the replacement pads and rotors in place. I will keep you advised on my progress and hopefully the real deal solution for the excessive pad wear.
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Monday, April 5th, 2021 AT 12:23 PM

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