[xj] Brake trouble

Fellow listers,
I wonder if anybody out there can help me diagnose my brake problems.
For a while now the pedal on my '76 Series 2 XJ12L will occasionally go
right down to the floor if you held the brake on whilst at traffic
lights etc. Also the “Brake Warning” light would come on intermittantly.

So I ordered a master cylinder overhaul kit and did a very careful and
surgically clean overhaul of the cylinder (my car has the remote
reservoir made by Sovy and a Girling master cyl.).
I re-installed it today and carefully bled the brakes (front only though
as the DPO bust off both bleed nipples on the rear calipers and I’ve yet
to summons the neccessary willpower to drop the rear suspension to get
at the calipers…). Now the pedal has a considerably longer travel than
it used to, the brahe warning light is on all the time except it goes
out briefly when the pedal is halfway through it’s stroke.
The brakes seem to work perfectly well, but it seems as if the primary
pistion in the mastercylinder is not doing it’s job at all even though I
was very careful to install the seals the right way round and to
re-assemble everything properly.
Any ideas?
Thanks in advance

Paddy Glenny

Paddy,

Is the pedal firm or springy when you reached adequate pedal pressure? I
once had a Volvo (essentially the same calipers) that had a bit of spring in
the pedal even after a thorough bleeding. Turned out to be a stuck piston
and the springiness was from the operating piston deflecting the rotor. Jim
Warren

xj12 wrote:> Fellow listers,

I wonder if anybody out there can help me diagnose my brake problems.
For a while now the pedal on my '76 Series 2 XJ12L will occasionally go
right down to the floor if you held the brake on whilst at traffic
lights etc. Also the “Brake Warning” light would come on intermittantly.

So I ordered a master cylinder overhaul kit and did a very careful and
surgically clean overhaul of the cylinder (my car has the remote
reservoir made by Sovy and a Girling master cyl.).
I re-installed it today and carefully bled the brakes (front only though
as the DPO bust off both bleed nipples on the rear calipers and I’ve yet
to summons the neccessary willpower to drop the rear suspension to get
at the calipers…). Now the pedal has a considerably longer travel than
it used to, the brahe warning light is on all the time except it goes
out briefly when the pedal is halfway through it’s stroke.
The brakes seem to work perfectly well, but it seems as if the primary
pistion in the mastercylinder is not doing it’s job at all even though I
was very careful to install the seals the right way round and to
re-assemble everything properly.
Any ideas?
Thanks in advance

Paddy Glenny

Paddy-
I replaced my master cylinder last year on my S2. The Haynes has
directions for resetting the differential pressure switch. The DP switch
will turn your brake warning light on when there is enough of a difference
between the front and rear brake systems. When you bled the brakes, you
triggered the switch. Unfortunately, I don’t have the Haynes here at work,
and the S2 has a different switch that resets itself, so I am only
remembering what I read. Mine is located on the inner fender wall below
the master cylinder, and has both front and rear brake lines running to it.
My recollection is that you have to disconnect it and manually reposition
the plunger. Better check Haynes.
Also, bleed the rears! It is virtually impossible to remove and replace
the master cylinder without getting air into the brake lines. Even if you
managed to prevent the introduction of a bubble, over time the brake fluid
gets grungy and needs to be changed out by bleeding.
I’ve always believed that stopping is more important than going.
Dave
79 XJ6L in drydock for valve job

At 06:04 PM 9/29/1999 -0700, you wrote:>Fellow listers,

I wonder if anybody out there can help me diagnose my brake problems.
For a while now the pedal on my '76 Series 2 XJ12L will occasionally go
right down to the floor if you held the brake on whilst at traffic
lights etc. Also the “Brake Warning” light would come on intermittantly.

So I ordered a master cylinder overhaul kit and did a very careful and
surgically clean overhaul of the cylinder (my car has the remote
reservoir made by Sovy and a Girling master cyl.).
I re-installed it today and carefully bled the brakes (front only though
as the DPO bust off both bleed nipples on the rear calipers and I’ve yet
to summons the neccessary willpower to drop the rear suspension to get
at the calipers…). Now the pedal has a considerably longer travel than
it used to, the brahe warning light is on all the time except it goes
out briefly when the pedal is halfway through it’s stroke.
The brakes seem to work perfectly well, but it seems as if the primary
pistion in the mastercylinder is not doing it’s job at all even though I
was very careful to install the seals the right way round and to
re-assemble everything properly.
Any ideas?
Thanks in advance

Paddy Glenny

Paddy,

I’ve yet to hear one person have any amount of success rebuilding their own
master cylinders, including me. Now, what appears to be a simple mechanical
device is actually subjected to a fair amount of pressures, and my thought
is undetectable scoring, wear, or un-truing of the cylinder is what causes
failure of these devices, appearing as, or in addition to, seal failure. New
seals will not fix the inherent problems in the mating surfaces if they
exist. I have heard (from NAPA guys)that the majority of master cylinders
submitted as cores are not rebuildable without some sort off honing/truing
of the cylinder. Any kind of moisture pitting or dirt particle scoring makes
them virtually useless without machining. Hence the option I take now is to
buy a professionally rebuilt master done by a reputable brake corporation. I
did this with my Jag, a $75.00 no hassle investment from NAPA auto that went
in quick after a bench bleeding session, work perfectly, and 18K miles later
still fabo! I know you spent a fair amount of time, and perhaps brain
damage, rebuilding your master, but I would look seriously at a factory
rebuilt unit as the solution. After all, what’s your time worth, and how
quickly would you like to get you vehicle on the road?

Dennis
1987 XJ6 S3 92K miles-----Original Message-----
From: owner-xj@jag-lovers.org [mailto:owner-xj@jag-lovers.org]On Behalf
Of xj12
Sent: Wednesday, September 29, 1999 6:05 PM
To: xj@jag-lovers.org
Subject: [xj] Brake trouble

Fellow listers,
I wonder if anybody out there can help me diagnose my brake problems.
For a while now the pedal on my '76 Series 2 XJ12L will occasionally go
right down to the floor if you held the brake on whilst at traffic
lights etc. Also the “Brake Warning” light would come on intermittantly.

So I ordered a master cylinder overhaul kit and did a very careful and
surgically clean overhaul of the cylinder (my car has the remote
reservoir made by Sovy and a Girling master cyl.).
I re-installed it today and carefully bled the brakes (front only though
as the DPO bust off both bleed nipples on the rear calipers and I’ve yet
to summons the neccessary willpower to drop the rear suspension to get
at the calipers…). Now the pedal has a considerably longer travel than
it used to, the brahe warning light is on all the time except it goes
out briefly when the pedal is halfway through it’s stroke.
The brakes seem to work perfectly well, but it seems as if the primary
pistion in the mastercylinder is not doing it’s job at all even though I
was very careful to install the seals the right way round and to
re-assemble everything properly.
Any ideas?
Thanks in advance

Paddy Glenny

I just got my series III and took it out for its first drive the
other day. When I was coming down a slight incline I applied the
brakes. At first nothing happened but as I pushed on them harder
the car seemed to slow down a little. I was able to stop the car
but only after a long distance. From what I could tell the rotors
and pads looked alright. (The front ones at least, I didn’t check
the rears yet since I couldn’t see them by just taking the wheels
off)
I’m taking the car to a mechanic soon to have it thoroughly
inspected and would like to have an idea about what is wrong with
the brakes when I go.
The pedal is quite stiff. When I apply normal pressure the pedal
travels about an inch. When I really press hard, it travels a
little furthur and makes a hissing noise like there is air escaping
from somewhere.
Any ideas?
Thanks,
-Will–
85 Black XJ6 VDP
connecticut, United States
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Will, sounds like the master cylinder is leaking or the vacuum line to it from
the manifold is. Don’t drive much!–
Alex
79xj6L SII (BRG + wires)
86xj6 SIII (Black)
61 Sprite MkII (Red)
Menlo Park, Calif.

XJ6exy wrote:

I just got my series III and took it out for its first drive the
other day. When I was coming down a slight incline I applied the
brakes. At first nothing happened but as I pushed on them harder
the car seemed to slow down a little. I was able to stop the car
but only after a long distance. From what I could tell the rotors
and pads looked alright. (The front ones at least, I didn’t check
the rears yet since I couldn’t see them by just taking the wheels
off)
I’m taking the car to a mechanic soon to have it thoroughly
inspected and would like to have an idea about what is wrong with
the brakes when I go.
The pedal is quite stiff. When I apply normal pressure the pedal
travels about an inch. When I really press hard, it travels a
little furthur and makes a hissing noise like there is air escaping
from somewhere.
Any ideas?
Thanks,
-Will

===================================================
The archives and FAQ will answer many queries on the XJ series…
FAQs: http://www.jag-lovers.org/xjlovers/xjfaq/index.html
Archives: http://www.jag-lovers.org/lists/search.html

To remove yourself from this list, go to http://www.jag-lovers.org/cgi-bin/majordomo.

// please trim quoted text to context only

Will, sounds like the master cylinder is leaking or the vacuum line to it
from
the manifold is. Don’t drive much!-----Original Message-----
From: owner-xj@jag-lovers.org [mailto:owner-xj@jag-lovers.org]On Behalf
Of Cannara
Sent: Wednesday, 27 August 2003 2:26 AM
To: xj@jag-lovers.org
Subject: Re: [xj] Brake trouble


Alex
79xj6L SII (BRG + wires)
86xj6 SIII (Black)
61 Sprite MkII (Red)
Menlo Park, Calif.

The pedal is quite stiff. When I apply normal pressure the pedal
travels about an inch. When I really press hard, it travels a
little furthur and makes a hissing noise like there is air escaping
from somewhere.
Any ideas?
Thanks,
-Will

I think you mean the brake servo, Alex. :slight_smile:

Will, try resting your foot on the brake pedal with the engine off and start
'er up. You should feel the pedal go down if the servo is ok. Take a look
under the hood and check the vacuum line, may be a loose connection
otherwise the servo is faulty. Your mechanic will know, brakes on ‘ordinary’
cars work the same way.
Regards,
John Hudson
Brisbane Australia
71 XJ6 SI
85 XJ6 SIII

===================================================
The archives and FAQ will answer many queries on the XJ series…
FAQs: http://www.jag-lovers.org/xjlovers/xjfaq/index.html
Archives: http://www.jag-lovers.org/lists/search.html

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In reply to a message from XJ6exy sent Tue 26 Aug 2003:

Definitely servo not working I recognise the symptoms definitely a
change of underpants situation at the wrong moment! check the non
return valve in the vacuum line to the servo these can get gummed
up & prevent the servo working. Remove & soak in fuel if gummed,
cheaper than a replacement!–
Keith Turner '79 XJ6 based Aristocat, , '81 3.4 XJ6
Swansea, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

===================================================
The archives and FAQ will answer many queries on the XJ series…
FAQs: http://www.jag-lovers.org/xjlovers/xjfaq/index.html
Archives: http://www.jag-lovers.org/lists/search.html

To remove yourself from this list, go to http://www.jag-lovers.org/cgi-bin/majordomo.

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