91 XJS brake failure

XJ-S
1

So the wife and I were having a lovely end of season run, up one side of the mountain, down the other, lots of fun 15 mph switchbacks, 150 miles or so, and a mile from the house the brake pedal sinks to the floor, and nothing happens but the right rear locks up. By divine intervention, I was travelling slowly, and there was no traffic, and the light turned green just as I arrived at the intersection.

It is, of course, the Teves. Put an accumulator on it a year or two ago, it pumps up in under 45 seconds, (it’s the next size larger than what came originally) and currently takes 4 or 5 squishy pumps for it to turn back on. I bled the system per the book after awakening the car from a 10 year slumber back in 2020.

Symptoms: almost exactly at the halfway point in the trip the right rear brakes squealed coming to a stop. Has never done that before, and didn’t do it at all on the way home.
ABS light is on, has been, don’t know that it has ever worked
Felt something not quite right at the stop light about 2 miles before the one where the pedal went soft.
upon putting it into it’s resting place, the brakes sort of worked, although with a very soft pedal.
now if you press the brake pedal, it sure feels like there is air in the front circuit, with the pedal seemingly finding something solid near the bottom of the travel.
Any other car I would be blaming the master cylinder, because the brakes were working and then the pedal went squishy with no other issues.
But this is the first car I have had with this system, and all I’ve read says the master rarely decides to quit.

So what’s is all yall’s opinions on what could be happening here?
Was the squeal was the pistons in the caliper coming loose, and travelling far enough that it took more than one pedal travel to make up? But that wouldn’t leave me with a squishy pedal now.
The accumulator ruptured? But it’s still pumping up.
Give up on the ABS and put the previous generation master cylinder on it with the booster, and abandon the Teves?
I need something to hang my hat on, my wife already doesn’t trust the car, and frankly, if all I do is bleed it and all is working again, I’m not sure I can either.
I have been running this car all summer with no issues, and the fluid is less than two years old.
My OCD kind of demands I know what went wrong before changing anything.

Thanks
71MKIV AKA Steve
71 Spitfire
91 Jag XJS classic convertible
“reliability is overrated”

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Hi Steve I had same exact thing happen on mine last year. As it turned out both front calipers seized. And since I pressed on brake relentlessly to stop car, my right rear brake locked up…

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Can’t offer you any advice on the issue, unfortunately; I am curious about upsizing the accumulator - was it a GM part / can you share a part number?
Thanks!

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Yes yes, Teves, Teves is the one to blame, what a rubbish system better to remove it… Aston Martin was using it, Ferrari was using it… Somehow only Jaguar “lovers” are having problem with it. Not that it’s the neglected condition of the XJS platform - owned by SaladFinger-owners for the last century just because it was in the British TV series. You don’t need to wash your hands after using a toilet, you don’t need clean nails, you don’t need a teeth, just XJS on your driveway. It’s almost like with iPhone owners these days…

Anyway returning to ABS issue - can you clarify what you meant by ABS ligh being on? Was it on before or all the time? How much fluid you’ve drained while bleeding the brakes in the past? Have ypu tested brake accumulator pump already? Ho to check and replace Brake Accumulator in your Jaguar XJS

The size of sphere may vary and won’t change anything unless you’ll double it…

Have you changed the flex brake hoses.or inspected them?

5

still right at 100 bucks.

For a early 90’s Cadillac I believe.

Since I found this, I have discovered that a fair number of agricultural equipment manufacturers use these accumulators, and a visit to your local friendly hydraulic supply house that caters to the farmers would likely be able to get you one as well.

S

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So some additional information,
no codes in the ABS computer, last time I checked, might be worth doing it again. I have gone through the whole ABS troubleshooting procedure from the shop manual as well as replacing the computer. It seems like… :man_shrugging: …maybe the front sensors are covered with grease oozing from the overly enthusiastically repacked bearings, in which some metallic dust has collected, shorting the sensor to the point that they aren’t sending any signals to the computer.
The front calipers were rebuilt with new stainless pistons and new seals during the recommissioning so I don’t think they were dragging enough to boil the fluid? But this happened after a trip of over 150 miles, so even not dragging it was probably pretty warm.
If the brake fluid has boiled, wouldn’t it condense once cooled and start working again?

Hmmm, bit of an epiphany, two years ago I put ordinary brake fluid in there, this is a standard British system where it’s open, right? there’s no little flexible seal under the cap, so the fact that I don’t have the system filled with the LMA fluid…
My Spitfire boiled it’s fluid once, that was exciting.

I have not dropped the rear subframe out yet, so the rear calipers have not been gone over, when that happens, my ocd will demand the stainless pistons and new seals, and they will work much more better with new paint.
All the flex lines in the car have been inspected, and do not show cracking or wear or any aneurisms.

I think that answers the questions, If anyone has any other ideas chime in.

S

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Thanks for responding re the accumulatorđź‘Ť It turns out that I used that same part a couple of years ago, without realising it was over-size!
Good luck with tracking down the problem.

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it’s just the next size up, the original was 1/4 liter, while these are 1/3 liter.

S

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Steve,

You have more than one issue here.

First and as mentioned above - your rear caliper is probably seized. Replacing it will give someone a bit of tears, you don’t need to drop rear frame to do so. Stainless pistons are good - “replace&forget” option but technically and with average age of XJS owner - any replacement piston will last forever* (* remaining lifespan of XJS owner).

ABS light will stay on if the brakes are not bled entirely (hence question about amount of fluid drained during historical bleeding). Have you used vacuum bleeder?

Forget about standard troubleshooting of ABS system, it all depends on your location and humidity. Have you changed front brake rotors in the past? If not have a look at the photo below:

tmp-cam-2785106712082653713
tmp-cam-27851067120826537131224Ă—1632 212 KB

These rings are rotting out / changing into rusty hedgehog - causing issues with signal. Grease is a street legend, discard it.

Soft pedal at the beginning of depress shows problem with rear circuit, not the front one. The hard “step” at some point of depression is actually engagement of the front circuit which can work without pressure in accumulator’s sphere (…but harder).

Your ABS fluid tank has a sections - you have to fill it up to the neck to perform any successful bleeding. If you haven’t done that - it could be low level of fluid in accumulator section from ancient bleeding.

Well hated “Teves” ABS s actually ATE - well respected German manufacturer. How you’re designing and running British pipes along XJS is another thing…

Have you tested your sccumulator as per link given earlier? Accululator assembly has more than just a sphere to fail - f.eg pressure switch will give you similar symptoms.

As far as I can recall - most of the Teves issues results from insufficient / incorrect bleeding and can be rectified.

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fwiw LMA was just good DOT4 for all intents and purposes, I’m not even sure you can buy it anymore.
With the exception of DOT5 silicone, brake fluid is brake fluid other than its boiling point and how readily it gathers/holds moisture far as anyone has ever been able to prove to me.

When mine goes, it’s outta here. Vacuum booster and a master cylinder will suffice.

Fun side note.
I met a guy at a car show last summer with a shelby cobra replica, with a jag IRS rear, and a 5L v8 and such out of an early 90’s mustang. What caught my eye, was he’d used the ABS unit from it as well.
I questioned him about it and it was, back then, a pretty closed, simple system that was just as happy to work on the Cobra as it was on the Mustang it came out of. He’d built it a lot of years ago and had a ton of street miles and track use, said it worked just like you’d expect in any other 90’s car.
If I WAS going to have ABS, which I don’t have anything against if it’s reliable and reasonably serviceable, I’d rob one from a car of that era.

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Thanks everyone.
Regards to the bleeding, I did not use a vacuum bleeder, and I didn’t pay too much attention to the amount of fluid that was pushed through.
So let me get back out to the barn, it’s harder now that it is cold and dark, and do some things, and I will report back.

S

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So an update, it turns out that the valve block seals decided to leak, and dump the fluid overboard. From the crud in the electrical side of the block, it’s been doing that for awhile.

Bought a “used, serviceable” unit as we used to say as airplane mechanics, and installed that, and now cannot for the life of me get the rear circuit to bleed. Many quarts later, the rear circuit is still just as squishy as it was at first. Key on, pump stops, pedal pressed, rear bleeder opened, 15 seconds, bleeder closed, key on till pump stops, key off, allow pump to cool.

I have a lead on a booster/master cylinder/reservoir/pedal box from an earlier car, so I think I am just going to go that route.

I sorta have to do something like that, or my wife will refuse to ride with me in this car, as this brake problem, and watching me try to fix it, finds all of this quite disconcerting, and will feel better with some major components being changed.

other suggestions?

S

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After reading Kirby’s book about this brake system, i believe ALL XJSs will need to go back to a vacuum booster system one day.

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Except for the 1995.25 and up XJS’. Completely different, simple, and modern ABS.

Jon

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So is it 89-95 with the bad abs system? My 88 has booster.

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Not necessarily bad, but more complicated and more difficult to service than other contemporary ABS’.

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and what I am finding is that new seals and o rings are made of unobtainium.

S