Hi Guys

Since the ABS Brake Pump on my 1990 XJS V12 Burnt out, I have been considering 'Retro Fitting' a Brake Booster

I've already found an XJS Master Cylinder to go on the Vacuum Brake Booster but would it be also possible to use my Original Pedal Box from my 1990 XJS V12

The reason being that I wouldn't have to alter or improvise the Brake Switch and all I would need to buy is the Vacuum Booster

Which I could get from a 'Car Breakers' as I 'believe' its exactly the same as fitted to a 1996 to 2004 XKR or XK8




If I undid those 4 Bolts just to the left of the Pedal Box Mounting Holes, would I be able to bolt on a Vacuum Brake Booster so I would be able to keep the Original Brake Light Setup

 

Nope. The pedal box changed in order to accept the ABS activator.

 

That's a real shame Daim, back to the drawing board I guess

 

If I were you and in that situation, I'd see if I could get either the pump rebuilt or fit a Pre-ABS system and remove the sensors and gubbins.

You can get a good brake pedal and Master cylinder with booster for probably like £50. I mean, I'm selling a brake booster with master cylinder from my XJ8 which is the same as that from an XK8/XKR (they share the same parts). You can try it with that. But the brake servo/booster needs 4 equally spaced bolts. The ABS pedal mount block thing (the parts the actuator is mounted to) is like a one sided trapezoid shape...

 

Hi Daim

Cheers!

Have you got a Pic/s of the Brake Pedal and Master Cylinder, so I can see what I'm looking for

When you say Pre-ABS system, do you mean Brake Booster?

(not too well up on this sort of stuff at the moment)

 

Alex
Everything you need in these pics
Greg

 

Hi Greg

Cheers!

That Pedal Box looks a bit different, is the one from an XK8 the same?

 

The XK one is TOTALLY different. It is ALL plastic. It looks like this... The top riight is where most of it is. It would NEVER fit in the XJ-S engine bay... Not without hacking around in the metal work...



As I wrote above, go the XJ-S pre ABS system i.e. with the normal booster version unit. The XJ and XK ABS systems run TOTALLY different. The master cylinder only has TWO connections. The rest is sorted in the ABS hydraulic block with integrated pump.

 

Hi Daim

I don't quite understand what you mean

If you go for the Brake Booster System without ABS

Why do you say the rest is sorted in the ABS Hydraulic block with integrated pump

Surely if you have the Non ABS Booster System then you wouldn't have the ABS hydraulic block with integrated pump?

 

I wasn't sure if you wanted to fit a later ABS system instead. If you get the brake system from an earlier car without ABS, then there is no requirement for an ABS pump.

 

OB
Daim means fit the earlier non-ABS system, as my and Grants car have OEM

 

Hi Greg@Daim

Cheers! I've got it now but

One more question: Would you undo the Pedal Box (with the Brake Booster on it) from under the Bonnet or from inside the Car under the Dash

Where you would presumably have to stand on your head, as it does sound a bit of a nightmare to take one of these out

Unlike the ABS Pedal Box which can all be done from under the Bonnet in less than 30 minutes

 

The pedal box is bolted down by four nuts on studs set into the bodywork, you undo the nuts from the engine bay, using various spanners as two of them are a bit inaccessible - but you knew that without being told!

 

Hi Greg

While I know that the ABS Master Cylinder Actuator is held in by 4 Bolts that just screw in

What I wasn't sure about was how the Brake Booster is fixed into a donor Car and didn't know if it was the same fixing or whether you had to undo 4 Nuts underneath the Dashboard

 

OB
Are you talking about an XJS with the pre-ABS system? If so,the brake vacuum servo is bolted to the brake pedal casting by four studs and nuts (all clearly visible in my pics above) and the brake pedal casting itself is fixed onto studs on the bodywork by four nuts (one of which you can clearly see in the final pic above, just below the fluid reservoir). You undo the four nuts that hold the casting and the entire thing lifts out upwards, casting pedal and all.
If you are asking how the brake system is fixed in some other Jaguar model, I have no idea.

 

Both systems, booster and ABS, are connected the same way to the car. Even the same mounting points are used.

 

Hi Daim@Greg

Yup that's what I needed to know, I get that the Fixing Holes are the same but wondered if the earlier Cars

Used the 4 Stud Fixing that you can undo from under the Bonnet or used 4 Nuts and Bolts instead of 4 Studs

Which would make removing it more difficult, in the event that those nuts and bolts had gone rusty