Total Brake Failure

[a19kjr]

1989 XJS V12 Convertible.
Had the car about 13 years and kept maintained regularly, with only 33k miles to date.
Parked in garage last 6/7 weeks.
All working well when last driven.
Tried to start and dead battery, so replaced with new battery (well overdue) and all good.
However, tried to move the car and NO brakes, pedal goes right to floor with minor resistance initially then none.
No work done on brakes for about 3 years when caliper replaced, brakes all good since then.
Checked all around, no leaks anywhere and reservoir full to max.
With key out pumped brake pedal 10-20 times, no resistance and no build up of resistance on pedal.
After that found brake fluid weeping out of air hole in reservoir cap so fluid build up in reservoir after pumping pedal.
Initial thoughts go to master cylinder seals but is there any other explanation?

Grateful for any advice since I have not taken a serious look at the braking system before now.

[ptjs1]

a19kjr,

I've never heard of the seals failing on the actuation unit of a teves-equipped XJS, so I wouldn't start there.

If you've got no leaks in the system, I would start by bleeding the brakes.

Although I don't think your issue would be in the low-pressure side, it always makes sense to bleed this first before you bleed the wheel circuits.

So, start with the LP side first then do the wheel circuits. And my suggestion is to do the rear brakes as per the Teves procedure, rather than as per the Jaguar procedure.

Good luck

Paul

[poprivet]

I would think that with no pedal resistance there must be either a hydraulic leak, but you say the reservoir is full, or a lot of air in the system. Does the accumulator motor run and are there any warning lights when ignition is on?

Obviously a serious problem and one that is difficult to diagnose without seeing the car. You say it has been correctly maintained, when was the brake fluid and accumulator ball last changed? Maybe there is someone on here near you that can have a look and advise.

Al

[PaulGover]

It may be me, but I found bleeding the brakes on my '91 XJS, with I think a similar Teves system, very difficult. It took a lot of goes to bleed the rear brakes in particular.

[a19kjr]

Thanks for your various advices so far.
Just getting back to take another look today and have gathered as much info as I can find in the meantime.
Picking up on a couple of points raised.
Brake fluid last replaced when new calipers fitted about 3 years ago. No problems since.
No knowledge that accumulator has ever been replaced, certainly not in my ownership. (13 years).
All lights go out after startup.

Brakes were good 6/7 weeks ago when car last driven. Have never seen air in a system have a sudden effect like this, usually a progressive effect results from that. So, not discounting that, but will start working through and report what I find.

[a19kjr]

Report on today's first step investigation.
Objective at this stage to establish the integrity of the system.
1) Pump runs and trips out as expected.
2) Warning lights go out
Conclusion: Boost pressure being successfully achieved.

3) First push on pedal gives small resistance, additional pumps with resistance almost non-existent. Feels like a pressure release taking place.
4) Studied the electric and hydraulic circuit diagrams carefully and it looks to me like a stuck outlet valve on the valve block would produce the hydraulic pressure release exhibited by the pedal behaviour. No easy way to test for this that I can find.
5) Jumped the diagnostic plug on the brake ECU and checked for DTCs. Nothing stored, so no electrical system diagnosis to help here.
Conclusion: may be worth trying ABS diagnosis with multi-meter to see if any valves have readings out of whack. Looks a fiddly job to get at the ECU pins for this!

So, a bit learned, some knowledge of the system gained but no actual progress on fixing the fault.
I appreciate that bleeding this system is a non-trivial exercise and reluctant to jump right in to that without establishing that the system otherwise has integrity. Would be really annoying to go through that process just to find it does nothing because for example, a valve is stuck and a full strip down is needed anyhow.
Will study things a bit more before the next step.

With your better experience of this Teves system some of the above may open a door.

Thanks again for your help.

[ptjs1]

a19kjr,

Try checking the integrity of the ABS valves by applying current to each of them. You should hear a clicking sound. I'm away and don't have access to my technical material at the moment, but from memory, on the plug, there's a common earth pin and then each valve utilises one input voltage pin. I'll look up more when I'm back home if you don't have access to the technical material.

Good luck

Paul

[PaulGover]

With luck you should get your brakes working. If not, for info, I had problems with my Teves system some years back and got a decent replacement master cylinder/control thingy from a breakers yard. I later discovered that Teves do (or did, at least) make repair kits, though you probably need a clean room to undertake overhauling these systems. Jaguar don't list them, as far as I know; I don't remember where I found it.

[a19kjr]

OK, next step.

Checked circuits again and set up a table for testing the valve block.
Noted doing that issue 2 of the ABS diagnosis procedure from Jaguar has a fundamental error.
It consistently states pin 7 as common when it should be pin 1. The other pins references are OK.
However, used the data from that to confirm status.
Table here for reference. May assist others to have the layout as shown.
Sorry the table gets a bit mangled when posting, but follows in sequence.
Have put comma separators in to help a bit.

Jaguar XJS - Teves ABS System - Valve Block Integrity test Test Date:2/3/2019
Pin 1 on connector nearest bulkhead

ECM Pin, Description, Pin, Cable, Colour, Coil, Valve
,,,,, Resistance, Action
11, Common Ground, 1, WR, White / Red,
35, Inlet – Front Left, 2, GW, Green / White, 5-7 Ohms, OK
16, Outlet- Front Left, 3, WK, White / Pink, 3-5 Ohms, OK
33, Outlet – Rear, 4, GR, Green / Red, 3-5 Ohms, OK
17, Inlet - Rear, 5, UG, Blue / Green, 5-7 Ohms, OK
34, Outlet – Front Right, 6, LGY, Light Green / Yellow, 3-5 Ohms, XX
15, Inlet – Front Right, ,7 WN, White / Brown, 5-7 Ohms, OK

We usually hate to be proved wrong but in this case I am really disappointed to be proved right, there is a stuck outlet valve!!
All coils OK, tested the resistance of them first and all in range as shown above.
Triggering each coil gets a clear click on actuation except for pin 6, the Right Front Outlet.
The coil is OK and draws current when trying to fire it but no movement.
Conclusion: RHF Outlet valve stuck open with some crud......so the dreaded strip down looms!

No need to rush at this, so will probably leave the major work a few weeks till the weather improves.
(hate working in really cold garage) In the meantime, get all prepared and consider things like changing bleed valves to no-return type just to make thing easier for the longer term.

Any further advice very welcome.

[a19kjr]

Image of table may be clearer, attached here.

[steve_m]

Not sure if it is of any use but I have a brand new JLM 11336, ABS valve block that I am selling.
I don't know if it will fit yours though?

[PaulGover]

...
Conclusion: RHF Outlet valve stuck open with some crud......so the dreaded strip down looms!

No need to rush at this, so will probably leave the major work a few weeks till the weather improves.
(hate working in really cold garage) In the meantime, get all prepared and consider things like changing bleed valves to no-return type just to make thing easier for the longer term.

Any further advice very welcome.

As I had a broken control block to play with, I took it apart. It's nothing like a normal master cylinder; the valves are small things made of plastic wafers that look very fragile. Also, as far as I recall, there's an operating pin with some adjustment tolerance measures in tenths of a thou. IMHO it needs a clean room to work on it. If you feel brave, good luck, but I recommend having a backup plan!