Hi gents…did I read a blog that indicated that momentary flash of
brake light at times when applying fast or hard braking is normal?
If not then any suggestion on what issue may be? Fashs occurs only
sometimes and only when I hit brakes fast for a hard stop. Fluid
level is fine…brakes pads are fine.
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Hi Howard.
Always good to include the model and year of Jag in your sign off line.
Do you mean a flash of the rear lights or the warning light on the dash?
Regards
Robin
Auckland NZ----- Original Message -----
From: “HMS” hms200@hotmail.com
To: xj40@jag-lovers.org
Sent: Saturday, June 27, 2009 6:36 PM
Subject: [xj40] 93 XJ6 Dash Brake Light flashes
Hi gents…did I read a blog that indicated that momentary flash of
brake light at times when applying fast or hard braking is normal?
If not then any suggestion on what issue may be? Fashs occurs only
sometimes and only when I hit brakes fast for a hard stop. Fluid
level is fine…brakes pads are fine.
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In reply to a message from HMS sent Fri 26 Jun 2009:
Howard,
If the ‘BRAKE’ warning light appears, it is due to one (or
more) of three things -
a) Pad wear sensor open circuit or grounded
b) Low brake boost pressure
c) Low brake fluid level in reservoir
If when the ‘BRAKE’ warning is illuminated you can press the
VCM button, you should see either ‘PAD’ if a) or ‘FAIL’ if
b) or c)
The usual problem in the circumstances you describe is that
the flying lead from the left front or right rear pad wear
sensor is being snagged by the ragged edge on the
circumference of a worn disc as the caliper moves when you
apply the brake and momentarily the pad wear sensor lead
conductor wire is grounded on the disc through torn
insulation to flash the warning light.
Check the security of the pad wear sensors in the notches in
the inboard pads on the left front and right rear brakes and
the routing of the flying leads to ensure that they remain
clear of the discs.–
The original message included these comments:
Hi gents…did I read a blog that indicated that momentary flash of
brake light at times when applying fast or hard braking is normal?
If not then any suggestion on what issue may be? Fashs occurs only
sometimes and only when I hit brakes fast for a hard stop. Fluid
level is fine…brakes pads are fine.
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In reply to a message from HMS sent Fri 26 Jun 2009:
I had similar thing a while ago and it steadily got worse until the
brake light came on every time I hit the brakes. I had changed the
front pads and sensors and still had the problem. Eventually I
realised that the rear brakes had sensors on them as well. Changed
them and problem solved.
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In reply to a message from Bryan N sent Sat 27 Jun 2009:
I am having the same problem but coupled with the flash there is a
regular clicking sound when the brake pedal is depressed and
continuously while the ignition is turned on. The brake light flash
could be a warning that ABS is no longer functioning but brakes are
still working? !1990 sovereign–
mgbgt
Calgary, Alberta, Canada
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In reply to a message from 1968roadster sent Sat 27 Jun 2009:
I think that in your case, the problem is a lack of brake
accumulator pressure - the clicking you hear is in all
probability the ABS pump relay energising repeatedly to
start the pump to top up the accumulator.
If you get the chance when the ‘BRAKE’ light is on, press
the VCM button and you will probably see ‘FAIL’ on the LCD
display.
Try this check.
First, with the ignition ‘OFF’, pump the brake pedal 20 +
times to exhaust the accumulator.
Turn on the ignition to position (I) - the ‘accessory’
position - and listen for the Teves pump to stop, indicating
that the accumulator is (theoretically) fully charged.
Turn the key to ‘OFF’ and operate the brake pedal until the
pedal ‘goes hard’ - i.e. you no longer have any brake boost.
How many brake applications do you get before the pedal
‘goes hard’ ?
Anything below 20 + applications of the brake before that
happens suggests that the accumulator is failing.
When the accumulator has lost its charge, not only will the
brake boost be lost but the ABS system will disengage - but
the brakes themselves will still work - albeit with less
effect and requiring greater foot pressure.–
The original message included these comments:
I am having the same problem but coupled with the flash there is a
regular clicking sound when the brake pedal is depressed and
continuously while the ignition is turned on. The brake light flash
could be a warning that ABS is no longer functioning but brakes are
still working? !1990 sovereign
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In reply to a message from Bryan N sent Sat 27 Jun 2009:
Hey thx to all for your responses thus far…also took advice on
signature.
Ok so here’s what’s now happening…
I attempted your test Bryan and did get some results, though not
exactly what I expected. Issue got worse actually and moved more
toward the A) B) C) test.
Went thru the pump down ignition off/on test with no
surprises…short flash with ignition. After a few cycles of this
I started noticing that going thru that cycle the light started
staying on steady until I could hear to pump stop. While ‘‘Brake’’
light is on the display does show ‘‘FAIL’’ when I press ACM.
All four rotors are brand new, all pads are like new and fluid
level is ok. So does this sound like accumulator failure as
suggested could be an option? If yes then do I need to replace
just the sphere? The pump sounds fine I suppose…it definitely
runs and goes on/off as it should I think from what I can hear. I
suppose all would strongly recommend new rather than chancing a
used one off eBay, right? The Sphere contains a standby
pressurized fluid chamber with a diaphram to hold the pressure,
yes? Failure of accumulator translates to diaphram failure within
the sphere?
Your test procedure Bryan with the 20+ brake apply (etc) I couldn’t
really understand vs. results I was getting, but maybe that’s
because of the faulure symptoms I’m getting? My pedal goes hard
after 1-2 applications of brake. With the above described
worsening of issue now…I start engine and apply brakes (brake
light on steady now for about a second when brake applied) with
more pedal play…I hold it hard and do feel it push back at me a
bit and then hold after I apply full brake pressure.
Accessory on - Apply brakes
Brake light on ~1 sec
ACM displays ‘‘FAIL’’ while brake light is on
Pump runs ~2 sec. then stops…no ACM failure display
Pedal play mush and does push back as pressure builds
Engine running - Apply brakes
Brake light on ~1 sec
ACM displays ‘‘FAIL’’ while brake light is on
Cannot hear pump
Pedal play mush and does push back as pressure builds
(Appears to be same symptoms with or without engine running)
I’m stumped…but I’m guessing all this info may scream out to all
of you long standing Jag owners with a cause…failed or failing
accumulator really? :)–
Howard - 93 Vanden Plas 4.0L
Honolulu, HI, United States
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In reply to a message from HMS sent Sat 27 Jun 2009:
Yes, certainly sounds as if your accumulator is on its way
out - or gone already.
I would not bother with a used accumulator - always fit new
so that you are sure it is good.
You can pretty much tell if the accumulator has lost its
nitrogen charge once you have removed it. If you stick a
blunt probe in the oil orifice, if the accumulator still has
a good nitrogen charge, the probe will not enter the orifice
beyond the start of the sphere because the diaphragm will be
forced down by the nitrogen pressure behind it to block the
hole. If the probe enters the sphere up to half way or
beyond, the nitrogen charge is spent and the accumulator
needs replacing.–
The original message included these comments:
level is ok. So does this sound like accumulator failure as
suggested could be an option? If yes then do I need to replace
just the sphere? The pump sounds fine I suppose…it definitely
runs and goes on/off as it should I think from what I can hear. I
suppose all would strongly recommend new rather than chancing a
used one off eBay, right? The Sphere contains a standby
pressurized fluid chamber with a diaphram to hold the pressure,
yes? Failure of accumulator translates to diaphram failure within
the sphere?
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In reply to a message from Bryan N sent Sat 27 Jun 2009:
Ok thx Bryan…
So is there anything magic on replacing? Do I need to disconnect
anything, relieve pressure in any way before unscrewing the sphere,
bleed system after replacement? I’ll look for instructions but
would welcome your very informed tips.
Hey also…is this now a more likely culpret as well for my still
illusive ‘‘ABS Light is on constant’’ issue that so far is still
unresolved? I secured a full set of good condition speed sensors
(I ohm metered each one) and am planning to ohm test each installed
sensor this weekend and replace as may be required.–
Howard - '93 Vanden Plas 4.0L
Honolulu, HI, United States
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In reply to a message from HMS sent Sat 27 Jun 2009:
Hey Bryan…additional thought…
Can I safely perform the sphere test (probe) you described now and
be able to reinstall it safely until my new one arrives? I’m a
curious sort and if that will more definitively confirm the bad
sphere before I shell out $200 for a ‘‘new’’ replacement then I’d
sure like to do so. What do you think?–
Howard - '93 Vanden Plas 4.0L
Honolulu, HI, United States
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In reply to a message from HMS sent Sat 27 Jun 2009:
Howard,
If the cause of the ABS warning light being permanently on
after the Teves pump stops after you first switch on the
ignition is only due to the accumulator failure, the
‘BRAKE’ warning light would remain permanently on too.
Since you also had a speedo failure I suspect you still have
another ABS fault (as well perhaps) which that ABS ‘blink
test’ I posted in your other thread would identify.
Replacing the Teves accumulator is no big deal. You need to
de-pressurise the system by pumping the brake pedal hard 20
times and you will need a strap wrench to unscrew the
sphere and a large pipe wrench to hold the base to stop it
being twisted and ruining the rubber mounts. The sphere has
an Allen key hexagon in the top, but you won’t undo it using
that - its is too tight. However, when replacing the sphere,
it only needs to be snugged down on to the ‘O’ ring seal,
definitely NOT over-tightened.
Obviously you need to protect the paintwork in the area
around and under the accumulator / motor unit with lots of
old rags to prevent damage from any drips of brake fluid.–
The original message included these comments:
So is there anything magic on replacing? Do I need to disconnect
anything, relieve pressure in any way before unscrewing the sphere,
bleed system after replacement? I’ll look for instructions but
would welcome your very informed tips.
Hey also…is this now a more likely culpret as well for my still
illusive ‘‘ABS Light is on constant’’ issue that so far is still
unresolved? I secured a full set of good condition speed sensors
(I ohm metered each one) and am planning to ohm test each installed
sensor this weekend and replace as may be required.
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In reply to a message from HMS sent Sat 27 Jun 2009:
Howard,
You can safely check out the accumulator with a blunt
probe as I described and re-install it (with a new ‘O’ ring)
if satisfactory.–
The original message included these comments:
Can I safely perform the sphere test (probe) you described now and
be able to reinstall it safely until my new one arrives? I’m a
curious sort and if that will more definitively confirm the bad
sphere before I shell out $200 for a ‘‘new’’ replacement then I’d
sure like to do so. What do you think?
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In reply to a message from Bryan N sent Sat 27 Jun 2009:
Bryan…you rock buddy!! Where did you get all this knowledge?
Yes, I plan to do the blink test today and correct that my speedo
is still dead. I snagged a full set of ‘‘used’’ sensors for the
right price so I decided to wait until I had them in hand
first…they just arrived…all in good shape and all pulled a good
ohm test. All four of my current sensors are in very sad shape so
nothing would surprise me there…insulation all cracked and 3 or 4
even had the metal shrouding shreaded under the rubber insulation.
The inside wires did look intact however. As I said before, I did
apply a lame attempt to repair them with electrical tape but didn’t
hold any great hopes…but hey, I had the tape but no new sensors
so decided I’d give it a whirl…lameeee…no change.
Ok…so I will blink test and then replace. I will also order new
sphere.
Trying to get all these darn kinks out of this great vehicle so I
can ship it to my daughter in Colorado as a gift…then on to my
next great project. :)–
Howard - '93 Vanden Plas 4.0L
Honolulu, HI, United States
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In reply to a message from HMS sent Sat 27 Jun 2009:
Howard,
When you fit the replacement ABS wheel sensors, smear the
outside surface with anti-seize compound (copper grease is
good) so that they don’t ‘weld’ themselves to the hub carrier.–
The original message included these comments:
is still dead. I snagged a full set of ‘‘used’’ sensors for the
right price so I decided to wait until I had them in hand
first…they just arrived…all in good shape and all pulled a good
ohm test. All four of my current sensors are in very sad shape so
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In reply to a message from HMS sent Sat 27 Jun 2009:
FYI - Bryan has been our helpful XJ40 ‘‘man in the know’’ for a long
time on JLers … He’s much appreciated by all here … &:-)–
The original message included these comments:
Bryan…you rock buddy!! Where did you get all this knowledge?
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In reply to a message from AttyDallas sent Sun 28 Jun 2009:
Bryan and/or others…
In sourcing a replacement ABS Accumulator sphere I am finding after-
market replacements that tout being compatible with Jag’s,
Cadillac, Chrysler, etc…other vehicles with Teves ABS. The after-
market is considerable less costly. It is slightly different in
appearance (doesn’t have the allen wrench neck) but looks the same
overall.
Anybody gone this route? Is there a concensus on this…stay with
Jag part # JLM 1907 new or safely go after-market new?–
Howard - '93 Vanden Plas 4.0L
Honolulu, HI, United States
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In reply to a message from HMS sent Sun 28 Jun 2009:
Howard,
The Accumulator you want is under the AC Delco part number
25528382 - it is the one fitted to the Buick Reatta amongst
others. It is identical to the Jag unit - made in Germany.
Unfortunately, AC Delco Direct are out of stock because they
used to be the cheapest! :-(–
The original message included these comments:
In sourcing a replacement ABS Accumulator sphere I am finding after-
market replacements that tout being compatible with Jag’s,
Cadillac, Chrysler, etc…other vehicles with Teves ABS. The after-
market is considerable less costly. It is slightly different in
appearance (doesn’t have the allen wrench neck) but looks the same
overall.
Anybody gone this route? Is there a concensus on this…stay with
Jag part # JLM 1907 new or safely go after-market new?
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In reply to a message from Bryan N sent Sun 28 Jun 2009:
Bingo…spotted the AC/Delco unit on, of all places, Amazon.com!!
New unit $$99.95…wow!
Thx much Bryan…another ‘‘spot on’’ for you buddy! You should be
selling your knowledge Bryan…you’re amazing.
My Haynes book tells very little about rear shocks/springs
removal/assembly, but between it and all the great tips I’ve gotten
so far from all I think that’s a job I can definitely tackle. So
I’ll start accumulating all the parts. In Hawaii one can’t just
zip down to parts store or salvage yard in middle of a job…parts
are very constrained here. I have to online order almost
everything in advance so that does make for slow progress.–
Howard - '93 Vanden Plas 4.0L
Honolulu, HI, United States
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