Our 1994 4.0 XJS Convertible pulls hard to the left, usually after immobile for an hour or more. Then when driving again and applying brakes, it pulls hard to the left. We have replaced both calipers with no improvement.

The dealer is of no help any longer due to car's age but did suggest the ABS valve block may be at fault, they also said it is no longer available.

Do any of the forum have a similar experience, know of a repair/rebuild shop with reasonable costs or know where I could obtain rebuild specifications and instructions?

All suggestions are appreciated.
Thanks, Gerry

 

Does your ABS or Brake warning lights come on when you start the car, and go out after the self-test at start-up?

 

Mac,
Yes, all dash lights, ABS and brake, illuminate upon turning ignition switch to on and then immediately extinguish when engine is started.
Thanks
Gerry

 

Unless the 1994 has a different system than the Teves ABS system first used in the XJS, the lights shouldn't go out immediately. The system runs a self-test and the light shouldn't go out until the system is pressurized.

Try pressing the brake pedal a dozen times with the ignition off, then start the car and see if the ABS light stays on until the pump reaches pressure.

If you have a failing valve in the valve block, it should flag an error and turn on the ABS light.

 

Hi Gerry

Does your XJS have a Teves ABS Master Cylinder Actuator like this one?



The Teves ABS Master Cylinder Actuator.
If the Valve Block goes wrong, the Car can pull to one side under sharp braking.

If so the Valve Block on the Side which is NLA could be the cause of the Problem.

The very same thing has happened to me, where the Car suddenly pulls to the Right on a (UK) Car and tries to ****** the Wheel out of your hand.

Although results are NOT Guaranteed fixing it is easy (Relatively Speaking!)

And will only cost a Few dollars, about $25!

So don't let any dealer give you BS that this will Cost $1,000 cause it won't!

I've only done this on my V12 XJS so it all depends if your Master Cylinder Actuator, is the Same as in the Photo.

If not can you put up a good Photo of the Valve Block as it might be the Same.

 

Thanks...will be eager for details to repair what may be an issue with the ABS valve block..really like your cost.

I'll try to attach a couple pictures. Maybe this will help determine manufacturer and if like that on your V-12. Fingers crossed for that repair!!!
Gerry

 

OK, just performed the second part of your test. Pumped brakes 12 times with ignition off. Started engine, ABS (yellow) and Brake(red) lights stayed lighted for approximately 3-4 seconds and then extinguished. Then I shut engine off and restarted without pumping brakes. ABS indicator this time lighted for maybe a second and then went out.

Incidentally, when I first depressed the brake pedal during the test of twelve pumps, the pedal hit a resistance point at maybe halfway and then proceeded to the normal level for braking. This is what it does when pulling to the left as well. If pulling to the left, I can depress harder on the brake pedal and "push through" and the brakes will work fine for a while.
Gerry

 

Here's another Pic that didn't transmit. Sure appears to be a mirror twin to your's.
Now what do you recommend?
Gerry

 

Hi Gerry

Your ABS Master Cylinder Actuator looks exactly the same as mine, so that is a good start.

But before you take the Valve Block apart (only 4 nuts Lol) bear in mind it could be something else.

(1) A Stuck/Sticking Caliper (although I believe you said you fitted New ones)

(2) A Wheel Speed Sensor

(3) A Sticking Brake Pad. (especially if you have fitted New ones)

I'm not an expert on Wheel Speed Sensors so your best bet is Warrjon or Videos on YouTube.

As for a Sticking Brake Pad, it could well be that as there can be a slight variance depending on where they are made.

So they may not be a good fit, straight out of the Box.

In which case I always grind a bit off the Top and the Bottom of the Metal Backing Plate, so they slide in and out very easily using only your fingers.



This Brake Pad was such a tight fit that I had to grind 0.5 mm off the Top and Bottom of the Backing Plate, so it would easily slide in and out using only your Fingers.



Grinding a bit off the Top and Bottom of the Backing Plate, so that the Pad would slide in and out using only your Fingers.

First I cannot say for sure that you have a problem with the ABS Valve Block, its up to you and the Garage to determine the cause of your Braking Problem.


Also there is no Guarantee, that this Fix is going to Work as a lot depends on how bad the Valves are inside.

(or whether the Valve Block was the cause of the problem)


So when you've tried everything else you can think of, then you can try this.


I'll give you the Shortened Version First to give you an idea of what to do.


(1) Remove the ABS Master Cylinder Actuator (including the Brake Pedal as one unit)


after De-pressurizing the System and draining all the Brake Fluid out of the Reservoir.


Apart from undoing the Brake Pipes on the Unit, there are only 4 Bolts holding it in.


Have lots of Towels and Soapy Water at the ready because Brake Fluid could run everywhere (even when the Reservoir looks empty)

Don't let any Brake Fluid drip on the Paint Work, or it will destroy it in an instant!

(2) Once the Unit is out of the Car, lay the Master Cylinder Actuator on its side so that the Valve Block is Facing Upwards.


(3) Before you take the Cover Plate off, you need to know what you will find inside.


Which will be 6 Steel Valves joined to the Plug on the Side with Ribbon Connectors.


These Ribbon Connectors are so Fragile, that even touching one could break it off.


So having Very Carefully removed the Cover Plate, you may find that one of these Ribbon Connectors has Broken off from one of the Valves.


If so that's your problem right there!



But before you touch anything, do a drawing of how these valves are Wired into the Plug. Double Check It: DO NOT GET THIS WRONG! for obvious reasons.


The Valves themselves lift out and will need to be Cleaned in an Ultrasonic Cleaner


On the Assumption you don't have one, take them into a Jeweler and ask them to clean them for you, as that's what they use to Clean Jewelry.


Dentists also use these as well, so you could take them there and ask a favor.


Having got the Valves Clean, take the Valve Bock and the Valves into a Radio Shop with your drawing and ask them to Re-Wire the Valves into the Plug using Wire.


In other words get rid of the Ribbon Connectors and use Wire instead.


Obviously you could do this yourself but you need to be Ace at Soldering, as if a Wire comes off then its 'Game Over'


So best to leave this to the Guys who do this every day and know what they're doing.


Then after reassembling, basically that's it!


And then just a question of refitting the Unit and Bleeding the Brakes.


Before you remove the Master Cylinder Actuator, there are some Electrical Tests you can do, which are outlined in the longer version.


Which is here: https://www.jaguarforums.com/forum/x...photos-140828/

 

I appreciate your advice...looks like work ahead.
Fortunately this car is a play car and is seldom driven...that in itself may be the problem, but it can be under repair for a while with no problem.

I haven't really checked this out but are you saying that by removing four bolts in the engine compartment the entire assembly, including foot pedal can be removed outward through the firewall?

This may be a time when education and experience in my very early career will be beneficial. I'm not worried about performing the soldering as I was a licensed commercial broadcast engineer years ago and built about twenty Heathcraft projects including a color television that required hundreds of non-cold soldered terminations. Also, I still have most test equipment stacked away somewhere.

I doubt if it's the calipers or pads. I replaced both front calipers early on in this saga. Had planned to replace pads but the parts house shipped the wrong pads so I installed the old and they fit well. Also hoses were replaced on the front. This is an intermittent issue.

When this didn't fix the problem I took the Jag to a commercial shop. They replaced the right front caliper again...still no better.

That brings me up to date and have suspected for a long time that a proportioning type valve must be the issue.
Again, thanks and will report back after getting this in the que for priority.
Gerry

 

When the pads were replaced, was a tiny bit of anti seize used on the places where the pads contact the caliper? I'm wondering if the pads are binding in the caliper.

 

My '95 was ripping the wheel out of my hands at low speeds after a wheel bearing job. I either tightened or loosened the bearing but which got the segmented metal ring better aligned with the sensor. Maybe give that a try?

 

I read through your point by point detail. Your diary with pictures provides greater detail than one could hope to find, another example of the dedication of many and value of the Internet.

Your concerns with brake fluid damaging the finish is well documented. That should obviously be an overriding caution.

As I live in a rural area, I might benefit by securing in advance the parts that are normally required to perform this repair. If I were to make a list of parts needed it would seem to include:

O Rings for seating ABS block to master (dimensions, material?)
Silicone Gasket sheet for mounting assembly to firewall (Thickness/Amazon)
Sealing grommets for reservoir? (required or reuse original? Normally available at dealer or?)
Any others

If you recall specifications on these or other parts to have on hand it will be helpful. In doing research, it seems ultrasonic cleaners on Amazon and Ebay are reasonably priced. May buy one because it would often be handy if they really work as advertised. Don't know what chemical or if water is best.
Gerry

 

Hold on. That is an important clue. If I had to bet, I'd say you are most likely looking at a wiring issue from one of the wheel sensors, rather than a valve block or other typical cause of brake pull.

 

Hi Gerry

Once you've undone the 4 Nuts that Bolt the Master Cylinder Actuator to the Fire Wall, the whole lot including the Brake Pedal, lifts out from

under the Bonnet/Hood in one piece.

Don't unbolt the Reservoir from the Master Cylinder Actuator because.

(1) It gives you something to get hold of to 'Jiggle it out'

(2) Less chance of Brake Fluid going all over the place, which would happen if you took the Reservoir off.

(3) No need to replace the rubber seals, much better to leave the originals with it all bolted in place.

(4) You can take the unit out in under a hour and you don't even need to remove the Air Cleaner.

The 'O' Rings are no longer available, at least in the UK so if you are very careful you can reuse the originals when you take it apart.

DO NOT use anything like White Spirit or Paraffin for Cleaning. USE Brake Fluid or you could melt the 'O' rings.

No need to buy any Silicone Rubber, make a Firewall Sealing Gasket out of the Smooth Side of a New Hot Water Bottle.

That was what I used when I did this job on another XJS and it was better than the one that I had Laser cut out of Silicone Rubber.

The Smooth Side of a New Hot Water Bottle is just the Thickness you need for doing this job.

Don't bother buying an Ultrasonic Cleaner, as the DIY versions are not up to the Job.

Jewelers and Dentists use the industrial type as the DIY versions won't touch it.

So basically there is nothing to buy except a piece of wire and some DOT4 Brake Fluid.

Have a look at the Photo of one of the Valves, if that microscopic hole gets blocked from something like a grain of rust carried in dirty Brake

Fluid, then it can Spin your Car right off the Road and the same goes for a Broken Ribbon Wire,









Rust caused by Water in the Brake Fluid which needs to be renewed on a regular basis.

One of the things you must NEVER DO when replacing the Front Brake Pads, is to Lever the Pistons back in the Calipers without having the

Bleed Nipples Open.

Because if you send Brake Fluid the wrong way up into the System, this can be 'The Kiss of Death' for the Master Cylinder Actuator, for which

there are No Spares.

Worst case Scenario, you may have to get a S/H from a Breakers but hopefully you should be able to fix it.

But Check the Wheel Speed Sensor First, as it could be that as has been said.

 

Thanks for all the assistance. Won't be able to dig into this for a week or two. The reason I doubt the wheel sensors is that the issue returns when stopped for a while or even if driving and not applying the brakes for a half hour or so.

That said, is there a test procedure for the wheel sensors if it comes to that? If that's the issue then it would seem possible a wiring issue exists anywhere from the sensor to the controller and possibly in the sensor itself.
Gerry

 

I don't think it's the sensors, but rather the wiring from the sensors. Due to the exposure to extreme conditions and movement, the wire insulation can become brittle and crack or lose some elasticity that puts strain on the interior wire. It is a common failure of ABS systems. It is also a likely cause of an intermittent issue.

 

Orange Blossom....haven't yet begun tearing our "94 down to check the block as you've detailed but did obtain a "spare" ABS valve block only and already had a used full pedal/master/ABS valve block also shipped.

Today I decided to check out the "spare" ABS block and opened it. One trace lead of the ribbon to what I have numbered #6 is broken...all solenoids click when energized with 12 VDC. Rewiring seems to be straightforward and will attack that when I pick up some wire. Want to be sure I have a 40 strand, silicone insulated for high heat and only have household on hand.

I don't want to damage the circular screens located beneath the solenoid valves. They didn't pop out with a gentle pull, how are they retained or what is the trick, or should they be left alone? I'll attach a couple pics.
Thanks for all advice.
Gerry

 

Hi Gerry

That Valve Block looks in great condition (Nice Find!)

Those Ribbons go 'Crispy' with all the heat and as such would only take a little jolt to break them, as you have seen for yourself when you opened it up.

As for getting those Filters out, I very carefully hooked them out with a Watch Makers Screwdriver but if mine had looked as clean as yours.

Then I may have been tempted to leave them alone and just run some Brake Fluid through them, so its your call on that, except whatever you do don't damage them.

Having looked at those Photos, I'm very Tempted to say that unlike on my V12 Car you have a lot more room to work around the Master Cylinder Actuator than I did.

So if you are very careful, then it looks like it 'MAY' be possible to just replace the 'Valve Block' without taking The Master Cylinder Actuator out of the Car!

The only thing to watch out for is those Big Valves falling out under their own weight as well as not losing the rubber sealing strip gasket for the plug.

I definitely think you can do it this way, which would be a lot better, than Tearing everything down as you seem to be a Guy who knows what he is doing.

So its gotta be worth a Shot.....

Just watch out for 'Paint Destroying' Brake Fluid running everywhere, so pack plenty of Towels around where you are working and if they get any Brake Fluid on them.

Pull them out from under the Car, rather than risk a single drop dripping on the Wing/Fender or Engine Compartment.

 

Thank you. The valve block was overall very clean externally and with no rust whatever on the steel valve bodies. In testing the solenoids with 12 VDC, I may have inadvertently shorted a trace circuit, causing the open to that solenoid. I wasn't concerned because the plan was to rewire anyway.
Your cautions concerning brake fluid are well noted and cause me to think of possible preventative measures. One, I may position plastic sheeting and mask the entire firewall and fender areas, regardless if I remove the master assembly or only the ABS valve. I agree that removing the ABS only doesn't appear to be too challenging on the "little" six. When I ordered the car, it just didn't seem worth the added cost for the V-12 which would seldom be called on. Then after taking delivery I soon wished for the 12....now again maybe not so much.