Having removed and then replaced the Actuator and Valve Block on my XJS V12 The next job was to bleed the Brakes.

Where I understand that in this case first of all you have to Bleed the Air out of the low pressure side of the System@PTJS

As I was having all sorts of trouble either getting the Brake light to go off or to come on, where at one point I was thinking that I'd burnt the motor out, that hasn't happened yet but there's still time!

I can see there is a Braided Pipe that goes into the Pump with the Black Ball, which is held in place in the end of the pump with a pin that has a ring attached to it.

I managed to get the Pin out Ok but I couldn't get the elbow 'thingy' to come out of the pump, I wasn't trying too hard as I didn't want to break it but does it just pull out?

I did take off the other end of this Braided Hose (that has a hose clip on it) and loads of brake fluid came out, which was what I was hoping for and expected.

But as I am having a problem, getting the Air out the Brakes, I'm thinking I'll get nowhere, unless I can get the other end of the Braided hose out of the pump, that's the end that is held in place with the Pin with the ring on.

Any tips on getting the end of the Braided Hose (held in place by a pin) out of the Pump motor.

 

OB,

It just pulls out. But you then ought to discard and change the O-ring as the manual says. This comes as part of the seal kit JLM1477 still available from Jaguar.

How about spending a few extra quid whilst you're there and buying the service manual? Based on all the work you do on the cars, it will save you hundred of hours effort and sleepless nights!

Good luck

Paul

 

Hi Paul

Glad you replied, do you reckon this is why I am having a problem in getting the Air out of the System.

I thought that undoing the end with the hose clip, might just be enough but now of course I'm thinking I was wrong.

The only good news is the Brake Light came on and then went off again after about 30 seconds.

But the Pedal is still very spongy, as although I've bled it several times, there must be air still trapped in there somewhere.

Which I think you identified as that low pressure hose, so hopefully if I can pull that pipe (with the pin) out, then that might solve the problem.

You are right of course about the Manual but this Car is a 'Cash Cow' that continuously needs a shed load of money spent on it.

 

Hi OB,

The XJS ABS system is a fascinating bit of kit (sad of me, I know!). I'm intrigued by the mind that designed the complex action of the actuation unit!

My naive understanding of the system makes me think that the accumulator wouldn't be able to build up to its c180bar if there was any air on the low pressure side. But I might be wrong!

The soft pedal is difficult to diagnose because of how the system works. Because the pedal doesn't "push" the fluid to the rear brakes, my initial thought was that you couldn't have air in the rear circuits. But I now think that isn't necessarily true. If there was air in the first (actuation) part of the boosted rear circuit, it could allow the pedal to move further forward than expected. And air in the static front circuit could also allow a soft pedal.

So, although I don't THINK that you've got air on the LP side, I would still bleed it. Then I would bleed both rear and front circuits. Use the EXACT Teves procedure and do Rear then Front. Always keep the reservoir topped as you can get through a lot of fluid. And when you do the rear, use the full 15 seconds of pump operation in case the air was in the actuation assembly at the outset. Remember to let the system repressurise in-between wheels.

See how it is after the first cycle of bleeding and be prepared to do it twice.

Good luck

Paul

 

Hi Paul

This is what happened.

When I tried to bleed the Rear Brakes, there was an almost continuous stream of Air Bubbles in the Brake Fluid.

So picking up on what you said, I knew that the 'Thingy' held in with the Pin had to come out.

Although I could rock it 'to and fro' it just refused to budge, Mole Grips wouldn't pull it out, or levering with a Screwdriver, it was stuck fast.

But in the end I did it with a full sized Crowbar, obviously being as careful as can be!

Though just before I disconnected it, I was well aware that there would be Shedloads off Brake Fluid, pouring out of it.

So instead of stuffing rags everywhere, which I knew were going to get soaked, I got myself some baking foil (it was reinforced damp proof stuff) but same difference.

And then I fashioned a Channel out of it, a bit like you see at Water Parks only this was a little bit smaller.

Then when I pulled out the 'Thingy' A River of Brake Fluid, flowed down the Channel and poured in a bowl that I had put under the Car.

Not a single drop of Brake Fluid, went anywhere except there! 'Ingenious or What!'

Then with the Car Jacked up in the Air (well supported everywhere) so that it couldn't fall.

I put a Bleed Tube on one of the Rear Calipers, then sat on the Sill without touching the Brakes and turned on the Ignition.

Brake Light 'ON' - ABS Light 'ON' at which point I counted to 30 by which time the note of the Pump has started to change (it went much quieter)

With the Brake Light and ABS Lights still on, I switched off the ignition and looked at the Brake Fluid catching Jar, that I had put under the Car, with the Tube from the Bleed Nipple dipping right down into it.

Which was already open, half a turn.

At this point there was no Fluid in the Jar at all (surprisingly to me)

So I put my foot on the Foot Brake and held it down (Ignition Off)

As soon as I did so, I could hear a 'Buzzing Noise' coming from the Pump, even though it was totally switched off.

Then about 10 seconds later, the Brake Pedal started to push upwards, all on its own.

Then as I looked in the Bleeding Jar, I noticed there was lots of Brake Fluid in it and no sign of any Bubbles in the Tube.

So just to be sure, I rinse and repeated this about Six Times (though three would have been plenty)

And then did exactly the same to the other rear Caliper, which gave me exactly the same result as the first one did.

Then I Bled the Front Calipers in the Conventional way, the same as you would do on a normal car.

After which I Turned on the Ignition, with the intention of letting the Pump run for no more than 60 seconds (as I've heard they can get hot and then burn out)

But by the Time I had counted to 40 The Brake Light Went Out and so did the ABS Light.

Leaving me with the hard Brake Pedal I wanted.

I have no idea at all if this is the way that you are supposed to do it but it seemed to work for me.

And as for the 'Teves Brake System' I for one am not intrigued and still don't fully understand, how the thing works.

Although I do know what can happen, when it decides to go wrong!

So now I'm off for a Test Drive! (Wish me luck!)

Channel fashioned out of Damp Proof Coursing (You could use Tin Foil) so the Brake Fluid, can run out of the Car to be caught in a bowl underneath.

 

OB,

Sounds like good progress and well done for not drenching the engine bay in brake fluid!

However, you should bleed those rear brakes the correct way, which is using the pump and accumulator to push the fluid and air to the rear brakes. The design of the system is such that pressing the brake pedal allows the valve to open from the accumulator. The pump then pushes the fluid to the rear brakes. It sounds that the way you've done it, the pump has not been driving the fluid and air because you didn't have the ignition on when you used the brake pedal to open the valve in the actuation unit. I think what you've done is just let the accumulator use some residual pressure to try and push fluid and air. Because of this, you're not using pump pressure to push fluid and air to the rear. (It doesn't matter how hard you press the brake pedal, that's not moving any fluid to the rear!). The correct procedure is as follows:


TURN ON IGNITION AND WAIT UNTIL BOTH ABS AND LOW PRESSURE LIGHTS HAVE EXTINGUISHED AND ALSO THE MOTOR PUMP HAS CUT OUT.

THEN, OPEN REAR LEFT BLEED NIPPLE AND HOLD BRAKE PEDAL DOWN, WITH IGNITION ON FOR 15 SECONDS – NO MORE

TIGHTEN BLEED NIPPLE, TURN OFF IGNITION, RELEASE BRAKE PEDAL.

WAIT ONE MINUTE AND REPEAT FROM RESTORING SYSTEM PRESSURE AS ABOVE FOR OTHER NIPPLE IF FITTED.

THEN WAIT ONE MINUTE AT LEAST BEFORE MOVING TO FRONT BRAKES – THIS PREVENTS THE MOTOR PUMP FROM OVERHEATING.

AT THE FRONT, ENSURE SYSTEM PRESSURE IS CREATED AND THEN BLEED CALIPERS CONVENTIONALLY WITH IGNITION ON, USING SLOW STROKES AND GO THE FULL TRAVEL BUT DO NOT FORCE.

ONCE THE LEFT SIDE HAS BEEN DONE, AGAIN WAIT ONE MINUTE AND THEN RESTORE SYSTEM PRESSURE.


This means that the pump drives the fluid and air when you bleed the rear circuit.

It also means that the pumped fluid ensures you have boost pressure providing 4:1 assistance acting on the master cylinder circuit when you bleed the front brakes.

Paul

 

Hi Paul

I had no idea you were meant to do it like that and you are right in that I was using residual pressure.

But even so it seems to have worked at least for me to take her for a Test Drive.

So I'll let you know what happens after that.

There wasn't a Single Bubble of Air, anywhere to be seen so I don't think there was any way for me to improve on that.

Though maybe the 'proper way' could be much better and quicker, its only taken a couple of days so far!

 

Hi Paul

I'm back in the Game! and the 'Test Drive' went without a single hitch.

I think it would be fair to say that I was very nervous but the Truth was I was really 'Brickin it'.

And kept pulling over in Lay By's to check on the Level of Fluid, which just stayed the same.

No sponginess in the Brake Pedal, from what I was able to tell but I've been off the road so long, that it was quite hard to remember what is was like before.

Also I kept my Speed right down to about 50/60 mph and avoided overtaking anyone at all.

So its going to take a bit of time to get my Confidence back after such a big scare.

The problem being 'The Cats got Nine lives' and I have used up Four of them already!

When the road was clear of Traffic, I did a few emergency Stops and She pulled up straight and true, although at one stage, there was a 'click

clicking sound' which may have been the ABS cutting in?

This was a different rebuild from the ones I've done before but I need to make sure that its working OK before I go into details, of what I actually did.

While I didn't bleed the Brakes by the Book, in the way you are supposed to, could you see anything inherently wrong, with the way I did it?

Everything is working well and the ABS and Brake Light, both go off within seconds of Starting up.

In any event, I managed to get home in one piece!

 

OB,

It all sounds really good news! Well done!

I absolutely understand how you will have felt after the recent problems. As with many other things, confidence is something that builds up subliminally over time but can be shattered in a second! Each subsequent successful drive will build your confidence and whilst we all hope you'll never need to rely on your ABS, if it does happen successfully, your confidence in the brakes will build immeasurably.

I know you've had your setbacks, but I do admire the Teves system. Coupled with Jaguar's over-engineering of the front brakes should mean that brakes are one of the best bits of an XJS.

As regards your bleeding procedure? You've bled the rear with residual rather than pumped pressure. And you've bled the front without boosted assistance. However, if you've got a firm pedal, a good fluid level, no warning lights and a pump cutting out soon after startup and not running a lot during normal driving, then I think you should be ok.

Try and remember how the pedal feels and be aware of any change each drive. Also, try just letting go of the wheel during some gentle braking and note any pulls to one side. Also get in the habit of looking at the discs periodically to see if all the discs are being wiped fully and cleanly by the pads. I do this every time I drive the XJS, but I do have outboard rears which makes it more convenient.

I really think you're there. Good perseverance! Now lets's hear about some great drives to the coast and those fish and chip suppers!

Cheers

Paul

 

Hi Paul

Thanks

And I think it is worth mentioning, that without your insistence that I pulled that plug and bled the low pressure system, I would still be 'limbo dancing' under her right now.

There were so many bubbles in that tube, that I thought something I did must have been leaking.

But as soon as I bled the low pressure side, all of those Air bubbles suddenly disappeared.

When I'm driving I'm keeping my distance, as I always do and testing the brakes well in advance of needing them just in case.

But when you get the grey matter working, here's a Question for you.

Can the ABS tell the difference between a Mechanical Failure and an Electrical one?

As if not then it could be its Achilles Heel.

Take a look at the Pic of one of the Valves that I have taken out of the ABS Valve Block.

Which I doubt that many owners of the XJS have ever seen.

If you get your magnifying glass, you may be able to see a very tiny 'pin sized hole' in the centre of the Valve.

This is the big danger, of replacing the Brake Pads the incorrect way, by levering the Pistons back, without clamping the Brake Pipes and leaving the bleed screws open.

As in not doing so, it may force fluid the wrong way up the System, where it only takes a small amount of Contaminated Brake Fluid (dust/grit) to block up that hole.

So when the ABS cuts in, it could be that this valve isn't working, which may be what happened to me, when my Car took a dive to the other side of the road.

Knowing this can happen, really tends to concentrate the mind, as there isn't any warning whatsoever.

 

I would like to ask for a little more explanation on how to bleed the low side. I've been trying to bleed the Teves system several times, but I may still have air on the low side. Can I just remove the plastic elbow gong into the pump, then let the air out?. or do I have to bleed the pump/accumulator?
Still spongy after following the above procedure for bleeding the brakes. Once I let all the accumulator pump fluid out the rear bleeder for 15 seconds, I had my wife turn off the key and proceed to manually pump/hold, I loosen and bleed, repeat, there was a LOT of air, and the pedal went ALL the way down each time. I then tried the above procedure again, still spongy.

 

Hi mkinn

Yes that is correct, you just pull out the Plastic Elbow and let the Brake Fluid run free until all the Air Bubbles are out and then you push the Plastic Elbow back in the Pump again, while the Brake Fluid is Still Running and then put the Pin back (Ignition OFF) at all times

Then after you have done that Bleed the Brakes, with the Key on to do the Rear ones but don't let the Brake Pump run for more than 15 Seconds at a time without a Two Minute rest in between or you could burn the Brake Pump out

You can Bleed the Front ones as Normal but you would need to turn the Key on now and again, just to pressurise the system and don't let the Reservoir run out of Fluid or you will have to start all over again, which would be a pain

Please let us all know how you get on as quite a few of the guys on here experience the same problem and are still waiting for the magic bullet

 

just adapt this procedure, the brake systems are very similar

 

xalty,

I'm sorry but that's really not how you bleed the low -pressure side of a Teves ABS system on an XJS!

Paul