95 Taurus GL Rear Disk Brake Overheating Problem

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SQUIRE - 27 May 2006 18:29 GMT

Periodically over last 6 years I have had problems with rear disc brakes on
95 Taurus GL 4 dr. sedan with extra weight besides one driver.
Replaced Emergency Brake cables, Front/Rear proportioning surge valve, both
rear calipers with rebuilts twice, burned out pads many times all with no
real effect.

Replaced rusted rear brake lines and that seems to have cured it for one
year then today after a 15 min. drive, I found my left rear caliper
overheating again. Other Right rear brake is fine and never had problem
with front brakes.
The rear caliper overheating only seems to happen in warmer weather.

Any Idea what causes this plaguing rear caliper overheating problem that
sometime melts or burns rubber seals?

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Backyard Mechanic - 27 May 2006 18:32 GMT

> Periodically over last 6 years I have had problems with rear disc
> brakes on 95 Taurus GL 4 dr. sedan with extra weight besides one
[quoted text clipped - 10 lines]
> Any Idea what causes this plaguing rear caliper overheating problem
> that sometime melts or burns rubber seals?

Have had same problem, dry/corroded slide pins.

Replace and lube.

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Yeh, I'm a Krusty old Geezer, putting up with my 'smartass' is the price
you pay..DEAL with it!

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SQUIRE - 28 May 2006 19:41 GMT

>> Periodically over last 6 years I have had problems with rear disc
>> brakes on 95 Taurus GL 4 dr. sedan with extra weight besides one
[quoted text clipped - 14 lines]
>
> Replace and lube.

Thanks guys,

I checked the slide pins. Top was free with lots of lube, but bottom
was dry and almost stuck.

I also found both left and right Emergency brake cables seized solid again,
even though these were replaced 2 years ago. (probably from New England salt
corrosion)

Cleaned and Lubed both pins with silicone , switched places, one pin for the
other. I left seized cables in place.
Drove 130 miles last night with no sign of overheating.

Although this has been an intermittent problem affecting either right or
left caliper, always triggered and spiked much worse by brake heating. So
stuck pin may have done it.

Who sells a good pin kit (and EBrake cables) AND are slide pin holes
(in forged steel caliper mount) known to wear out as well?

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Jason James - 27 May 2006 18:58 GMT

> Periodically over last 6 years I have had problems with rear disc brakes on
> 95 Taurus GL 4 dr. sedan with extra weight besides one driver.
[quoted text clipped - 10 lines]
> Any Idea what causes this plaguing rear caliper overheating problem that
> sometime melts or burns rubber seals?

On mdern cars, the front and rear brake circuits are divided into 2 systems
as far as the mastercylinder design is concerned. This takes the form of :
one cct supplies hydraulic pressure to both front calipers and one rear
wheel, and, the other cct supplies pressure to both front wheels and the
other rear wheel. Going by your symptoms and previous attempted fixes, its
time to look at residual line pressure in the cct which supplies the problem
rear wheel. One way to test the theory is too go for a drive for 10 mins or
so, stop, jack the effected wheel up and test for resistance to turn. If its
virtually locked-up, loosen the bleeder valve and allow a small amount of
hyd-oil to escape. If the wheel is now much freeer,..yu've found the
problem.
Disc-brake design employs *some* residual pressure on purpose to hold the
pad
against the disks to stop accumulation of grit and dirt. Your trouble wheel
must have too much res pressure. Perhaps a resealed MC or a new one will fix
the problem,

Jason

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aarcuda69062 - 27 May 2006 19:14 GMT

> On mdern cars, the front and rear brake circuits are divided into 2 systems
> as far as the mastercylinder design is concerned. This takes the form of :
> one cct supplies hydraulic pressure to both front calipers and one rear
> wheel, and, the other cct supplies pressure to both front wheels and the
> other rear wheel.

Not even close.
It's either FF/RR or FR/FR diagonal

> Going by your symptoms and previous attempted fixes, its
> time to look at residual line pressure in the cct which supplies the problem
[quoted text clipped - 6 lines]
> pad
> against the disks to stop accumulation of grit and dirt.

Disc brakes do not employ residual pressure, drum brakes do.
matter of fact, some disc brake calipers are designed so that the
piston seal pulls the piston back away from the rotor, these
systems will have a quick take-up master cylinder.
As for your logic that it's needed to stop accumulation of dirt,
any dirt would fly off when the rotor is spinning...

> Your trouble wheel
> must have too much res pressure. Perhaps a resealed MC or a new one will fix
> the problem,

Perhaps a collapsed brake hose.

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Jason James - 28 May 2006 00:25 GMT

> > On mdern cars, the front and rear brake circuits are divided into 2 systems
> > as far as the mastercylinder design is concerned. This takes the form of
[quoted text clipped - 5 lines]
> Not even close.
> It's either FF/RR or FR/FR diagonal

That's right,..FR/FR with one rear wheel in each circuit.

> > Going by your symptoms and previous attempted fixes, its
> > time to look at residual line pressure in the cct which supplies the problem
[quoted text clipped - 8 lines]
>
> Disc brakes do not employ residual pressure, drum brakes do.

Drums dont need residual pressure with return springs on the shoes. How many
MCs have you pulled down? Haven't you seen the RP valves (replaceable) in
the line ports?

> matter of fact, some disc brake calipers are designed so that the
> piston seal pulls the piston back away from the rotor, these
> systems will have a quick take-up master cylinder.
> As for your logic that it's needed to stop accumulation of dirt,
> any dirt would fly off when the rotor is spinning...

The centrifugal effect will not stop a stone or chip of gravel from
imbedding itself in a brake pad. Strange ideas,..where did you get them
from?

Jason

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Steve Stone - 28 May 2006 02:35 GMT

I had a rear caliper lock up on me on a Bosch ABS system used in late 1980's
Chrysler products.
I went nuts over the thing, thinking maybe I had problems with brakes hoses
collapsing, or a parking brake issue, or rust in the lines.
After playing with this problem for a few months ( This was my spare old car
used for winter and mall parking lot duty) and sorting thru some
misinformation given to me by a local shop I trusted I found a solution. The
rubber caliper piston seal (not the outer rubber boot, but a rubber ring
between the cylinder and piston) was causing the piston to hang up and not
allow the pads to retract slightly anfter braking, causing overheatig as
described. Again different car, but similar problem ?

Steve

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Jason James - 28 May 2006 03:12 GMT

> I had a rear caliper lock up on me on a Bosch ABS system used in late 1980's
> Chrysler products.
[quoted text clipped - 9 lines]
>
> Steve

Those seals are extremely tight normally, hence the rounded end on the
piston to aid insertion after o/haul, plus "brake grease" in the reco-kit.
I had a '69 Valiant V8 with twin piston calipers which did sieze too. But
that was due to a torn dust-boot admitting water, corroding the piston
(coated steel) and then getting stuck on the seal-ring after they were
G-clamped home to take new pads.

I didn't wish to can the previous poster,..and he may well be right on some
points as one thing that continually changes is brake-technology and design.
When the original poster mentioned frequent maintenance, it followed, I
thought, the slide pins would be OK,..but?

Jason

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