Retrofitting Cruise Control to a 1996-1999 Jaguar XK8 4.0 V8 Email: EdmundIJones@gmail.com

Disclaimer

I’m providing this guide/write-up of my own experience, I’m happy to answer questions but I’m not

an expert and I do not accept any liabilities if you break your car following the actions or end up

having an accident.

I suggest when working under the car you take appropriate safety measures and use suitable axel

stands.

The background of my car and set-up

I do a lot of motorway miles each year in my cars and one of the main features I like to have is cruise

control. It makes long drives that bit easier. When I bought my Jaguar XK8 it was advertised as

having cruise control fitted. Sure enough, when I viewed her the buttons were on the steering wheel

but they didn’t appear to work. Upon closer examination it didn’t have the cruise control on/off

switch on the gear selector surround, just the Sport button. This didn’t put me off the purchase as it

came me the opportunity to fiddle about and try to retrofit this very useful feature. I naively

assumed somebody would have done it and there would be a “how to” guide on the internet. After

searching long and hard I found that people around the world had successfully fitted the system but

there were no write-ups. I exchanged posed with a number of people at www.jaguarforum.com who

were interested and I’d like to say a special thank you to “DevonDavid” – who was tremendous help

and very enthusiastic.

The parts you need

As I mentioned I already had the steering wheel controls but here is a full list of the parts you will

need:

Steering Wheel Buttons: LJA6480AA

Cruise Control On/Off switch for gear surround: LNC6227BB

2 button gear surround (optional): LJB6221AA

Vacuum cylinders: Don’t know.

Cruise Control Vacuum Solenoid: LJA1530AA (BB CB)

Vacuum Hoses/Pipes: Multiple pipes

Wiring Loom: Don’t know.

The easiest approach and what I used is find somebody who is braking an XK8 of the same year and

ask for the whole cruise control assembly (with pipes and wires) form a donor car. See Picture 2 for

what I received.

I got all the parts I needed of Ben at SimplyPerformance.com – I highly recommend them:

jon@simplyperformance.com

Identification and fitting the vacuum system

1 . Make sure you have a vacuum based cruise control system, you will have the Throttle Body

mounted Cruise Diaphragm Housing dome at the back centre of the engine. If you don’t have this

then you probably have a newer XK8 with an electronic cruise control system. If you have a short

hard plastic pipe then this guide is for you.

2. Make sure you have all the parts – here is what I bought from a donor car.

3. Jack up the car and remove the front drivers side wheel (UK Spec)

4. Locate the fixings holding the wheel arch liner in place and remove each one. There are 3

triangular shape nuts, 4 push to expand plastic trim fasteners and one torx screw.

Why Jaguar felt the need for three different fasteners I’m not sure.

5. Take a look inside the wheel arch – facing the rear of the car, above the tank there is a space, just

unclip the black pipe going horizontal and down so that it can be bent out of the way to aid access

into the area you need to fit the vacuum tanks in.

6. Put your arm in the wing and remove the bulb socket by twisting it a little and giving it a tug.

7. Feed the new wiring loom that came with your kit down up to the engine cavity. There is an

access hold next to the master brake cylinder – you can trace the old wire from the plug up to where

it connects next to the brake fluid reservoir.

.

8. Man handle the vacuum cylinders and all the other bits into place and affix it with a couple of nuts

you probably have in your toolbox (there are bolts already in place so I used a couple of nuts and a

socket bar extender to tighten them.

The image below shows the new wiring loom (black) that has been threaded up/down to/from the

engine bay, the old wiring loom with the indicator bulb attached and the socket from the cruise

control apparatus within nothing attached.

9. Remove the bulb from the old wiring loom and connect it to the empty socket.

10. Connect the bulb to the indicator on the car.

11. You now need to remove the old wiring loom, in the engine bay compartment on the drivers side

to the bottom right of the master brake cylinder there is a black electrical connection block, unclip

the socket/plug and pull the old wire out and thread it down to the wheel arch – you no longer need

it.

12. On this occasion I just put the loom around the back of the brake cylinder and connected the

socket/plug together. (I moved it after the photo to below the brake cylinder so that it wasn’t

straining.

13. Next up, thread the two black vacuum pipes from the vacuum solenoid/tanks through the same

hold into the engine bay – see them below after coming up.

14. Thread them under the brake cylinder and notice the small rubber bung to the bottom left, push

it out (I used a flat head screwdriver) and thread the vacuum houses through making sure to put the

rubber bung back so the pipes don’t chaff on the metal.

15. In the engine bay, take the small black pipe off the top of the throttle body vacuum diaphragm

tank to expose the male connector.

16. Unbolt the two bolts holding the plastic inlet pipe onto the top of the throttle body. This is just to

make it easier to access other pipes.

17. Down to the left of the throttle body there is a small T shape connection for two black hoses and

a terminating cap. Pull the cap off and connect up the vacuum hoses you have been threading

around, connect up the hose with the straight end (not the right angle one)

18. Finally, re-attach the plastic inlet pipe with the two bolts and make sure the seal is good, take the

other (right angled) vacuum hose you were threading around and attach it to the top of the throttle

body vacuum diaphragm tank where the little male connecter is standing up in the middle.

Inside the car

Installed the Cruise control on/off switch

Pull up the gear surround gently, I used my finder nails, under it you will find, a set of wires

connected to the Sport button and a white connector block with nothing attached poked down in

the void – this is what you connect your cruise control switch to.

Connect up the switch.

You either need to buy a new gear selector surround with the second switch hole in it or do what I

did and turn the cruise control switch on and shove it down in the hole beneath the Sport switch.

The cruise will turn on automatically when you start the car as the master switch is turned on. No

need to buy a new surround is you are budget conscious or just want to test everything works first.

Re-assemble the gear surround by snapping it back into place.

Steering wheel controls.

My steering wheel had obviously already been replaced by a previous owner so I was lucky enough

to have the controls already fitted. Either buy a new wheel with the controls in place or see this

guide to installing them: http://www.go-lpg.co.uk/XJ8_Cruise_Control.html - 2/3rds of the way

down the page.

Brake switch.

I got a new brake switch as I thought it was different but on closer inspection it wasn’t needed. The

one already fitted in my car had the required two micro switches in it. A good thing as it looks very

tricky to replace. I suggest you try out your new cruise control system before fiddling with this as you

could save a lot of time, some money a bad back and lots of sweat.

That’s it, test out your system in a nice quiet place or private road. Be careful of other people. If you

have any questions please just let me know at EdmundIJones@gmail.com