Hi Guys

For those of you who may have been following the problems I have been having with the burned out Brake Pump on my 1990 XJS V12

Here is a link to the page: https://www.jaguarforums.com/forum/x...122634/page86/

That was on my 'Cherry Blossom' restoration thread, one of these burned out Brake Pumps was on my very late 1990 pre-facelift XJS V12 'The Ice Princess'

While the other burned out Brake Pump came from my 1988 XJS V12 Parts Car that also had Brake problems and was a Car that I bought from an Auction

Where my total lack of knowledge of all things XJS somehow conspired to lead me to buying this 'Lemon' that I would have been better to stay away from

Both of these burned out Brake Pumps are beyond economic repair and well out of my 'skill set' to even try and fix them

Where as such it may be better and make a lot more sense at least for me, to try and find a working secondhand one

Although I may be able to Salvage and re-use, the 'Black Ball' Accumulators that I have still fitted to Both of them

The one that was on 'The Ice Princess' is probably the best one of the two although the one from my Parts Car, may be just as good (as in probably not!)

There is a possibility, that the one on 'Cherry Blossom' may need replacing at some time as it takes quite a lot longer to pump the brake pressure up

So having a Spare Accumulator to put on if I need to, could come in very handy

But as I've never ever swapped out one of these before, I certainly could do with some advice

What is in the 'Black Ball' ? Is it full of Brake Fluid under Pressure or just full of some sort of Gas ?

Is it like a Gas Cannister, that you might have on something like a Blow Lamp or Camping Stove

Where when it's fitted on the Brake Pump from NEW the seal inside gets punctured so that it cannot be reused a second time ?

Or can be taken off and reused on another Brake Pump without losing any of its pressure

What is the best way to do this, as the one thing I want to really avoid is unscrewing the 'Black Ball' Accumulator on my Car 'Cherry Blossom'

And having the Black Ball flying off like a 'Cannon Ball' into the Bonnet/Hood, as there is a Warning on it, which tells you Not to unscrew it

 

I've done this on a Range rover with the same system. The ball can basically be unscrewed and swapped. They contain pressurised gas behind a diaphragm - when you hear the pump running it is pumping fluid into the canister, where it acts against the diaphragm meaning that there is pressure in the system available as soon as the pedal is pushed.

Because of the pressure it is vital that the system is depressurised - if you have it off the car, then you're fine as there is no pressure in the system, but if the abs accumulator and pump are installed on the car and attached to the braking system, you need to depressurise it by pressing the brake pedal a number of times, with the ignition off, of course! On a Range Rover they suggest 30 pumps of the pedal.

Then the ball unscrews. I think I had to use a chain wrench, because it's pretty tight!

 

Alex, consider the ball as a gas filled unit, just like the ***** on Citroen's hydropneumatic suspension.

The pump will push fluid into the ball. A membrane between the gas and the brake fluid separates them from each other. A sensor will notice how much pressure is in the system. So no pressure, the pump chime in. The ball hold the pressure until it drops again.

Most common fault is a leak due to a raptured membrane. When you remove the ball, make sure the system is TOTALLY depressurized. If it (the pump and ball) is removed, there will be no pressure. So you can remove the ball.

They are getting really hard to get now. Time has moved on... I remember somewheRe reading of a company being able to refurbished those pressuRe reservoires.

 

Hi Bladerunner@Daim

Many Thanks for you help guys

There is a noticeable difference in how long the Brake Pump takes to build up pressure in the Brake Pump of 50 Shades, my Grey XJS (20 Seconds)

While the Brake Pump on 'Cherry Blossom' takes (45 Seconds) and although they both have the same components in their Braking Systems

The Brake Pedal on my Grey XJS feels so much more positive and so I think that 'Cherry Blossom' may soon need a new 'Black Ball' Accumulator

As they are apparently quite hard to unscrew, do you think it would be better to take the Brake Pump out of the Car, while I swap the Ball over

 

Keeping it in the car will possibly damage the rubber mounts (overstretched/overcompressed). I'd remove the pump. It isn't a hard job, as you know yourself.

I didn't find it hard to remove mine. It was tight but not overtight. A normal 1/2" ratchet with an hex-head and done.

 

The test for the accumulator is to wait for the pump to stop running, then to press and release the brakes to see how many times you can press them before the pump kicks back in. From memory, three is ok and fewer than three means the accumulator needs replacing (do check that number!).
At least you can do a comparison across the two cars.

Personally I don't think that's the difference between the cars, unless cherryblossom really isn't holding any pressure.

 

Hi Bladerunner@Daim

Many Thanks for that useful info

On my Grey XJS the Brakes feel absolutely on point where as such I cannot remember the Pump ever 'kicking in'

But on 'Cherry Blossom' its a different story even though this Car has done only 26,000 Miles from New, the Brake Pump does cut in at times and there is also slightly more travel on the Pedal

Which maybe I can only notice as I can make a Comparison, which is leading me to think that it could be the Ball

As Both Cars have got New Calipers as well as New Brake Pads

Having put the Car away before I read this Post, I haven't yet managed to do the 'Pedal Count Test' but will report back when I do

And so I won't be swapping the ***** around just yet but if or when I do, are you supposed to put an Allen Key in the end of it or use something else?

Also I will not forget to de-pressurize the system, although I'll be taking it out of the Car so as not to strain the Mountings, so that pressure problem won't arise

Thanks once again for your help

 

Alan key. But get yourself a socket with the right bit in it.

 

There's an ebay seller who had an exact brand-new replacement for the ball on my 1994 XJS:

https://www.ebay.com/itm/NEW-BRAKE-A...72.m2749.l2649

I'd previously done what a lot of us had: scoured the web and found the usual potential sources for GM-branded replacements, etc. And there are other ebayers with units that apparently work but they're too long for the XJS, interfering with the cowl struts. But the unit referenced above fit exactly, just cleared the strut, and was a piece of cake to install. At $280 bucks, it ain't cheap, but I didn't have options. You do lose the factory yellow label; these are black with no labeling. Mine works great though. I had the dreaded on-off-on-off relay clicking with my old ball, and that was instantly cured. I've not timed my pump-up pressure from full stop but it feels like maybe :15 seconds, tops.
Good luck!

 

Whoops! Messed up the ebay link. It's here:

https://www.ebay.com/itm/25353661735...m=253536617351

 

Is this it OB?

https://www.jaguarclassicparts.com/uk/part/JLM1461

 

Hi Steve

Cheers that's it!

Not exactly inexpensive but you only get what you pay for and it is the Genuine Part

 

Hi Cheers!

15 Seconds is good and the same as my Grey XJS

 

I think there is a danger of following the wrong path here. If Cherryblossom is taking considerably longer to come up tp pressure, that is far more indicative of a weak pump than a problematic accumulator - think about blowing up a tyre with a hand pump against an air compressor. The tyre is the reservoir/accumulator.

 

Hi Bladerunner

I think you could be right!

But why does the Brake Pump on later model Facelift Cars not have the 'Black Ball' Accumulator like on the Pre-Facelift Cars

 

Do they not? My 1992 facelift has one. If the later cars don't have one, they must just have a different abs system.

 

 

Later XJS adopted the more modern ABS from the XJ40 or better for the XJ40 when Jaguar was getting it updated. It is a newer system without the ball. Basically a system where the pump only runs when the ABS kicks in. Otherwies you'Re always just using manual unpressurized fluid.

 

Out of interest a new ball was listed on eBay last night at £150.

 

Cheers brinny, I will check that out