I have an 87 XJS which I rebuilt into a race car. The ABS accumulator/motor does not work. I have brakes but have to stand on the pedal to try and stop the car. Is there anything else I can do to replace the system to get brake boosting?

 

Hi TWR Replica

The First thing to Check is the Fuse, which if you haven't stripped the Car out will be located under the Knee Panel on the Passenger Side.

There are a lot of Fuses in there but the Two that operate the Brakes are grouped together on their own and as such will be very easy to find.

One of them is for the Brake Pump and the other one is for the ABS.

So how come you've got any Braking at all?

The Front Brakes and the Rear Brakes are like two different Systems working in Tandem.

Which also has a Built in Safety Feature.

So in the event the Brake Pump Fails and Stops Working, Blown Fuse or Whatever.

The Front Brakes which are Conventional 'Should' still Stop the Car.

While the Rear Brakes Must have the Pump running.

Don't rely on 'The Jaguar Gods' don't drive the Car until you've Fixed the Problem.



These are the Fuses for the Brakes under the Knee Panel on the Passenger Side.
In a small compartment with a drop down panel and a turnbuckle to open it with a coin.
One is for the Brake Pump and the Other is for the ABS and each one is Clearly marked on the drop down Panel, so you know which ones which.

 

Since you're racing... I've got a wining formula for you...

1. Replace the whole pedal assembly with a vacuum booster and traditional master cylinder from a PRE-ABS car. You can also use a later pedal / booster assembly from a 95/96 when Jag went back to traditional vacuum brakes. The later style are nearly impossible to find here. The Teves MK2 system you have now has no mechanical connection to the rear brakes and thus very poor feel. IMHO it has no place in racing.

* With an early booster You can use Mitsubishi aluminum M/C for more reliability and to save a few pounds. Either way you can upgrade to a 1inch bore MC as Jag did on 96/95 MC or when using the Mitsubishi MC

2. Replace the rear inboard brakes with hubs/spindles and vented outboard brakes from a X300. This will effectively over brake the rear which can be modulated with a Wilwood proportioning valve.

3. Install a 2lb residual pressure valve on the rear circuit.

4. Plumb proportioning valve inside the cabin and tailor your brake bias to the track conditions. If there are long straights for breaking you can increase the rear bias, carry more speed and brake later. If you need to brake on a sweeping corner or if the track is slick for some reason... you can decrease the rear bias and decrease the chances of a spin.

Follow these steps and you will have a faster, safer, more predictable race car. With a 1 inch bore, 2lb residual and a good racing compound you'll have Porsche like feel and response.

 

XK8-XKR 1996-2004 Brake booster, pedal, master cylinder easy fit with little mod.

 

So i got a 89 jaguar xjs
brake pedal goes down to the floor, spongy,
i have tried bleeding brakes conventional style on the front, but i am not getting very much fluid out,

what is the proper procedure to bleed the brakes, im thinking i still have air, or something is clogged up,

i recently change th accumulator, pump runs fine and shuts off after build up, rear brakes there is fluid coming out no air, but when i put the car in drive and push pedal down you start to hear pump activate but it does not stop the car,

im puzzled, if someone could give me a suggesting on what to do or maybe have any idea of what it may be

 

Hi Jonathan

Before you are able to bleed the Brakes, you need to Bleed the Low Pressure Side of the System especially if you have either let the Reservoir run dry or replaced any components as you say that you have done

This is the Pipe that travels from the Bottom of the Reservoir to the Brake Pump, where you will see a little spring clip that needs to be pulled out and then once having done that, you need to pull out that little Plastic Elbow from the Brake Pump

And then let the Fluid Run Free till the Air is all out and then as soon as you have done that, put the Plastic Elbow Back and then replace the Clip ( and then Bleed the Brakes)

In other words you have to Bleed the Low Pressure Side of the System 'On the Fly' with Brake Fluid flowing out under gravity but do not let the Reservoir Run dry, or you will have to start all over again

And DON'T get any Brake Fluid on the Paintwork of it will strip it in an instant and really spoil your day if not your life!

Also the is a 50/50 chance of Breaking that Plastic Elbow and it could be hard to find another one

The Full Procedure is explained here on Page: 19 of my 'Cherry Blossom' Restoration thread

Bleeding the Low Pressure Side of the Teves Master Cylinder Actuator and Bleeding the Brakes on my 1989 and 1990 XJS V12

 

I have done that already and i just did it again, there is a stream of fluid coming out no air bubles at all

the problem is the pedal is not getting hard at all like everyone says,
should i pump the pedal 20 times before doing the low side bleeding?

 

Hi Jonathan

When you Bleed the Low Pressure Side of the System 'Its Ignition OFF' DON'T! turn on the Ignition until that Plastic Elbow is back in the Brake Pump with the 'Clip on' or Bad Things may happen

Always a good idea to pump the Pedal 20 times before you start

Once you have Bled the Low Pressure Side of the System and Clipped the Plastic Elbow back in place, that's the 'Risky' part over!

But Bleeding the Brakes on an XJS is seldom a 'Walk in the Park' and often needs to be done a couple of times, in as much as you will probably need 5L of Brake Fluid

What makes Bleeding the 'Teves' Brakes a little more Complicated (when compared to a more conventional system) is that when you Bleed the Rear Brakes, you do need to do this with the Ignition ON

While gently Pumping the Pedal to Bleed out all the Air, as you would normally have to do on many other Cars

But........and there's always a But! As you are Pumping the Air out of the Rear Calipers, with the Ignition ON, as you do so the Brake Pump will Start Running to Re-Pressurize the System (as remember the Ignition is ON)

This is fine No Problem, as that is supposed to happen But 2 Very important things to bear in mind

(1) Do NOT let the Brake Reservoir run dry, or you will have to Start all over again

(2) Do NOT let the Brake Pump run for more than 30 Seconds at a time without a 2 minute rest in between Key Actuation's, a Key Actuation being (Turning the Ignition On and Turning it OFF again)

Or you could burn out the Brake Pump (ask me how I know or rather don't)

So Bleeding the Rear Brakes is often a Stop and Start process

As you don't want to run the risk of that Brake Pump over heating or running dry and burning out

Think of the Front and Rear Brakes as being Two Separate Systems working in Tandem because unlike the Rear Brakes, you can Bleed the Front Brakes, in 'Almost' the same way that you might do on any other Car

Except of Course its an XJS where unlike many other Cars it has its little 'Quirks' which are often referred to as interesting design features (Doug D.)

So although you Bleed the Front Brakes in 'Almost' the Conventional Way (This time with the Ignition OFF)

This process requires a certain amount of 'Free Styling'

In as much as when you Bleed the Front Brakes, you do need to Occasionally Turn the Ignition ON in order to re-pressurize the System (for no more than 30 seconds without a 2 minute rest in between Ignition Key 'Actuation's' as already described)

But having said that, you could if you wanted to, leave the Ignition ON all the time!

'How come so?'

The Very Important difference here is leaving the Ignition ON all the time

Is NOT the same as having the Brake Pump running all the time (which is a most definite No! No!)

As with the Ignition ON all the time when Bleeding the FRONT BRAKES the Brake Pump will only cut in to Re-Pressurize the System as you Pump the Brake Fluid through the Calipers with the Pedal

Although which ever way you do this, do not let the Brake Pump run for more than 30 Seconds, even if you have to turn the Ignition OFF in between

If in any doubt at all then do it the first way described

But trying to Bleed the Rear Brakes without using the Key, would be like trying to nail a Jelly to a wall

Also on No Account attempt to Change the Calipers (if you ever have to) without the Bleed Nipples open, as if you send Brake Fluid the wrong way up the System towards the 'Master Cylinder Actuator'

That could be a 'Very Expensive Mistake!'

In the event that none of this helps, get back as its not 'Game Over' there's lots other stuff that we can try

 

So i tried the procedure, no luck
so what happening is that when you apply the brakes it actually engages and then it releases the brakes, allowing it not to brake
sometimes the pedal will get hard and brake, but it releases right away, it doesn't keep everything locked up.

Im pretty sure there is no more air in the system as i did what you recommended me to do.

What next?
Pump, valve block or master cylinder

 

Hi Jonathan

First of all can you confirm that this is the type of Master Cylinder Actuator that you have in your Car




Teves Master Cylinder/Actuator

When you say that you Changed the Accumulator (Black Ball) did you replace this with a 'Brand New' One?



The 'Accumulator' Black Ball

When Stationary with the Engine Running, how many times can you Pump the Pedal before the ABS Light comes on?

Has the Car ever 'Violently' Pulled to the 'Left' or 'Right' when Braking Hard?

Have you checked for Sticking Calipers and or Brake Pads?

Just trying to eliminate the most common causes, before getting into fixing the 'Master Cylinder Actuator' in case of a Broken Wire or a Stuck Valve

You've said the Brake Pump is running and that being so can then be eliminated as a possible cause of being the problem

Have you 'modded' the Brakes in any way and have you Checked the Two 30 amp Fuses under the Knee Pad on the Passenger Side.

One is for the Brake Pump and the other one is for the ABS

Any unusual events occurred from the last time the Brakes worked ok

 

My system has the black connector on the pump, but yes the accumulator was replaced, not the pump

no pulling that i know of, just spongy brake pedal that goes down,

i have done the fallowing:
New pads/ calipers, rotors on the rear of the vehicle (not fun to do)
new pads and rotors on the front of the vehicle, (did not replace calipers, also i release the bleeder before pushing calipers back into original position.
(when i bleed the front brakes, sometimes i get a good amount of fluid, sometimes it just drips)
I replaced a the master cylinder from JAGBITS, suppose to be a rebuild one, but who knows,

fuses are okay, on passenger side,

calipers are not sticking i can rotate tires, but if i try to use the brakes it engages and then it looses pressure,
I did move the front calipers brake lines ( you think they might be kinked) and would that cause low pedal or spongy pedal or no brakes?

 

Hi Jonathan

If you replaced the Master Cylinder Actuator (ie the whole unit) then that does sound quite unlikely to be the cause of the problem, as too does the Brake Pump or Accumulator (Black Ball)

Much more likely to be those 'Kinked Brake Pipes' that you mentioned, that could be holding the Fluid Back to give you a False Sense of Security that everything is OK and then Slowly releasing it on the way to the Calipers

To give you a sort of 'Stop and Start' feel to the Pedal as you try and apply the Brakes

The one other thing that it could be is the Rear 'Flexy Brake Pipe' to the Rear Calipers, which is a Total PIA to get off most of the time, as if not renewed then these have been known to Collapse from the Inside

Which could obviously then hold back the fluid but since you said that you were getting Brake Fluid without Air from the Rear Calipers, if I understood that correctly?

It really does sound like those 'Kinked Brake Pipes' could be the Cause of the Problem and are relatively speaking inexpensive to renew in the scheme of things

So whether or not it is the cause of the problem, it seems worthwhile to replace them with New ones anyway, as when doing any work on the Brakes, you need to have a solid foundation to start from and so that is the job I would do first

Well done for the work you did on the rear Calipers, as I have also heard its a PIA Job

Fix the Pipes and then come back and let us know how you get on

 

just an update- i ended getting a new master cylinder with abs pump rebuilt- and also installed a new motor pump - i did the whole procedure to bleed system ( finally got a got pedal)
now the jaguar stops !
But i do have one concern, i notice that when i am at a stop light, the pedal seems to sink in slowly ( is this normal)

if you sit there for about 5 minutes it almost goes al the way to the floor.

Do you believe i still have some air in the system or is that normal to sink very slowly to the floor

 

Hi Jonathan

No, that isn't supposed to happen, the pedal should be hard with almost no give and stay that way until you release it

Did you replace those 'kinked brake pipes' you mentioned?

Are you sure the Calipers and/or the Brake Pads are not sticking?

Maybe there is still Air in the System?

If you fitted a New/Recon Master Cylinder Actuator, it would have been a good idea to 'Bench Bleed It' before you put it in and then Bleed it again after fitting

If there is anything wrong with the Calipers or Brake Pads, if so then you will never be able to get the Brakes working, so Calipers/Brake Pads/Brake Pipes is always the Best Place to Start

Brake Pads do not always fit straight out of the Box and you should be able to slide them in and out of the Caliper, just using your finger and thumb (when the Caliper Piston is not pressing against them) otherwise Brake Pads can and do stick

So what I do is to shave a few thou. off the edges of the Metal Backing Plate of the Brake Pads (not the actual pads themselves) so I know they won't get hung up and jam and I also always put in new Fitting Pins

You can see how I do this including Photos, on Page:9 of my 'Cherry Blossom' restoration thread

You must get the bottom end of the Car (Calipers/Brake Pipes/Brake Pads) all done first and then work your way up, or you will never get the Brakes to work

Since you replaced the Brake Pump, did you also replace the Black Ball Accumulator?

As that is what maintains the Pressure or was the Brake Pump also a rebuilt unit?

There are only a certain amount of things that it could be, check for Air leaks where the Brake Pipes go into the Calipers if you have removed or refitted new Brake Pipes

Here is the Link Below:

Making Sure The Brake Pads Don't Get Jammed In The Calipers (Complete with Photos)

 

OB I have a question. 90 ABS brakes system: I redid my brakes; new rotors and pads remanufactured calipers. I should have gotten new flex lines but didn't Anyway my brakes seem to take a heavy foot to operate. I've not driven any other XJS so I don't know if this is normal or not. It sure doesn't brake hard and fast or touchy like a vacuum boosted car...rather it takes more effort than I believe a proper Jag should...??? BTW my ABS is inop as I discovered a short in the main harness but haven't fixed it yet with my parts car harness. (discovered the short after trouble shooting the system after it acted up and pulled hard to the left...the short is in the right front main harness to the sensor pigtail ((not the pigtail itself dangit.)) At least I didn't take apart the ABS manifold (like you had to) before discovering the harness short. Basically I'm asking if it's normal to have to push harder than a "normal" vaccum boost? If not than I'm not sure what the problem is or what to fix...flex hoses?, fix ABS harness and then see? (Maybe I should start a diff thread for this?)

 

Hi Steve

No that is Not Normal, even a very light press of the Pedal is normally all that is needed to slow you down during normal driving, where the only exception would be something like a hard emergency stop

So it would seem you've got a problem with the Brakes that does need sorting out before you go and drive the Car

If the Car is suddenly diving to the left or right, where you feel the Steering Wheel is being snatched out of your hand, then that is usually a sign of a Broken Wire (inside the ABS Valve Block)

Which is a very Cheap and Easy Fix but Only if its gone about the right way, so Don't go pulling the Cover off the Valve Block or else some or all of the Valves could fall out just under their own weight and then you could find yourself in an even worse mess

So first job is to Fix your Wiring Harness, which may hopefully solve the problem but if after doing that you find the Car still snatches and takes a very violent dive to the left or right

Then get back and I'll show you how to fix it but Don't go ripping the Valve Block apart as then we won't be able to see what was the cause of the problem

But obviously only you can fix the Harness or whatever it is that is shorting out or broken

Pulling to the left or right is usually a sign of a Stuck Brake Pad or Caliper which is Not to be confused with a very Violent Pull to the Left or Right, where the Car takes a dive and you feel the Wheel is trying to be Snatched out of your hand

Though if you get a situation where you almost have to stand up on the Brakes to Stop the Car, then that could be the 'Black Ball' Accumulator (although from the way you've described it, then it doesn't really seem like its that in your case)

 

The brakes work including the rear, so the pump and accumulator I think is working. It does not violently pull right or left now because I have the ABS disconnected. I will fix the harness and go from there. New calipers not sticking. I suspected the heavy pedal pressure is not correct.

 

Hi Steve

Even a very light press of the Brakes should be more than enough to slow the Car down regardless of whether the ABS is connected or not (either way you shouldn't notice any difference)

Can you hear the Brake Pump running and does it cut out when the pressure has built up?

If so how many times can you press the Brake Pedal (fairly hard) before the Brake Pump then cuts in again?

If its less than about 5 times, then it could be a loss of pressure in the 'Black Ball' Accumulator, though don't jump to that conclusion straight away, as it could equally have something to do with the problem that you have got with the wiring harness

So best to get everything working, including the ABS and then see where you go from there

What was happening with the Brakes that doesn't happen since you disconnected the ABS?

If the Car was Violently pulling to the Left or Right and trying to ****** the Wheel out of your hand, then unless you are very unlucky its a very easy fix, that shouldn't cost you more than 30 Bucks (So well worth doing)

 

Just a quick thanks for the response...I just haven't had time to get to it.

 

I know it was an old reply, but I am wondering what mods are needed, and does it still need the accumulator ball and pump to work?