[xj-s] ABS issues, update

XJ-S
1

Hello all:

A couple of months ago I posted on some observations on the
state of my rear brakes when I remove the IRS for some
extended service work.

to recap:

The passenger side pads were worn to the shoes and the disk
was about half the size of the other side’s disk. Caliper
leaking fluid. The parking brake fork was broken and the
parking brake pads were worn to the point of needing
replacement. Driver’s side looked good.

These brakes had been completely rebuilt (calipers, new
disks, pads, forks, all of it) about 20K mi ago, about 12
years ago.

I concluded, after tearing this down and attempting a
caliper rebuild, that moisture had somehow gotten into the
system and that this had been responsible for the
extraordinary wear (a lister mentioned that the moisture,
as the brakes get hot, vaporizes, and pushes the pads out,
causing premature wear…don’t know if that is really what
happened, but it is certainly plausible given the
observations).

So, yesterday, as part of the last steps in getting the car
back together (many many changes and upgrades done- renew
brakes and hand brakes, 3.54 diff, suspension changes,
incl. addco rear bar, new exhaust system design, bored
throttles, etc., etc.), I bled out the brakes. The rears
produced an incredible amount of white-ish yellow-ish
sludgy slop, and eventually ran clear, indicating that the
system was flushed.

I am guessing that this slop was not only held in the lines
but also in the accumulator and switch, given the volume
that came out. I can also see that this slop probably
contributed to the premature brake pad wear and caliper
condition.

I had not flushed the brake system since that total rebuild
about 10-12 years ago.

After finishing the rears, and moving to the fronts (these
both ran clear from the start), I was working on the last
caliper (driver’s side) when the ABS pump tone changed, and
the pump continued to run. Then, after turning off the
ignition and turning it on again, the pump did not come
on. But, I now have an ABS and brake warning light lit,
and the pedal is high and rock hard.

What fun.

I am strongly suspicious of a brake pressure switch
failure, from the gooey fluid that must have been laying in
that switch body. I pulled the pump assembly and opened
this to examine the internal filter, but this is clean.
Clear fluid. I replaced that switch and the accumulator
when I last rebuilt the brakes.

Lesson learned: flush this system regularly per the manuals!

But, as to the symptoms and root cause: anyone care to
hazard a guess? I am thinking switch right now.

-M–
Mike, 1990 5.3 XJS Conv., 5-speed, SE-ECU, TT Extractors
Lakewood, OH, United States
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2

In reply to a message from mike90 sent Thu 31 Jul 2014:

I think you are correct - the combination pressure switches
do fail.–
lockheed 92 XJS Cpe/97 LT1 Miami FL/ 96 XJS Cv 4.0 Austin TX
Austin, TX, United States
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3

In reply to a message from lockheed sent Fri 1 Aug 2014:

Lockheed:

You were one of the listers I had hoped would respond on
this post.

Thanks; I am going to make some measurements on the switch
later today, but in any case, I have a new switch on order.

I suppose a 10-12 year life is about what one can expect;
perhaps I should also be doing the accumulator as well.

-Mike–
Mike, 1990 5.3 XJS Conv., 5-speed, SE-ECU, TT Extractors
Lakewood, OH, United States
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4

In reply to a message from mike90 sent Fri 1 Aug 2014:

‘‘perhaps I should also be doing the accumulator as well.’’

Good thought if it hasn’t been changed in a number of years.–
lockheed 92 XJS Cpe/97 LT1 Miami FL/ 96 XJS Cv 4.0 Austin TX
Austin, TX, United States
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5

In reply to a message from lockheed sent Sat 2 Aug 2014:

Yep, ordered a new one of those, too.

This sets a record for me on this car: as far as
maintenance goes, the maintenance of the brakes in general
and the ABS in particular have outstripped the costs of
pretty much maintaining everything else, by an
extraordinary margin. Easily 2:1 now, and must be heading
to a larger number with this latest round. Pressure
switches and accumulators aren’t the cheapest parts to be
had. These were first discovered in need of replacement
not long after I got this car (it was about 11 yrs old at
that time, ~75K mi), and the brakes were a mess then, too.

It appears that mileage aside, the pressure switch and
accumulator both have a service life of about 10-12 years,
regardless the mileage.

Still, my take away is: flush this system every two years,
religiously. I will now do this along with my coolant
flush.

The parts I use for this are GM parts, as I have made the
necessary changes to adapt the pressure switch used in
the '89 Buick Reatta (and other cars of that time frame,
those that used the TEVES system). This keeps the price
reasonable. However, I am sure those prices will rise
quite a bit in the next many years as the frequency of use
(e.g., the numbers of cars needing them) goes down.

I should probably consider laying in a set of spares.

-M–
Mike, 1990 5.3 XJS Conv., 5-speed, SE-ECU, TT Extractors
Lakewood, OH, United States
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6

In reply to a message from mike90 sent Sun 3 Aug 2014:

I had a similar problem and I’m happy to see this post. I
have a 94 XJS 4.0L coupe. About a month ago , just after I
had the car inspected the rear brakes burned up during a
normal drive. The rears just started to drag. I had the
brake system flushed when I bought the car but I guess they
didn’t totally clear the system. I just got the rear brakes
changed and we partially flushed the system. I took the car
for a drive and the new brakes are hanging up. I am going
to do a full flush as soon as I can and I hope this
resolves the problem. I really don’t want to replace the
rotors, calipers, hoses, and pads again. I’ll post the
results of my efforts. The fluid was pretty dirty.

Stephen–
dizmando
West Jefferson Hills PA, United States
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7

In reply to a message from mike90 sent Sun 3 Aug 2014:

Consider converting to the Teves IV system. I have had all
the parts and pieces for a while now, and hope to finally
start the project in a month or two.–
lockheed 92 XJS Cpe/97 LT1 Miami FL/ 96 XJS Cv 4.0 Austin TX
Austin, TX, United States
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8

In reply to a message from lockheed sent Sun 3 Aug 2014:

Lockheed:

That’s a good suggestion…what’s involved with this? That
is, are the sensors at each wheel still useable, as well as
the pedal box? I am looking to change the master cylinder
and the pump/accumulator unit only, if possible. I presume
an ECU change would also be required, but that’s fair
enough.

Been thinking of going to the earlier brake system (non
ABS) also, but not quite there yet.

An issue for me will be pedal box compatibility, as mine is
set up for a clutch master and pedal also.

-M–
Mike, 1990 5.3 XJS Conv., 5-speed, SE-ECU, TT Extractors
Lakewood, OH, United States
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9

About a month ago , just after I
had the car inspected the rear brakes burned up during a
normal drive. The rears just started to drag.

Note that, besides the obvious possible causes, this kinda thing can
also be caused by a brake pedal misadjustment. Basically, the pedal
isn’t fully releasing the master cylinder when your foot is off of
it, so the brakes remain slightly engaged – and then as they heat up
and the fluid expands, they become considerably engaged.

At least, that’s the case with regular non-ABS brakes. With the
Teves III system, I dunno how that’d happen without burning up the
FRONT brakes.

– Kirbert

// please trim quoted text to context onlyOn 3 Aug 2014 at 7:05, dizmando wrote:

10

In reply to a message from mike90 sent Mon 4 Aug 2014:

The sensors and wiring are still useable, and a lot of
wiring is eliminated because the ECU is part of the pump
module up front. You will have to change the pedal box, as
the brake pedal arm pivot point is different, and the
mounting for the vacuum booster is not the same as the
mounting for the old MC/Reservoir/Solenoid unit is not the
same. The existing hydraulic lines can be used (minimal
reforming or cutting), or one can form new lines from stock
if desired. If the choice is for non ABS brakes, either an
older pedal box with vacuum booster and MC can be used, or
the newer pedal box with just the vacuum booster and master
cylinder (sans the ABS stuff) can be used.–
lockheed 92 XJS Cpe/97 LT1 Miami FL/ 96 XJS Cv 4.0 Austin TX
Austin, TX, United States
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11

In reply to a message from mike90 sent Mon 4 Aug 2014:

The sensors and lines are compatible and re-useable. The
pedal box will have to be changed since the brake are pivot
point is different as is the mounting of the Vacuum Booster
and the Master cylinder. One can stop at this point and
hook up the hydraulic lines (after removing the old ABS
components) from the wheels to the master cylinder and have
a non ABS system. To do the complete conversion to T4 ABS
involves a bit of yard mining to find some of the parts,
while some are easily found. The existing ABS harness is
opened up, and a great deal of wiring is thrown out, and
the remains are reorganized to serve the T4 system with its
integrated pump/controller module. There is also the choice
of going back to the earlier non ABS pedal box, vacuum
booster, and MC.–
lockheed 92 XJS Cpe/97 LT1 Miami FL/ 96 XJS Cv 4.0 Austin TX
Austin, TX, United States
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12

In reply to a message from mike90 sent Mon 4 Aug 2014:

I’m glad you brought up the brake change over subject, ABS
over to Vacuum booster. The pedal box when converted to a
5sp. dealing with the clutch pedal also what about dealing
with the proportioning valve, auto or 5sp.? I’ve dealt with
these on other car’s, nothing worse than the back brakes
coming on first. I wonder if some type of aftermarket
system is out there.
Larry
91 XJ-S 12cyl 5sp
95 VDP 6cyl–
The original message included these comments:

In reply to a message from lockheed sent Sun 3 Aug 2014:
Lockheed:
That’s a good suggestion…what’s involved with this? That
the pedal box? I am looking to change the master cylinder
An issue for me will be pedal box compatibility, as mine is
set up for a clutch master and pedal also.

–
Larry Hartman
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13

In reply to a message from LarryHartman sent Thu 7 Aug 2014:

Larry:

Agree- switching over braking system must be carefully
considered and executed.

There are the pedal/master assemblies that Tilton offers,
for example, but I have not looked at what is involved in
fitting those. Tilton also offers proportioning valves,
too.

Probably going back to a pre-1989 XJS setup would be
easiest to do; most parts ought to fit and work without
much drama.

-M–
Mike, 1990 5.3 XJS Conv., 5-speed, SE-ECU, TT Extractors
Lakewood, OH, United States
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14

also what about dealing
with the proportioning valve, auto or 5sp.?

My '83 didn’t have a proportioning valve. They are mentioned in the
ROM, but my car only had a simple block where all the brake lines
connected.

How many of us actually have a proportioning valve? Perhaps it’s on
the XJ12 but not the XJ-S? Perhaps it’s in some markets but not
others? Perhaps some model years but not others?

I’ve dealt with
these on other car’s, nothing worse than the back brakes
coming on first. I wonder if some type of aftermarket
system is out there.

Well, lots of cars have proportioning valves, so I suppose you could
retrofit one. Not sure what benefit you’d expect, though.

I dunno if it’s always true, but one explanation I got for a
proportioning valve was to deliberately bring the rear brakes on
first when pedal force is light, such as when driving on snow or ice.
When the brakes are applied harder, the fronts take over and become
much stronger than the rears. If you establish the front/rear
proportion with cylinder diameters or with a tandem master cylinder
setup, the proportion is fixed – the same at light braking or heavy
braking. I guess this is considered a bad thing in snow and ice, but
I’m from Florida and wouldn’t know.

– Kirbert

// please trim quoted text to context onlyOn 7 Aug 2014 at 6:39, LarryHartman wrote:

15

In reply to a message from Kirbert sent Thu 7 Aug 2014:

I know that the wife’s '89, '92, and '96 all had/have one.
Jaguar calls it a ‘‘pressure conscious reduction valve’’.–
lockheed 92 XJS Cpe/97 LT1 Miami FL/ 96 XJS Cv 4.0 Austin TX
Austin, TX, United States
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16

In reply to a message from mike90 sent Thu 7 Aug 2014:

When, not if, my ABS goes I’m going to look into this system
called ‘‘Hydroboost’’. I read about it in Car Craft mag. March
2009 issue, yes a while back. It’s to much to explain here
on the workings. It works with a Wildwood master cyl.I
think.Its probably expensive, but ever price a new Jaguar
ABS master cyl.? Anyway, trying to change and adapted the
pre ABS to a stock Vac boost Jag system to a after market
manual kit pedal box could be challenging but probably doable.
Larry
91 XJ-S 12cyl 5sp
95 VDP 6cyl–
The original message included these comments:

Agree- switching over braking system must be carefully
considered and executed.
Probably going back to a pre-1989 XJS setup would be
easiest to do; most parts ought to fit and work without
much drama.

–
Larry Hartman
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17

In reply to a message from LarryHartman sent Sat 9 Aug 2014:

‘‘Its probably expensive, but ever price a new Jaguar
ABS master cyl.?’’

Yes, for the Teves IV, a rebuilt master cylinder is $90.00

  • about a $22.00 core charge, which is refundable when you
    return your old core to them. A new master cylinder is
    $490.00. Same master cylinder as your Vanden Plas. Check
    Rock Auto and others!!–
    lockheed 92 XJS Cpe/97 LT1 Miami FL/ 96 XJS Cv 4.0 Austin TX
    Austin, TX, United States
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18

In reply to a message from lockheed sent Sat 9 Aug 2014:

I don’t know any price on any master cylinder (MC) new or
rebuilt, at this time. All I know is what I was told a few
years back, when the ‘‘DIRECT’’ replacement MC for a 1991 XJ-S
with ABS brakes was NOT available from ANYBODY but a Jaguar
dealer, new only! List price $3000!! Today Rock Auto or
someone else maybe putting out a ‘‘rebuilt direct
replacement’’ MC’s for the 91 XJ-S with ABS, I don’t know!
With that said, my understanding changing a 91 with ABS
‘‘AND with the aftermarket 5speed manual’’ over to an earlier
vac boost is not a bolt in deal when dealing with the pedal
box supplied with the stock ABS equipped 91 manual kit.
So ‘‘I’m assuming’’ the easiest, way to change to the vacuum
boost system is with a pedal box from a pre ABS year XJ-S
that is part of the manual aftermarket kit OR are you saying
the Teves IV vac booster & MC is compatible (bolt in) with a
manual kit pedal box supplied by the manual kit company for
an ABS car that I want to change over ?
Larry
91 XJ-S 12cyl 5sp
95 VDP 6cyl–
The original message included these comments:

‘‘Its probably expensive, but ever price a new Jaguar
ABS master cyl.?’’
Yes, for the Teves IV, a rebuilt master cylinder is $90.00
$490.00. Same master cylinder as your Vanden Plas. Check
Rock Auto and others!!

–
Larry Hartman
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19

In reply to a message from LarryHartman sent Sun 10 Aug 2014:

Larry,
I don’t have an answer for that. I don’t know if any of the
XJ’s had a manual pedal box in conjunction with the Teves
IV ABS system. Further, if one did, I don’t know that the
pedal box with brake and clutch pedals (from an XJ) would
bolt into a XJS - I think the firewall angles are different.–
lockheed 92 XJS Cpe/97 LT1 Miami FL/ 96 XJS Cv 4.0 Austin TX
Austin, TX, United States
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20

I don’t know if any of the
XJ’s had a manual pedal box in conjunction with the Teves
IV ABS system.

Jaguar did offer 6-bangers with manual transmission, but I dunno if
they kept it up long enough to get a Teves IV ABS system. Even if
they had, probably a pretty rare combination.

Further, if one did, I don’t know that the
pedal box with brake and clutch pedals (from an XJ) would
bolt into a XJS - I think the firewall angles are different.

It’s well known that the pedal box from an XJ will NOT interchange
with the pedal box from an XJ-S. The only chance there would be if
Jaguar/Ford revised the XJ soooo much in the mid 90’s that it
suddenly became interchangeable – but I’d bet against it.

The Teves IV requires virtually the same pedal box as the pre-ABS
cars (and totally different than the Teves III). However, the Teves
IV pedal box is plastic while the pre-ABS pedal box is cast aluminum.
If you’re gonna modify an XJ-S pedal box to add a clutch pedal, you
might be better off starting with the pre-ABS box, which you can weld
on.

– Kirbert

// please trim quoted text to context onlyOn 10 Aug 2014 at 10:08, lockheed wrote: