Hi, Last fall when I hit the brakes hard on my XJS it would pull to the right and the ABS and BRAKE lights would come on. I replaced the front calipers and hoses, bleed the system and still the same. I drove it that way anyway. Put it away for the winter and then when i went to drive it this spring there is no brake assist and the lights come on every time I hit the brakes. Very hard pedal but the warning lights are only on when I push on the brake pedal. I never here the accumulator pump run. I checked the fuses and relay. The fuse is good and the relay does activate momentarily but the pump never runs. My feeling is the abs module "sees" the correct brake pressure and never asks the pump to run but I am not sure how to know this. The only code is "21" for a main valve in the abs system. Not sure if this is related but the odd thing is the ABS light is not illuminated when the car is running, only when the pedal is pushed and in conjunction with the Brake light and they both go off when i release the pedal. Fluid level is correct. I can't safely drive the car to know what may happen at speed. I have looked around the forum and not found my specific issue? any guidance would be helpful. Thanks, Mark.

 

Hello Mark. In asking you to confirm the following. I regret I'm about to be away a few days so a full explanation must wait or rely on others. However, answers to these 2 questions will shape how and where to proceed . . .

• When you are under way, push on brakes, does the effort required feel normal, more or less than before this issue emerged?

• When you push on brakes, do you hear any unexpected sound eg relay closing/opening in synch with BRAKE warning light coming on/off - especially from region behind central dash, console or passenger area?

Best wishes,

Ken

 

Hi acauto

It could be any number of things that are causing your problem, which have to be worked through in a systematic way.

(1) Before you Bled the Brakes, did the Reservoir ever run dry and if so did you firstly bleed the low pressure side of the System.

(2) What procedure did you use for Bleeding the Brakes.

(3) Did you have the Ignition on when you Bled the Rear Brakes.

(4) Did you ever let the Brake Pump run for more than 30 Seconds at a time? If you ran it for more than a minute. You 'MAY' (only may!) have burnt out the Brake Pump.

(5) Where was the Fuse located that you checked.

Pulling to the Right could indicate a faulty Wheel Speed Sensor but also a Blocked Valve or a Broken Wire in the Valve Block.

But if needs be we can get into that later, as there are no Spare Parts Available to fix it, though rebuilding it is easier that replacing all the Spark Plugs.

If thats any consolation.

 

Wow! thank for that rapid response with intelligent questions. Let me address last falls experience first. Brake assist felt normal before and after the front brake work. I only bleed the front brakes as I always have normally done, ignition off, not running. The reservoir never went empty. I did not touch the rear brakes. Now onto this years problem.

The pump does run when commanded by the relay. Initially only momentarily when the key is first cycled. I had an assistant today and with him hands on the pump and very close we determined the pump runs every time I hit the brakes and as long as I am on the brakes. Still no assist.

I am suspecting a failed accumulator ball but am puzzled as to why it does not run the pump all the time but only when I am applying the brakes?

Thank you.
Mark

 

Hi acauto (Mark)

You absolutely have to Bleed the Rear Brakes as well as the Front Brakes, every single time you Bleed the Brakes.

Why? Because if you don't Bleed the Rear Brakes (Every Time!) then you will still have Air in the System.

This is why you can hear the Pump Running, when you hit the Brake Pedal, because as the Air you don't think is there gets compressed.

The Brake Pump cuts in to (Try and fill that air pocket with Brake Fluid) then when you release the Brake Pedal, the Air then sends the Brake Fluid back again.

And waits until you hit the Brake Pedal again when exactly the same thing happens over and over.

So the First thing to do is to Bleed the Rear Brakes.

One Person in the Car and one underneath with the Bleed Tube and Bleed Nipple Spanner.

First make sure the Car is chocked up Safely, so it can't fall on your mate.

Do NOT under any circumstances Start the Car!

Ignition on Does NOT mean Start the Car!

Do NOT let the Reservoir run out of Brake Fluid or you will have to bleed the low pressure side of the System, which needs to be avoided as that come with its own set of bad Gremlins.

Assuming your mate is under the Car, with the Bleed Tube and Bleed Nipple Spanner, you need to start with the one furthest from the reservoir, on a (UK) Car its passenger rear, then drivers rear.

Now Turn on the Ignition and listen out for the Brake Pump Running and also for it to Stop Running.

Do NOT let the Brake Pump run for more than 30 seconds before it stops, without a 2 minute rest in between Ignition ON Actuations or you 'Could' Burn the Pump out (Expensive!)

When the Brake Pump stops running within 30 seconds, unless you have to actuate it for a second time.

Ask your mate to open the Bleed Nipple (the one furthest from the reservoir) after putting the Bleed Tube on (only undo it a quarter turn no more 'unless you really need to')

You should STILL have the Ignition ON but the Brake Pump won't be running, as it will have stopped running within 30 Seconds.

Now with the Bleed Nipple open the minimum amount, Slowly push the Brake Pedal all the way down (which will have the Pump cut back in as you do this and then go off again)

With the Pedal still down, ask your mate to do up the Bleed Nipple and then gently allow the Brake Pedal to come back up.

You may have to repeat this a number of times until ALL the Air is out, then rinse and repeat on the other Rear Brake Bleed Nipple.

Don't forget to keep checking the Reservoir, don't let it run out of Brake Fluid!

Then its on to the Front Brakes, once again starting with the Bleed Nipple furthest away from the Reservoir at the Front.

Strictly speaking UNLIKE THE REAR BRAKES you don't need to have the Ignition on when you do these, as they work on a Separate System altogether.

Its a built in Safety Feature, which means its perfectly possible to have the Front Brakes Working, while the Rear Brakes are NOT Working! (But of course you don't want that)

Although you DON'T NEED the Ignition on, when you Bleed the Front Brakes, I do like to keep the Ignition on, as it recharges the Brake Pump as you Bleed the Front Brakes.

Just don't let it run for more than 30 Seconds between Actuations, without a 2 minute rest in between to allow the Brake Pump to Cool Down.

 

I will definitely bleed the system as you suggest and thanks for such a thorough procedure. That said, the only thing that still bothers me is why the pump only runs for a fraction of a second on start up or just key cycle? Would think it would try to pressurize the system then? And why the assist never improves after I have held the pedal down and run the pump? Maybe the air in the rear has migrated and caused more problems. Not sure how air has been introduced, as the rear has never been opened since I have owned it? Also what changed over the winter?

Thank you
Mark

 

I don't have anyone to help at the moment but I did jack it up and verify the rear brakes are not working at all, so I will start there when I have help.

 

Hi Mark

Its absolutely essential to Bleed the Front and Rear Brakes EVERY SINGLE TIME You Bleed the Brakes, or any Air trapped in the Brake Pipes will sooner or later Migrate.

This is not a job to skimp on, as your Life depends on doing this job properly and if it causes the Car to pull to one side or the other (its usually to the right)

Then you could Spin the Car and kill yourself.

If you don't have a mate to help you, you can do it on your own, with 12ft of Plastic Tubing that fits over the Bleed Nipples and an Empty Plastic Bottle with a Screw on Cap

Drill a hole in the Screw Cap, push one end of the Tube in the Hole that you drilled in the Cap and then feed the Tube into the hole so its an Inch off the bottom.

Then secure the Tube inside the Cap with a Cable Tie.

After that put 2 inches of Brake Fluid in the Bottle, put the Tube into the Bottle so its submersed in the Brake Fluid (but clear of the bottom of the bottle) and Screw the Cap on.

Then put the other end of the pipe on the Bleed Nipple and then Bleed the Brakes, just as if you had a mate to help you.

Which means you will have to keep switching from being IN the Car to being UNDER the Car.

As you Bleed the Brakes you will see the Tube you put in the Bottle Blowing Bubbles as you Bleed the Air out.

You will also need something like a suitably padded piece of wood to jam between the Brake Pedal and the Steering Wheel to hold the Pedal down, while you do the Bleed Nipple UP.

So why do you need 12ft of Plastic Tubing?

This is so you can have the Bleeding Bottle (That you made) Visible while you are sitting in the Car Bleeding out the Air, as you operate the Brake Pedal.

Don't let any Brake Fluid come in contact with the Paint or it will strip the paint in an instant.

Its not the best way to do it but it can be done if you take your time.



Home made Brake Bleeding Bottle

 

I use this procedure to bleed my brakes without an assistant. My ABS was emptied when I rebuilt all my calipers, so the photos show me bleeding the low pressure side before the pump.

To bleed the calipers just pump 10psi into the reservoir and open the bleed nipple. No need to turn the ignition on.

Jaguar XJS Restoration : How to bleed Jaguar XJS teves ABS