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Will the Brake Booster Assembly from a 2004 XK8 bolt straight in to a 1990 XJS

XJS ( X27 ) 1975 - 1996 3.6 4.0 5.3 6.0

Will the Brake Booster Assembly from a 2004 XK8 bolt straight in to a 1990 XJS

 
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Old 06-22-2019, 08:06 PM
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Default Will the Brake Booster Assembly from a 2004 XK8 bolt straight in to a 1990 XJS

Hi Guys

Will the Brake Booster Assembly from a 2004 - 2006 XK8 Bolt straight into an XJS?

What I mean by assembly is the Pedal Box with just the Brake Pedal on it, does that XK8 Pedal Box have the Same Mounting Holes as the Master Cylinder Actuator on an XJS

The object of the exercise being to remove the ABS Master Cylinder Actuator and then bolt in the Non ABS Brake Booster Assembly from a 2004-2006 XK8 (ie will it bolt straight in without altering the mounting holes)

As for the plumbing I can sort that out, its just the mounting plate that I could use some advice on

I'm planning to initially keep the ABS System Stock on one of my Cars and then convert the other one to Non ABS with a Brake Booster which apart from the Plumbing will be a straight swap for the ABS Master Cylinder Actuator

So I can make a comparison on which of those two systems I like best
 
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Old 06-22-2019, 11:57 PM
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I'm waiting for an answer too! If I had nothing better to do I would pull mine out of my xk8 and try it to see! Alas I have to have one car to enjoy driving! Lol 😁 I am planning on getting some measurements tomorrow to see if the brake booster would fit under the hood on the XJS without any issues
 
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Old 06-23-2019, 01:41 AM
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OB
The XK8 has some sort of ABS system. If you are intending to do away with ABS, then install the XJS pre-ABS system, which is a straight bolt in. If you are intending to install the XK8 ABS system, then that would be a major insurance-company needing to authorise it matter.
 
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Old 06-23-2019, 02:33 AM
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Hi Timeisrelative

Having seen you were asking a similar question, I think we could probably work together on this as I've got a bit of a feeling that as the Set up on the early XK8 (2004-2006) is also made by 'Ate' who also made the ABS Master Cylinder Actuator for the XJS

That it 'Could' be a (Straight Swap Over Bolt In) but you are in a much better position to know for sure as you have both of these Cars (what year is your XK8)

As for me I have had the Master Cylinder Actuator out of my Car Countless times and so I am now going to put temptation in your way because it is only 4 Bolts and takes less than an hour to remove it

My XJS Hard Top Coup that has the Brake Booster System, has a much more positive feel when Braking and if She were a Convertible, then that's the one I'd be driving all the time!

Although I've got a 'New Black Ball' Accumulator, as the other one ruptured during the MOT and everything is working OK at the moment, when I got back to 'Orange Blossom Towers' the Brake Pump was Too Hot to touch!

And I've already had a Brake Pump burn out on one of my other Cars and unless you are an expert almost impossible to repair and while I know you may be able to get a Secondhand one, that is going to run you in the region of 100

I am really not that keen on buying one of those, when you can get a Complete XK8 Brake Booster System for the same money from a Scrap Yard, which should still be in very good condition 'The Question is will it fit?'

I'm not a big fan of ABS and while it is supposed to react faster than you can think, that theory goes out of the Window if you don't hit the Pedal quick enough!

And in case I forget to mention it over complicated when compared to the Brake Booster System in a Car like the early XK8
where as such I'm hoping that as I don't have an XK8 'You' or someone else will come up with the Answer!
 
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Old 06-23-2019, 02:40 AM
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Hi Greg

I didn't think the early XK8's had ABS

Maybe I'm wrong?
 

Last edited by orangeblossom; 06-23-2019 at 03:45 AM.
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Old 06-23-2019, 04:05 AM
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Originally Posted by orangeblossom View Post
Hi Greg

I didn't think the early XK8's had ABS

Maybe I'm wrong?
You're wrong. All Jags from 1988 have ABS. XJ40, X300, X308, X100...

And the ABS system in the X100 is a system where the brake booster is separate and the ABS block is a lump in the front left corner of the engine bay. Rather keen to failing due to bad soldering...
 
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Old 06-23-2019, 04:06 AM
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BTW., do as Greg says. Get a master cylinder and servo from a pre ABS model. That is a nearly drop in solution...
 
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Old 06-23-2019, 05:03 AM
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Alex,

Maaaaate.

The XK8 booster etc MAY be adaptable, never tried.

The XK8 has ABS, and you would need at least a donor car, in MY opinion, as modules etc etc would all be needed, and then the issue of, "will your wheel sensors actually talk to the XK8 module", DUNNO.

The Pre ABS XJS set up is the only way, again, in MY opinion.

I was involved in a conversion a very long time ago, more of a sounding board, than actual hands on. The person doing it was a basic DIY owner, and he had only one issue, and that was the pipe from teh master cylinder, under the scuttle to the LH side of the car. Not sure what his issue was, but he had a new pipe made at a brake supply company, and all was sweet. Removed the bulb from the dash component, and that was all I remember.

He had a donor 1986 car, so that was a bonus I reckon.
 
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Old 06-23-2019, 05:43 AM
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Hi Grant

Every time I look at a Photo of an XK8 Brake Booster and Brake Pedal assembly, it looks like a straight swap over Bolt in for the ABS Master Cylinder Actuator

It also looks much neater with the Low Profile Reservoir on top of the Master Cylinder as it takes up less space and being a Brake Booster, I would imagine that the Wheel Speed Sensors won't have much of a part to play anymore

If I can get one from a Scrap Yard then I would put it in to see how it goes, or should that be Stops!

Even better would be/could be, the Brake Booster from a 95 or later XJS as the ABS on that Car is a Separate unit altogether
 
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Old 06-23-2019, 08:03 AM
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That is bolt on yes and no. You will need triangle view the expansion reservoir. Hard to find. If you will install as is the reservoir will touch the bonnet. You will need some modifications of the plastic body of the booster. If you will want ABS the X300's will work.
 

Last edited by xjsv12; 06-23-2019 at 08:46 AM.
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Old 06-23-2019, 08:27 AM
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My xk8 is an early 97 built in 96. If it were just a "pull out and try" I'd do it, but only because of having to rebleed the system, which isn't really that bad, but it is my main vehicle right now. So I don't want it to be down seeing as how I have work to do on so much other stuff. I will check some measurements though
 
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Old 06-23-2019, 09:37 AM
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Ok so I got some rough measurements and I actually think it might be a possibility. The only thing I'm not sure of is the angle of the firewall. If it's a steeper angle on either one then it might not work. The mounting holes actually look pretty close, couldn't get a perfect measurement width wise, but I think it's basically the same. If anything the wheel well maybe an issue due to the length of the xk8 system. There are also only 2 lines out of the xk8 master cylinder, so I'm guessing you would at least need a proportioning valve

Overall length of system xjs

Overall length of system xk8

XJS measurement from top bolt forward

Xk8 measurement from top bolt forward

Height of XJS system

Height of xk8 system

Width of xk8 system

Width of XJS system
 
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Old 06-23-2019, 09:40 AM
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Just figured I'd post my door stickers for year and number purposes


 
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Old 06-23-2019, 10:24 AM
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Hi XJSV12

The Reservoir would be the least of my problems, as I know where I can get one

Just hoping that the Brake Booster might be a straight swap over for the Master Cylinder Actuator

Thanks for your help
 
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Old 06-23-2019, 10:26 AM
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Hi Timeisrelative

OOOOH, that does look so Temptingly like a Straight Swap

So tempted to get the Plastic out and buy one!
 
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Old 06-23-2019, 11:43 AM
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When I will at home I'll make some pics of my mods with XK8 brakes on my car
 
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Old 06-23-2019, 12:11 PM
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So you're saying the x300 brake assembly is a direct bolt in job?
 
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Old 06-23-2019, 12:36 PM
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X300's ABS hydraulic and control unit only.
I am not sure what XK8 ABS unit will work like standalone.
 
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Old 06-23-2019, 04:34 PM
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There are two type of brake X100, three holes- studs of booster and four holes. Four holes is smaller and a little more effective. Four holes type has alloy master cylinder.
I did comparison of both types. Four holes is better. Original facelift XJS vacuum brake booster has three holes fitting.
To install, you need to slightly modify the plastic case. I made the holes larger and set the washers to increase the tilt and to move down the master cylinder.

a little relocate the crossbar

ABS system.
Hydraulics and control unit from the X300 can work well. There are two systems with and without traction control. For traction control you need to do an extra tube for the rear brakes and the throttle pedal cable.
For both systems you need to move the brake pipes. The original rear speed sensors do not work normally, they are needed from the X308 or X100 with wires. Wiring is not difficult to connect, it needs three positives, one ground, diagnostics and fault lamp, extend the wires of the rear sensors.



With traction control
 
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Old 06-23-2019, 04:40 PM
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What car is the triangle reservoir from?
 
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