The latest drive we took with the 1994 XJS came to a sudden halt when
smoke started coming out from under the rear of the car. After stopping and
checking under the car, it became apparent that the brake discs were
dragging. The calipers were not fully releasing. A careful and slow drive home
allowed the car to be safely placed in the garage. I expected to find a
collapsed flex hose prior to the rear split since the discs on both sides were
dragging. I was surprised to find no flex hose. Is it possible both outer
flex hoses in the rear decided to collapse at the same time? What’s the
probability of that.
While I was looking at the lines, I saw the pressure reducing valve on the
rear brake line under the power steering reservoir was leaking a bit.
Could this be the source of both rear calipers not fully releasing? If so, is
there a kit available for the valve or is a new valve required? I noticed
the external O-ring appears to be failing. It’s not gripping the valve
and can be easily slid out of the groove and off the valve. The poor
condition of this O-ring is why I’m thinking a parts kit may be needed.
If I have to pull the line apart that goes to the rear brakes, I may as
well go ahead and replace both rear flex lines. The ones on the car are
probably the originals.
Am I considering the right solutions or is there something else I should
look at?
Thanks,
Dave
1994 XJS 2 + 2 Convertible
1969 E Type
The proportioning (pressure delay) valve is due for
replacement.
Steven (aka dizmando) reported this very same problem not
long ago.
Be careful – there are two part numbers and they are not
interchangeable
Your is likely the expensive CBC4233.
The one you don’t need is MHF5818AB (cheaper and easier to
source)
Look these numbers in the archives for more info.
Steve–
The original message included these comments:
The latest drive we took with the 1994 XJS came to a sudden halt when
smoke started coming out from under the rear of the car. After stopping and
checking under the car, it became apparent that the brake discs were
dragging. The calipers were not fully releasing. A careful and slow drive home
allowed the car to be safely placed in the garage. I expected to find a
collapsed flex hose prior to the rear split since the discs on both sides were
dragging. I was surprised to find no flex hose. Is it possible both outer
flex hoses in the rear decided to collapse at the same time? What’s the
probability of that.
While I was looking at the lines, I saw the pressure reducing valve on the
rear brake line under the power steering reservoir was leaking a bit.
In reply to a message from sbobev sent Fri 2 Oct 2015:
Dave,
Without wishing to disabuse you of the notion that it might be
the valve, have you considered that you might not have
released the handbrake (or that it might be stuck)?
I’ve seen a number of XJS with stuck rear outboard brakes that
proved to be the handbrake.
I did go through this not long ago. I have a brand new
more expensive proportioning sitting on my desk. I ended up
using a proportioning valve from my 89 parts car which was
the cheaper of the two. When I researched the part at
Jaguar heritage it showed that I needed the more expensive
valve. If you need the more expensive valve contact me off
list and I’ll make you a deal you won’t be able to refuse.
I’d love to get it off my desk. If you do a forum search I
left a lot of information on the situation.
In reply to a message from ptjs1 sent Sat 3 Oct 2015:
With a '94, it should be easy enough to determine this, no?
(e.g., whether the calipers are locking on the hydraulic
side, or on the handbrake side, that is) doesn’t this year
have the outboard disks?
In reply to a message from mike90 sent Sun 4 Oct 2015:
Mike,
It should be possible to determine if it’s the caliper pads
that are jammed or the internal handbrake shoes. However, the
problem arises that if the disc heats up a lot due to
handbrake show friction, it can also cause the normal caliper
pads to then stick to the disc giving a conflicting symptom.
In reply to a message from mike90 sent Sun 4 Oct 2015:
‘‘whether the calipers are locking on the hydraulic side, or on the
handbrake side, that is) doesn’t this year have the outboard
disks?’’
Can’t happen (Outboard Brakes)- the hydraulic calipers operate on
the disk, and the mechanical handbrake operates brake shoes on the
inside of the disk hub- same as the design used on the C3 Corvette
rear brakes from the late 60’s thru 1982.–
lockheed 92 XJS Cpe/97 LT1/4L60E Miami FL
Austin, TX, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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Steve,
Thanks much for the advice. I was afraid this would be the case. I’ve
ordered a replacement valve CBC4233 and two flex hoses. I may not need the
replacement hoses but it seems like a good time to go ahead and replace the
old ones.
David
'94 XJS Convertible
'69 E-Type
In a message dated 10/3/2015 7:56:17 A.M. Central Daylight Time, owner-xj-s-digest@jag-lovers.org writes:Date: Fri, 2 Oct 2015 18:25:47 -0700
From: “sbobev” shelxtl@yahoo.com
Subject: Re: [xj-s] Rear brake calipers not fully releasing
In reply to a message from @DReinke750 sent Fri 2 Oct 2015:
The proportioning (pressure delay) valve is due for
replacement.
Steven (aka dizmando) reported this very same problem not
long ago.
Be careful – there are two part numbers and they are not
interchangeable
Your is likely the expensive CBC4233.
The one you don’t need is MHF5818AB (cheaper and easier to
source)
Paul,
That’s a very good point regarding the handbrake. I have failed to
release the handbrake in the past - before I converted the small warning lights
to LED’s. Now they’re bright enough that they’re noticed. The handbrake
hasn’t been left on for many months.
I should know if the valve and flex pipe replacement solves the problem in
a week or so when the parts arrive and I replace the old items.
Cheers,
David
'94 XJS Convertible
'69 E-Type
In a message dated 10/4/2015 9:37:33 A.M. Central Daylight Time, owner-xj-s-digest@jag-lovers.org writes:Date: Sat, 3 Oct 2015 08:58:59 -0700
From: “ptjs1” p.sinnott@btopenworld.com
Subject: Re: [xj-s] Rear brake calipers not fully releasing
In reply to a message from sbobev sent Fri 2 Oct 2015:
Dave,
Without wishing to disabuse you of the notion that it might be
the valve, have you considered that you might not have
released the handbrake (or that it might be stuck)?
I’ve seen a number of XJS with stuck rear outboard brakes that
proved to be the handbrake.
Good luck
PAul
// please trim quoted text to context only
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
10
Can’t happen (Outboard Brakes)- the hydraulic calipers operate on the
disk, and the mechanical handbrake operates brake shoes on the inside
of the disk hub…
If the hydraulic calipers are binding, it could be the calipers
themselves, the flex lines leading to them, or the master cylinder.
If it’s the calipers themselves or the flex lines, you’d normally
expect that only one brake was binding; unlikely both sides would
fail simultaneously. If both sides are bound up, I’d be looking at
the master cylinder – or the proportioning valve, if the car has
one.
– Kirbert
// please trim quoted text to context onlyOn 4 Oct 2015 at 17:32, lockheed wrote:
A couple weeks ago I mentioned that I had problems with the
back brakes not releasing. The suggestion was to replace the
proportioning valve, or whatever the thing is called that
controls the pressure going to the back brakes. I received the
replacement and after installing it and bleeding the brakes, I
took the car for a drive. The following happened:
The brake warning light randomly came on, stayed on for a short
while and then went out. This happened a number of times on a
20 mile drive. I also noticed the transmission shifting
harshly. The transmission issue had never occurred before but
am at a loss how the two issues could be related. Toward the
end of the drive, the transmission quit shifting altogether.
It stayed in top gear unless I stopped and shifted into
reverse. When I shifted back into drive, it immediately went
into top gear. It appears it�s in limp home mode. My question
is what could have happened? Coincidence?
How do I go about finding the transmission fault codes? Once I
find the fault code, does anyone have a list that explains what
the codes mean? Can I reset everything and start over?
Thanks again in advance.
Dave
94 2+2 4.0 Convertible–
Dave Reinke, 69 E-Type 2+2, 94 XJS 4.0 Convertible
Camdenton,MO, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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In reply to a message from Dave Reinke sent Thu 15 Oct 2015:
Hi Dave:
After replacing the pressure delay valve, are the rear
calipers still binding or not?
The transmission issue should not be related to the brakes.
The 4L80e codes can be read w/o a scanner, I don’t know
about the ZF. Probably you can reset by disconnecting the
battery power and see if the lip home mode will come back…
Steve
PS Were the brakes bled properly? The brake warning light
coming one suggest something is amiss–
The original message included these comments:
A couple weeks ago I mentioned that I had problems with the
back brakes not releasing. The suggestion was to replace the
proportioning valve, or whatever the thing is called that
controls the pressure going to the back brakes. I received the
replacement and after installing it and bleeding the brakes, I
took the car for a drive. The following happened:
The brake warning light randomly came on, stayed on for a short
while and then went out. This happened a number of times on a
20 mile drive. I also noticed the transmission shifting
harshly. The transmission issue had never occurred before but
am at a loss how the two issues could be related. Toward the
In reply to a message from sbobev sent Thu 15 Oct 2015:
The brakes are working just fine. No smoke f rom the back
brakes. Hard stops resulted in the ABS working. The light did
not come on for the last few miles of the drive. I’m wondering
if I failed to get some air out of the lines when I replaced
the proportioning valve.
I bled the brakes per the shop manual. It was a two person job
with my wife pressing the brake pedal and turning the key on
while I was in back opening and closing the bleed screw.
Tedious but not difficult.
I would like to know for sure if I can ground terminal A8 in
the trunk and read codes by watching the transmission warning
light blink. Does this work for the ZF tranny? Alternatively I
will disconnect the battery to reset everything and see what
happens.–
The original message included these comments:
After replacing the pressure delay valve, are the rear
calipers still binding or not?
In reply to a message from Dave Reinke sent Thu 15 Oct 2015:
Dave:
Give it a try. After a re-boot, the TCM could work just
fine.
The TEVES is tricky to bleed properly. You did the back,
but did you do the front?
Did you bleed the line from the reservoir to the ABS
pump/accumulator assembly? This was the 1st step in the
procedure.
When I got my car, the red warning light for the brakes
would come periodically, after some hard(er) braking. This
was an early sign of the accumulator ball on its way out –
it has not happened since I replaced it.
How old is yours?
Steve–
The original message included these comments:
I would like to know for sure if I can ground terminal A8 in
the trunk and read codes by watching the transmission warning
light blink. Does this work for the ZF tranny? Alternatively I
will disconnect the battery to reset everything and see what
In reply to a message from sbobev sent Fri 16 Oct 2015:
Well, the reboot didn’t change anything. The transmission
warning light is still on and the brake light still comes on at
random times.
In response to questions, I only bled the back lines and did
that per the shop manual instructions. I guess I need to do a
complete brake bleed. I’m just curious what the front lines
would have to do with the issue since the only line I opened
was the one going to the back brakes.
Is there a better bleed procedure other than the one in the
shop manual?
I will also locate the TCM relay and try to read the
transmission fault codes after grounding terminal A8. Does
anyone have a listing of the fault codes and what they mean? I
could really use the list.
Looks like a good weekend project.
Cheers,
Dave
94 XJS 2+2 4.0 Convertible.–
The original message included these comments:
In reply to a message from Dave Reinke sent Thu 15 Oct 2015:
Dave:
Give it a try. After a re-boot, the TCM could work just
fine.
The TEVES is tricky to bleed properly. You did the back,
but did you do the front?
In reply to a message from sbobev sent Fri 16 Oct 2015:
Well, the reboot didn’t change anything. The transmission
warning light is still on and the brake light still comes on at
random times.
In response to questions, I only bled the back lines and did
that per the shop manual instructions. I guess I need to do a
complete brake bleed. I’m just curious what the front lines
would have to do with the issue since the only line I opened
was the one going to the back brakes.
Is there a better bleed procedure other than the one in the
shop manual?
I will also locate the TCM relay and try to read the
transmission fault codes after grounding terminal A8. Does
anyone have a listing of the fault codes and what they mean? I
could really use the list.
Looks like a good weekend project.
Cheers,
Dave
94 XJS 2+2 4.0 Convertible.–
The original message included these comments:
In reply to a message from Dave Reinke sent Thu 15 Oct 2015:
Dave:
Give it a try. After a re-boot, the TCM could work just
fine.
The TEVES is tricky to bleed properly. You did the back,
but did you do the front?
In reply to a message from Dave Reinke sent Mon 19 Oct 2015:
With regard to the random red brake light, how long has it been
since you changed your brake accumulator ball atop the pump???–
lockheed 92 XJS Cpe/97 LT1/4L60E Miami FL
Austin, TX, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –
In reply to a message from lockheed sent Mon 19 Oct 2015:
I’ve owned the car for 4 years and have not changed the
accumulator ball. When I start the car after sitting for an
extended period of time, the light goes out as it always has. I
don’t understand how the accumulator ball would become a problem
at the same time I replace the proportioning valve but then
anything is possible with these cars.–
The original message included these comments:
In reply to a message from Dave Reinke sent Mon 19 Oct 2015:
With regard to the random red brake light, how long has it been
since you changed your brake accumulator ball atop the pump???
In reply to a message from Dave Reinke sent Mon 19 Oct 2015:
I had a similar problem recently with my rear brakes after re
refitting the pedal box, during my conversion to a 5 speed ma
manual.
I had inadvertently overtightened the pivot bolt for the
brake pedal. Symptoms were hot rear brakes, For what ever
reason I was looking at the brake pedal in the cabin and pulled b
pulled back on it and it came up a few millimeters to hit it’s res
it’s rest. Every time I pressed the brake pedal when testing
testing or driving, the pedal was not returning to it’s rest, bu
rest, but staying engaged enough to cause the rear brakes to work,
to work, but not the fronts.
I loosened the brake pivot bolt half a turn (in the engine bay) a
bay) and this allowed the pedal to have full travel and the proble
problem disappeared.
The amount of extra travel was minimal and was not obvious by
by just looking at the pedal.
In reply to a message from Dave Reinke sent Mon 19 Oct 2015:
The weekend has started and I found myself bleeding the brakes
one more time. This time I did it all and used a couple quarts
of fluid. Took the car for a drive and no more random brake
warning light. Brakes appear to be functioning fine. That;s
the good part. I found the transmission power relay but have
not found anything that is called a TCM relay. I found the TCM
itself. It’s just to the right of the convertible hydraulics.
Where is the A8 terminal I’ve been told I need to ground to
see what fault codes are stored?
I did try the suggestion and disconnected the battery to rest
the codes. No luck there. When I reconnected the battery, the
transmission warning light stayed on and the transmission does
not shift. I have one forward gear. Grrrrr!!!
To make matters worse, the failed bulb warning is now on and I
checked that all the lights are working. I’m beginning to
think the car hates me.
Anyone have any ideas regarding the transmission faults, how to
read them and once I do read them, what the codes mean.
Since the brake issue seems to be solved, should I start a new
thread for the transmission issue?
Cheers,
Dave
1994 4.0 Convertible–
The original message included these comments:
I will also locate the TCM relay and try to read the
transmission fault codes after grounding terminal A8. Does
anyone have a listing of the fault codes and what they mean? I
could really use the list.
