In reply to a message from Pele sent Thu 5 Jul 2012:
What do you mean by ‘brakes do not work’? A soft pedal that
goes to the bottom or a hard pedal but no brakes anyway? Why
did you replace the hose at the rear?
Brakes are a serious matter. IMHO professional knowledge (or
at least a very good DIY mechanic) is needed to service
them! Do you know when it was the last time that the
calipers were serviced or at least inspected? If you ignore
the answer, I would highly recommend you do it NOW, in a car
that is older than 20 years (normally it does not matter how
many miles on the odometer)! I would bet on rust in the
pistons, aged rubber seals and accumulation of dust and
grime in the brake fluid passages. All that being a serious
conspiracy against good working brakes. No easy job yet no
rocket science either, but serious consequences if ignored.–
The original message included these comments:
what could cause brakes to not work when the engine is
running
and work with the engine switched off?
In reply to a message from Luis Gasperini sent Thu 5 Jul 2012:
A soft pedal that goes to the bottom and no braking.
Switch the engine off and the brakes work albeit hard as
there is no power assist.
Hose was replaced because the original was ruptured and
there was no oil in the system at all. So new hose came in
and the system was filled and bled.–
'91 xjs v12 5.3 early facelift in BRG
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In reply to a message from Luis Gasperini sent Thu 5 Jul 2012:
And I forgot to mention that the car is totally dry
underneath no leaks of any kind.
The car has been sitting in a garage for 5 years and we’re
trying to bring it back on the road again.–
'91 xjs v12 5.3 early facelift in BRG
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In reply to a message from Pele sent Thu 5 Jul 2012:
Five years unused??? Do you know the car’s history? Do you
appreciate your life?
Do a complete brake job! Inspect and/or change all discs
(not only wear, cracks too) and pads. You’ll need to drop
the rear cage, but that sounds more complicated than it
really is. Inspect the calipers and replace all rubber
seals. Get the calipers rebuilt if needed and put new
pistons if any of them are rusty. I bet some will be! While
you’re there, put new flexible hoses and a new accumulator
sphere if your ABS system has one. New fluid, purge the air.
If you still have problems, chime again! Maybe I’m too
radical, but… don’t play with the brakes!–
The original message included these comments:
The car has been sitting in a garage for 5 years and we’re
In reply to a message from Luis Gasperini sent Thu 5 Jul 2012:
Don’t forget to inspect or service the parking brake pads.
Most people (with auto-transmission) do not use the parking
brake and though these will have almost no wear, they might
be stuck and lacking service. Very easy with the cage down,
a PITA otherwise.
Now I realise that your car is an early facelift. Maybe it
already has the outside rear brakes and you won’t need to
drop the cage. An additional reason to NOT do this job!–
The original message included these comments:
the rear cage, but that sounds more complicated than it
really is. Inspect the calipers and replace all rubber
It should NOT make any difference if the engine is running or not.
What SHOULD make a difference is whether the ignition key is in the run
position (electric ABS/Booster Pump running) or not. If the fluid
reservoir was empty, and you never bled the fluid intake hose, you
probably have air in the rear brake fluid lines and/or air in the fluid
intake hose, preventing the pump from priming (it’s just sucking air).
Power boost is supplied by the ABS pump. Did you EVER have proper
power boost for the brakes?
You need to review and follow ALL THREE (3) bleed procedures (Front,
Rear, & Fluid Intake Hose) listed in the Jaguar Service Manual, Section
70.25.02
If you don’t have the Jaguar Service Manual, why are you working on
your car without the proper tools?
If you order it from JDHT (~ $25 for Service Manual, Parts Catalogue
and Electrical Guide) let me know, and I can send you some information.
You need to perform the bleed procedures as described in the manual
and then let us know what happens. There are other issues to consider
as well, but first you need to get the air out of the system.
George Balthrop, Clifton, VA USA
89 and 85 XJ-S Coupes; 89 XJ40 VDP-----Original Message-----
From: Pele pele@balorda.com
A soft pedal that goes to the bottom and no braking.
Switch the engine off and the brakes work albeit hard as
there is no power assist.
'91 xjs v12 5.3 early facelift in BRG
In reply to a message from George Balthrop sent Thu 5 Jul 2012:
Whew???
My early cars had little or no braking power. The single band on
the transmission in my T was next to useless. Stomp on all thrree
pedals and distribute the band wear. Not much harder to change
therr than one! Most of us removed the shoes from the rear drums
that ‘‘functioned’’ as a parking brake. Just wore loose and draged
with a rattle.
The rod operated brkes on my A were tons better, but touchy to
adjust and not get a side pull. Way better tha the ‘‘advanced’’ cable
operated ones on some of my other critters, 31 Studebaker
Commander, etc.
Finaly, the 41 Studebaker Champion! Good hydraulic brakes. Anemic
power though. It did not stay around long. Too bad, looked good.
Another story.
But, that was a different era and one could manage by escape
routes, down shifts, etc. No more, a lot more traffic. Higher
speeds. It’s nuts to drive a car with anything less than fully
functioning brakes.
My Jeep has ABS, my Jaguar does not. Different drkive technique
required, yet, I am comfortble with either. As long ago, I learned
that maximum stoppig power is just short of lockup. A four wheel
lockup is not good. A locked wheel does not respond to steering
input.
Carl–
Carl Hutchins 1983 Jaguar XJ6 with LT1 and 1994 Jeep Grand
Walnut Creek, California, United States
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In reply to a message from cadjag sent Sun 8 Jul 2012:
Ok here is a bit of an update:
When the temperature goes slightly above the ‘‘slightly
above the middle’’
city driving mark is when the brakes start failing. So it
has to
do with engine temps. When the temp drops down to the
middle
mark then all is fine.
Nothing chafes, no lines near the exhaust and everything
underneath
is dry, no drips of any kind.
The brakes start failing and the pedal drops all the way
down but still brakes a little bit. Then I pump it a few
times and it ‘‘sort of’’ brakes. Then when I get going
and the temp drops slightly it’s normal again.–
'91 xjs v12 5.3 early facelift in BRG
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In reply to a message from lockheed sent Sat 14 Jul 2012:
Thanks! I like straightforward answers.
One more thing, the car idles at around 1400-1500 rpmi N,
drops down to
1200 in D, with aircon on 1100. So I’m thinking the brakes
anr oil is overheating all the time because the engine
never drops down to 850 and because all the strain I’m
putting on the system having to press the brake pedal at
traffic lights with such a high idle. And the higher
engine temps don’t help.
Ok master brake cylinder it is. Does the fact that this is
an ABS car makes things expensive?–
'91 xjs v12 5.3 early facelift in BRG
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In reply to a message from Pele sent Sat 14 Jul 2012:
The idle problem will be the AAV valve blocked up but often these
can be repaired by a good soaking with carb cleaner and when all
free moving again will cure the idle speed problem.
I would look to see if you can get a repair seal kit for the master
cylinder first. I also had a ford scorpio in 1988 that had the same
brake system and would be perfect except in traffic on a very hot
day only. The fault was no or very little brakes and ABS and Brake
fluid lamps on + ABS pump runs all the time. This after a long time
was traced to a rubber hose from the master cylinder res unit to
input of the pump. The hose collapsed and shut all fluid flow to
pump and so no boost pressure . XJS has a metal pipe but does have
hoses on each end so remember this .–
The original message included these comments:
1200 in D, with aircon on 1100. So I’m thinking the brakes
anr oil is overheating all the time because the engine
never drops down to 850 and because all the strain I’m
putting on the system having to press the brake pedal at
traffic lights with such a high idle. And the higher
In reply to a message from Pele sent Fri 13 Jul 2012:
While all the suggestions are good, I have one question. When
was the brake fluid last changed. Fluid that has absorbed
water can give similar symptoms.–
Maynard 94 XJS V12 Coupe 91XJS(RIP) 86XJ6 78MGB 67MGB
Niles, IL, United States
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In reply to a message from Maynard sent Sun 15 Jul 2012:
4 weeks ago so that’s not it and if that was the problem
wouldn’t the brakes be bad all the time and not just when
the engine gets hot?–
'91 xjs v12 5.3 early facelift in BRG
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Maybe I’m too