After my recent Brake Problem:

https://www.jaguarforums.com/forum/x...60-mph-145427/

Does anyone know if its possible to disable the ABS on the 'Teves' ABS System, so it brakes like a normal Brake Booster System.

If so this could solve the problem and could be a very easy fix for myself and anyone else.

This is the Second time this has happened to me on Two different XJS's and while I know how to fix it, I just don't trust that ABS system at all.

 

I simply do not know about the Teves system.

My X300 had intermittant activation of the ABS at "carpark" speeds, and the fault is/was well documented.

I simply unplugged the large power plug at the "eletrickery bit" under the ABS unit, and that activated the dash light, BUT, it stopped the stupid action of the ABS.

Being the D Driver at the time, and time was against me, a repaired module was duly ordered, and the car driven in the unplugged mode for some weeks.

NOTHING happened, NO Lucas smoke excaped, the brakes stopped the car, OK, no ABS, so what, in MY opinion. The XJ-S never had them and I never had issues with that beast.

The Orange light drove me nuts, so I reached up and removed the bulb holder, problem solved.

New module fixed the car, but, honestly I never noticed any difference in brake performance. Bear in mind we get NO snow, NO ice, etc where I live. Dust, dirt roads, etc are the norm.

 

OB,

I share your concerns, particularly after your recent incident. The Teves system is a complex comprehensive system. If you read through the manual and understand exactly how it works, you'll realise that it's not just an ABS valve block. It's far more comprehensive than that using an actuator unit, an accumulator and pump, power activation of the rear brakes and electronic activation of the ABS solenoids.

I guess it might be possible to force the solenoid valves to remain in the open position. However, I am sure that any insurance company will be all over you like a rash if you're unfortunately then involved in an accident.

If it is your ABS valve block that is gummed up again, I think you've just been unlucky or that POs have not given the system the regular flushing and maintenance that it needs. Most of us have had no problems with the system apart from regular maintenance.

Realistically, I think you only have 3 options:

- Repair the system to fully-functioning capability
- Upgrade all the components to the later 1995.25MY ABS brake system (expensive option and a reasonable amount of work)
- Downgrade to the earlier non-ABS system, re-MoT your car and then advise your insurance company and pay the inevitable inflated premium.

My choice? I'd fix it. The amount of knowledge that's out there, including your own recent work on doing the other ABS block, would give me the degree of confidence that you can get the system working in peak condition again and continue to enjoy what is still a great car.

And remember, as with any question posed to the Forum, you're not going to get a common answer!

Good luck with whatever choice you make.

Paul

 

Hi Grant

I am dying to try that, not literally I hope! but there is more than one plug on the ABS, so which one do I pull?

Although I know how to fix it, its still a real PIA Job what with Bleeding the Brakes and everything else.

I'm no fan at all of the ABS, I just can't tell the difference when I drive my non ABS Merc.

Except of course that isn't as much fun!

I'd rather have non ABS that I know is going to Work, than ABS which keeps on trying to take me out of the Game.

Later on I will possibly take up Paul's suggestion and fit the later unit or maybe NOT! if unplugging it solves the problem.

My Insurance Company are OK with Mods, as long as you let them know what you are doing.

So which Plug do I pull Grant?

No comebacks if it all goes wrong, I'm up for being Test Pilot and will give it plenty of Car Park first to see how She performs.

I had a feeling the WoOZ might have the answer!

 

Hi Paul

Its also a great big PIA and so I am already loving Grants idea!

But after the Summer, assuming that the ABS hasn't killed me by then, I would certainly Consider using one from a much later Car.

I might also Contact TWR and see if they do any mods.

So Thanks for your Suggestion, which is appreciated.

 

Alan, Paul is 100% right.

Question for Grant: Did you have to exert more pedal pressure Grant?

Greg

 

There is only one way to find out Greg, I just need to know which one of those plugs to pull out.

And I will take her for a Canter round the Garden before moving on to the Car Park and beyond!

 

The X300 has a vac booster, so a different system entirely.

NO extra pedal pressure. In fact I felt the brakes worked better with the thing disabled, and I also reckon that I had more pedal feel also.

The car here that was converted, a 1988 Conv with the same issues as Alan has, was done in 3 days, and all he had was the booster and master cylinder from a weecking yard. Alan has a COMPLETE donor car, so simple by any standards.

I was not involved in any way. I know the guy and he is competent, but getting info from him is worse than getting a straight answer from a pollie.

I have looked at the parts drawings prior to typing this, and I reckon the metal pipes and T connector in the engine bay will be needed. The vac take off at the rear of the RH inlet manifold is possibly already on yours with a simple "cap" on it. If not, take it from the inlet of the other car.

The non ABS master cylinder will be mandatory.

Apart from some sliced knuckles etc it should not be that hard.

As for which plug, no difference, any plug should disable the system, well thats my logic anyway.

Having said that the lack of "pump" and its system could mean a rock hard pedal and NO retardation at all.

 

in the event of the system detecting a fault, it reverts to a conventional braking system

this means the ABS feature ( and it is a feature ) is disabled ,

ABS only works when a wheel sensor detects lack of rotation during braking, other than that it plays no part in braking during normal situations, the pressure sphere is to compensate for the lack of a vacuum brake booster , and provided a reservoir of pressure should the pump fail...

the system can be disabled electrically by pulling the main ABS fuse, but leave the ABS pump fuse in so the system works boosted , but this will throw the fault light in the instrument cluster

you should then think about getting the system repaired as soon as possible , as advised above, I doubt the insurance company would look favourably in the event of an incident resulting in a claim ??

the choice is yours

BB

 

Hi Grant

Check your email for the Full Story!

But I am very lucky in having a Private and deserted road backing onto me.

So this is what happened, when I disconnected the Big Plug from the Teves ABS.

Sensible Precautions Observed for a Test Drive first in the Garden.

Hand Brake on, Gearbox in Park etc, Ready to cut the Engine.

Now with the Engine Running and Gearbox Still in Park, I had a Rock Solid Pedal! of the like I've never had with the ABS working (Is that OK?)

All the Lights went out except for the Orange ABS one.

Let her run down the Garden at minimum Speed then hit the Brakes and She Stopped nice and straight.

Repeated that over and over, going faster each time.

Same result She Stopped Perfectly Straight every time!

Opened the Gate to the Private Road (which is deserted) and gave her a much Faster Test Drive.

Then hit the Brakes so hard that it left Skid Marks!

Same result Perfect Braking every time and no extra pressure needed on the Brake Pedal.

Which as I've said was the hardest that its ever been, with almost Zero take up in the Pedal.

Again just wondering if that is expected and OK?

With the ABS on, under hard braking you get a Sort of Ratchet Ticking noise.

Which I am presuming is the ABS trying to decide which Wheel to Brake, or in my Case, Not to Brake at All!

With the ABS Plug off, I'm still getting that Ratchet noise but She's pulling up Straight. Is that OK and expected?

Its going to take a lot of short drives to build my Confidence up but the sooner the ABS is replaced with the Brake Booster System the better I will feel.

 

Hi BB

Of course you are right but early indications seem to indicate, that She Brakes much Safer without the ABS.

As you know I've pulled the Plug but where is the fuse?

Thanks for your help.

 

OB,

Without wishing to sound dramatic, I would sit back tonight, read the manual and get your head around the situation.

This system is complex and does not operate like a conventional braking system. The fluid to the rear brakes is not driven by pedal pressure but is a dynamic circuit with the fluid being sent directly by the pressurised booster which is assisted by the pressure in the channel from the accumulator which is built up by the pump.

If you have a hard pedal then that SEEMS symptomatic of the accumulator pressure having dropped below 140bar and the pump not being able to increase the pressure back up. That seems to imply that you would have no rear brakes and an unboosted setup of the front brakes. Are you sure you haven't disconnected the pump electrics? I'm not sure if just disconnecting the Brake ECM can give you a harder pedal? Mind you, if the accumulator pressure dropped that low, I would expect it to illuminate the brake warning (not ABS) lamp, so maybe I'm wrong?

I know it sounds an awful pain but I'd be going back to the root cause. I appreciate that your failure may have "gone away" for now but you may be able to find a fault code using the "blink test" procedures described in detail in the manual. If you then run through the ECM erase procedure and repeat the blink test you can see any residual faults. After that, I would run through the 32 defined diagnostic tests with a multimeter which will test all the potential electric faults including the inlet and outlet solenoid valves. It'll be 30 mins well spent.

Your description of a pull to the right when touching the brake (and not inducing lock-up) seems to imply that the input solenoid valve on the left front wheel has closed (and stayed closed) whilst the outlet valve has remained open. This has caused a pressure drop on the left front wheel circuit and a violent pull to the right as the other 3 wheels brake.

OB, I sense you're reluctant to go through this section of the manual. But it is hugely informative with its description and diagnostic routines. And you are going to have to read it if you're think of upgrading (or downgrading) the configuration anyway!

Go on, fix the problem! You've got the competence and the experience to do it! And we're all dying to see some more pics!

Good luck

Paul

 

Hi Paul

It is beginning to sound like one of the Solenoid Valves in the ABS Valve Block, exactly the same as what happened on my other Car.

Is that the Valve that you are talking about?

If so it's an easy fix but a PIA to do, to stop Brake Fluid going everywhere.

If so this time I'll re-wire it but the Teves System on these old Cars, is just so unpredictable, that you never know when disaster is going to strike.

There is no progressive Warning, if one of those Solenoid Valves packs up, then the result is instant.

Greg kindly sent me a diagram of the Brake Booster System, which doesn't have those kind of problems, so I may well put that on instead from one of my other Cars.

But I'll hang on to see what Grant may have to say

The Brakes were really awesome, with that plug removed and when I hit the Anchors, all the Brakes locked up which is the way I prefer it, as that's how it used to be back in the day.

But could easily Control it and much prefer to have Brakes like that, to the unpredictable ABS.

Over which you have little or no Control at all, if/when it goes wrong.

 

OB,

I had this issue in my old Land Rover Disco at about 315k miles, except, on top of the pull it also so nicely blocked the primary channels to the front brakes and pedal pressure went from normal to pushing against a wall with maybe 15% braking ability! I about filled my pants / went right through a four way stop (deserted, thank God).

Am a huge fan of kicking 90's gen ABS garbage to the curb. The TWR's cars likely had dual masters with infinitely adjustable bias blocks. I use the same setup on my track cars (and one quasi daily driver) and its the best modulation / pedal feel there is. No assist is needed. I too like the stock brakes on my '85 although, they work just fine sans the fancy junk / is what I would do in your situation.

Best of luck.

Jeff

 

Hi Jeff Yeah!

I know only too well how you feel and this would be the Second Time, that my brakes have failed on two different XJS's.

No warning! one minute the Brakes work fine and then next second they don't!

So I'm used to it now (Lol)

Unfortunately Spares are unavailable, at least with the Main Suppliers, all posting NLA.

So having run an electrical test with the Unit Still in the Car, I know whats wrong.

Its either a Faulty Valve or a Broken Ribbon Wire inside the Valve Block.

Which are so darn fragile, that you could break one just by looking at it.

So without removing all the Stuff that I did last time, I will just get a Valve Block off an XJ6 and after Changing the face plate, bang it on and bleed the Brakes.

AL

 

Hi Paul

I've put on another Valve Block, that I took off an XJ6 after Testing it first!

All back to normal, all working OK although I still don't trust it, not to give a problem in the future.

So I'm planning to rebuild the one that I just took off, then put it back on.

 

OB,

Good work, well done!

I know brake failures are scary. I well remember when the fluid boiled on a "talking" Austin Maestro that I had! Swerving wildly, slamming it into 2nd gear and juidicious use of the handbrake finally brought me to a safe halt! Neither I nor the computer in the car were able to talk for a while after that!

However, now that you understand how the solenoid valves work, it should give you a (slight) degree of comfort. The symptoms you experience only arise in those bizarre situations where the inlet and outlet valves get confused in the middle of those extremely fast ABS cycles, or where the inlet valve has not immediately opened after closing. The description in the manual will help you to understand how unlucky you were for that precise failure sequence to happen.

With your very careful cleaning of the valves and any necessary re-wiring done, I would suggest that the chances of that type of failure happening are much less than typical fluid boiling or master cylinder seal failure to which any non-ABS system could also be prone.

When you fix the original block and re-install it, run through the defined 32 diagnostic checks on the ABS ECM. This will give you the assurity that the electric circuits are all giving positive continuity readings, particularly the solenoid valves. And your cleaned, repaired block will be better than any 25-year old 2nd-hand unit.

Drive safely

Paul

 

Brakes:


I went through several cars before I was abut twenty, before I finely got one with reliable brakes. Cable or rod operated, Hard pedal. pull to one side or just not stop.
gear down, assist with hand brake and keep an eye open for an escape route.
At last the little 41 Studebaker Champion hydraulic brakes. Poopless, though.


As I understand ABS, it prevents lockup and thusly skids that are not effective in bringing a car to a stop. Pressure just short of lockup being optimum.


My Jeep has ABS. So far, so good. "knock on wood". Brake pedal very topuchy compared to my Jaguar.


My 83 XJ wuzza six. has no ABS. And, I've had to brake hard a few times. No lockup and undesirable skidding. Jut squats and stops, much like a good cow pony!!! I like it that way.


In the early 60's my freeway flyer commuter truck, a 57 Ford short bed blew a brake line. No brakes at all. I nursed t home on surface streets. The 4 speed "granny" helped retard any velocity. Recalled old skills as to "escape routes"


In the USA, insurors don't have that amount of clout. Hit a car, illegal mod, too bad. Nope, perform as written. If the insurer wishes, they can cancel.


However, if the opposing party gets wind of the messing with the brakes, big bucks. Possibly even punitive damages. Wanton disregard for the welfare of others. Not mere negligence, gross negligence.


Aired up the Jaguar tires. The hard way, as is my custom. My big compressor blew a regulator. Massive air leak. Wrestled the not so small one around and got to all four. It is on wheels now!!! Good old HF convertible hand cart!! Now in four wheel mode. Two fixed and two casters.


Carl

 

That's why I replaced it, so hopefully no more problems in the future.

 

Hi Paul

Valve Block now replaced, so hopefully no more problems.