I trust the guy who specked-out the Challenger O-Rings also could read a diagram about as well as you. One last try- no cut n past- no big words: Ever rebuild an conv. divided Master Cylinder? By memory, it goes a bit like this. Remove. Pop a C Clip. Remove any caps/ seals, then Cup. You then may find a piston/ spool. It goes back-n-forth and un covers little passages you may like 2 clean. Then ya get a little spring as the spool you will find next IS in line BUT not locked tougher Remove said spool #2, any cup, seal, inspect, hone, clean, flush, add new soft parts- reassemble. If you like to put down your handy-dandy down loads, you may find the Jag-T-III Master cyl aināt exactly built as that. Conv. (POWER or NOT) 2 spools to work based on 1 push-or release thereof. They push oil from 2 (effectively- normal cast in 1 assembly) reservoirs (Opps- lets say bowls) . Conv- all OK = spools kind o copy each other - apply more or less same energy to fluid from the same basic source. Still with me? Have a leak- 1 part cant easily jam other part, or completely drain all oil. T III set up has many similar parts. They say an ape has similar DNA as a person, but even drunk I wouldnāt like to take an ape on a date. T III 1 spool gets driver input, 1 kind of copies. 1 -1/2 (fronts gets boosted pressure as directed by drivers input, can get unbooted press only owing to drivers energy. T III rears only get boosted pressure directed by deflection of the primary/ front spool. T III queer up primary piston operation , rear piston gets real stupid- yet remains techectionally capable, Think the incredible Hulk - sleeping. Conv. Master Cyl (again power or no) queer up front OR back spool and other will try its little guts out to do as commanded by driver based on drivers input. Picture any 1/2 as the ālittle engine that couldā , if you must. Glad that is done. New business- At least can we agree that āI donāt know!ā is now on third. ???
Indicates stop WHAT ? 
Donāt mean t be off topic, but yeah, Alfa Romeo! 
If I were wealthy and had to drive something other than a Jag it would be an Alfa Romeo Montreal. So cool, esp. with those āeyelidā, drop-down vacuum-operated headlight covers. Iāve seen a video of one on the Autobahn leaving a Porsche 928S (which, IIRC, in its day had the highest h.p. engine of all production cars sold in the U.S. at the time) in the dust. 
Of course, those pop/push up āstargazerā headlights on the 928S were pretty damn cool, too. (can you tell Iām a sucker for moving headlights/headlight covers? 
). I donāt know why modern cars donāt have them anymore, but I have heard that is b/c they are supposedly a āsafety issueā for the feds here, and hence banned. 
Every car guy should own an Alfa at some point, I donāt think it even matters which one as they seem to do a remarkable job carrying that special something from decade to decade. Iād still be driving that 164 if I could have found parts for it, Iām spoiled and impatient I guess. That was right up there with my E30 as being a favorite to drive.
At a guess STOP driving as something is very wrong?
Rex.
There is a brake line that crosses at the firewall from the pump to the master cylinder. Be sure to disconnect the fittings and squirt Brake cleaner thru this pipe. Take the pump assembly off and flush every opening you can find. Same with the master cylinder. Did you say that you found a new master cylinder? Where. Mine is now leaking a drop or two on my shoe. I have tried to open it up as it probably only needs an O ring but no luck in unscrewing it.
Open the brake lines going into the calipers and flush completely. If you can figure out how to flush the calipers it would be good. I can not remember. There is probably a drain screw on the caliper. I suggest that you not flush the lines thru the caliper as it would just put more water and risk rusting the pistons.
I have done all of my work laying on my back in the yard. No garage. Be very careful as the car weighs as much as a minivan. I always use 6 jack stands on plywood so as not to sink into the ground. Also, I keep a jack under the front pad and the back. It only take a fraction of a second to fall. If the rubber bushing holding the axels peel then everything will fall and crush you instantly. I put the back jack under the deferential (sp) and also jack stands on the axels.
Do you have a convertible or a hard top?
Harry
Hey Harry, Iām lucky enough to have a two post lift in the shop to work on, youāre a trooper to do all that stuff on the ground. I havenāt seen a new nor rebuilt master cylinder/actuator for these systems myself, just a bunch of equally old overpriced used ones. Awhile ago I got a good deal on a pre-ABS pedal box and booster, luckily the booster is mint inside and the community has found an alternate master cylinder that is almost a drop in replacement so Iāll likely go that route when the time comes.
Mine is a 90 hardtop, Iām allergic to convertibles. 
Just like the Citroen ABS block failure that I postedā¦on the Teves IV system.
A whole industry has setup repairing ABS valve blocks, all makes suffer issues.
In the case you posted up, the fluid was leaking back internally and both the pressure and ABS warning lights were illuminatedā¦just as they should be.
The poster took the time to think what was happening and manually activated the ABS valves to free them off.
The valve only stuck due to neglect and he was jubilant that he had fixed it for no cost, meanwhile learning that the system is actually very simple.
You should take time to learn how the system functions.
STOP driving.
That is the main hydraulic pressure warning.
Citroens use a central hydraulic system for everything, steering, suspension and brakes. There is no backup manual master cylinder, as fitted to the Teves III system.
Incidentally, AFAIK, the Citroen XM was the last car in the World to be fitted with full power steering. Only on Lhd and V6 models upto '96. All other versions had regular PAS.
The Citroen brake system uses a pair of slide valves, very similar to the Operational Valve in the Teves III hydraulic unit.
One valve is fed from the main hydraulic/accumulator circuit at ~160Bar and feeds the front brakes, the other is fed from the rear suspension circuit and feeds the rear brakes.
The ABS valve block works exactly like the Teves III one, it is a recirculatory system, with active returns to the reservoir.
Citroen fitted this same basic brake system from 1955 until 2003.
Public acceptance, cost, and then being then owned by the PSA conglomerate, put paid to Citroen continuing to use power hydraulics in their cars.
Car manufacturers used to be inventive and believed engineering was important, now itās a race to the bottom and only cost/profits matters.
There will be no further innovative car systems and electric cars will drive the whole industry to the wall as cars simply become āwhite goodsāā¦disposable tech devices.
Car manufacturers intend to make more money from fuel supply (electricity), App subscriptions and data harvesting than from the cars themselves.
No one cares whether the car is innovative, or good/fun to drive.
Jaguar adopted the Girling brake system in the late 1970ās, which I believe has become the ATE Teves III after Lucas went bankrupt.
Girling were always a major manufacturer of aircraft systems and I believe this system is an adaptation of one of those systems, as it provides power function with mechanical reserve backup (front brakes only).
The front brake master piston is connected directly to the pedal and is not activated by the powered hydraulic pressure, only the drivers leg.
The power assistance is just thatā¦assistance.
The rear brakes of the Teves III are full power brakes only.
The two systems are not interconnected, other than when the ABS system calls for constant supply of fluid for the front brakes during ABS operation, at which point the Main valve is electrically operated by the ABS Ecu.
I donāt understand how the pedal will go to the floor, as the front master cylinder will still be functioning even in the complete failure of the pump pressurised rear system.
I suspect the brakes feel as if the pedal has gone to the floor as there is no gradual pressure pushing back at the pedal, the car isnāt slowing as effectively and when the pedal does actuate the front master cylinder, due to no assistance it feels solidā¦like the pedal has run out of travel.
It is actually due to the hydraulic fluid in the front brakes being incompressible, so feels solid.
This is the effect that AttyDallas has at present, due to no pump operation.
The front brakes are working, but there is no assistance.
Your comment about needing to clean the system out is the crux of the problem.
I once acquired a project Citroen which had been in a wet grass field for about 5 years having been taken off the road for a blown head gasket a couple of years previously.
The front brakes were slightly binding when released, so I went through the process of stripping the calipers to no avail.
Ultimately I ran flushing agent through the system for a couple of months and the brakes freed up and are still working as intended over 10 years later.
What is known as the āDoseur valveā, which works just like the āOperational Valveā in the Teves III, wasnāt fully returning to the Off position.
There was no more fluid being added to the front brakes, but the return to reservoir wasnāt open enough to fully release the pressure.
Cleaning the sludge out of the system fixed the issue.
I have known master cylinder systems suffer exactly the same problem, the difference there is that the brake fluid eventually overheats and causes vapour lock and no brakes.
It appears that posters here want to pay no regard to maintenance, or general safety inspections, have an inaccurate understanding of how the system functions, yet go on to blame the system for their failures.
Thanks for naming the culprit that spread disinformation about this system.
I have been avoiding naming them.
NASA were warned to not leave the filled fuel tanks outside in sub-zero conditions overnight, as it would cause the O rings to contract and leak the stored fuel.
So, what did they doā¦
My initial understanding of the internal construction of the Teves III hydraulic unit was mistaken as I had heeded the words of St.Kirby, that there is a special seal between the high pressure reservoir and the master piston, which could fail and allow pressurised fluid into the master cylinder. (Yes, I was duped too, for a while. There, Iāve admitted itā¦your turn.)
Upon re-examining the diagram I saw an active return between the boost and master pistons, which means no pressure in that area and also means no seal for St.Kirby and XJSBanger to look at re-manufacturing.
At least XJSBanger was right though when he said these system failures were down to Grandpaās running their cars with braking systems full of water and flat accumulators.
As a matter of interest when did you see this active return?
There may be a simple O ring/teflon seal on the actual pistons, but nothing to restrict free flow of fluid back to the reservoir.
The Teves III has a significant oversupply of fluid, so a slight leakage back to the reservoir is insignificant and is expected.
The system will still maintain full pressure pressing on the boost piston and feeding rear brake supply.
Do you have a definitive parts guide for the Teves III hydraulic unit? If you have, please share.
The original JagLovers thread where XjsBanger attempted to right Kirberts poor knowledge, yet insistence, but was suckered into believing there was a special seal inside the hydraulic unit.
Teves ABS - Project Refurb - XJ-S - Jag-lovers Forums
That āspecial sealā is just a piston guide called the Positioning sleeve. The sleeve and spring smooth out ABS feedback into the pedal.
Image from that threadā¦
As far as whether I have ever rebuilt basic master cylindersā¦I grew up driving and working on on rubbish quality British manufactured carsā¦one quickly learns to buy a foreign made car.
Apparently there is a rebuild kit for the Girling system, which may well be the same unit.
Have you contacted either Jaguar, or Teves to see if there is a rebuild kit.
If these systems are so poor and people are āthrowing them over the hedgeā, why are they expensive second-handā¦surely they would be giving them away.
I think you have been suckered into the Kirby doctrine to replace your Teves III with a pre-ABS system and have already bought the stuff to do it, so donāt want to believe the Teves III is reliable.
The Alfa 164 was a four model platform.
Saab 9000, Lancia Thema, Fiat Croma.
Alfa, Saab and Lancia were semi-interestingā¦the Croma was dull as dishwater.
As you probably know, Fiat already owned Lancia and Alfa.
The Alfa came later than the others and was a bit reworked in the suspension and actual metalwork, such as door frames being different.
The other three were reskins of the same car, real badge engineering.
More bad news folks.
As well as the Teves III system being used by Jaguar, Cadillac and others, apparently it was also used by Ferarri and Volvo, who as we know are serious risk takersā¦
Most amusing, āDieselmanā Iāll be polite, lest we call you āwind Mill Manā. See if I got some of this. Mr. Kirby is wrong. Convenient he sold his PRE Tev III car, right.?? We all do not understand and properly maintain the cars that we own. You mastered an obsolete break system solely by printouts and hearsay. British cars are rubbish. You do not own any Jag. You like to tell all that do that they are wrong. You like to āre energizeā resolved threads. You never maintained a Teves III, or any Jag break system. You are confident enough to tell those that own cars that you do not (will not??) drive what is safe and what is not. You and only you are smart enough to understand how to define stuff like āpower breaksā , āconnectedā et cetera. You are astute at knowing that a Pump installed due to an ABS System should NEVER be referred to as an āABS Pumpā . And you can predict component failure rates, to the fraction of a percent, by tea leaves or such. Lastly, you know that unknown/ un- specified āengineersā are somehow so bored that their priority (especially in retirement) is to āget Youā. Lastly, you are fun at parties. Do not French car guys maintain a computer forum thing will benefit from your general glow?
Every relay manufacturer gives a specified number of actuations for the life of that relay. They are considered a service item.
Apologies, had to raise another post, canāt edit the other one.
[quote=āJp2, post:157, topic:440865, full:trueā]
Do not French car guys maintain a computer forum thing will benefit from your general glow?[/quote]
Of course. People used to consider the cars in question complex, poor quality, impossible to maintain as a DIYāer and rubbish.
As a result of posters like me answering calls for help and queries, providing all the technical information we can, allied to knowledge based on practical experience, the cars are now regarded as worthy classics that anyone can maintain themselves on their drive.
We now have a growing number of worldwide owners including new USA owners where the car was never officially imported, who now are confident in performing their own maintenance.
If we have a system we donāt understand we endeavour to investigate until we have definitive knowledge of how it functions.
As a result, calls for help on the XM forum have reducedā¦and more of the cars are being used as daily use carsā¦which is a good thing.
I came across this thread with a call for assistance from AttyDallas and having a reasonable level of knowledge and experience of power braking systems, was sure I could provide some further information, so did soā¦at which point you responded negatively.
Perhaps if this forum focussed on having a library of information with āhow toā repair threads and a desire to assist members with their issues, you would have quieter, but more constructive forum.
I would have expected there to be a dedicated thread with all the technical information, manuals, wiring diagrams, etc, readily available for members to download and follow.
Any unsure poster could then ask for specific assistance, such as electrical fault finding.
For now, letās just focus on getting AttyDallas over the line.
Mine has gone almost 250k, itās been plenty reliable all things considered. Largely due to it spending very little of its life sitting Iām sure. Itās been comparatively trouble free in general vs a lot of them for the same reason. But everything wears out eventually. If I have to pull all that jazz out and clean things like it should be, something simpler is going back in itās place. Plus Iād like to mount an ecu where the pump is. I donāt have argument with kerby maybe being wrong, you maybe being right and you both knowing the thing better than I do. Itās still over complicated and antiquated and parts availability is only going to get worse. Iām not going out of my way to rip it out while itās working but whenever I do a serious engine out service, itās gone. Iāll take a master cylinder and a vacuum booster over pumps relays switches ecuās and that actuator unit any day. Especially when I can still have abs with pretty minimal effort. I appreciate your sharing your info on these things here and hope you keep it up, but all the reasons I donāt want to deal with it remain.
This same sort of discussion happens about the v12 btw. People lament it and replace it with something else, then folks come say nah you just donāt understand it, you have to do this and this and this is how it works, and then the response is generally yeah I see that and donāt see a compelling reason to. V12 is a fine and fascinating motor, the teves brakes are quite interesting. No compelling reason to have either in my life given the alternatives within my reach though.