Jaguar XJ40 SLS and Hydraulic brakes

Hello, I have started playing with my brothers 1988 Daimler. I have read how to get rid of the SLS (done!) and replace the brake hydraulics with a booster (done!). However, I am trying to sort out the error lights…I have read what to do for each removed system but not both… It seems that both assume the valve body stays in place. I would prefer to get rid of the entire system.

So, having looked the wiring for this system, it seems it is fairly self contained. It has battery power on an NU wire from fuse 5 in the left side fuse box, Ignition switched power from fuse 3 in the centre fuse box on a WS wire, a few earths (signal and power) and a single wire to the instrument pack, a YR wire… So I assume that this is the ONLY wire that triggers an error in the dash, and if I earth it, all should be well? or maybe power it? (Don’t think so!) or leave it open? But it looks like the valve body shorts it out to flag an error from the Low pressure and/ or low charge switches (not sure how this bit works at all) in the valve body. I don’t want to guess since I expect the instrument pack to be electrically sensitive.

Appreciate advice on this please.

I did the same on my 89 Vanden Plas. Removed all of the hydraulic components. There are a couple of error messages (Low Hydraulic Pressure, Low Hydraulic Fluid, etc.)
Once all of the components are removed from the front right side of the engine compartment (US Spec),
you are left with 3 cylindrical electrical plugs (Yellow, Black and Green).
Black male plug - has 2 wires (Black/Pink, Yellow/Brown) Connect these with a jumper wire.
Green male plug - has 4 wires (2-Black/Pink, Yellow/Red, Yellow/Black) Connect a jumper wire from the Black/Pink to the Yellow/Red next to it on the plug. Connect the other Black/Pink to the Yellow/Black next to it on the plug.
Yellow female Plug - Fill holes with silicone to protect against corrosion
This should remedy the fault codes, I believe that is everything

Thanks Martin… you have a US spec car in the UK??


no, I am in Washington DC. I also have an original 79 XJ-S with under 10,000 miles from new. After living in the UK and working on. countless Jags, it was amazing to find a completely unmolested example that sat in a garage for over 40 years

Hi, I live in Spain and need to do what you did on the SLS. Do you have a list of what you did and in what order? I plan to do this soon and any advice would be appreciated thanks.

No sorry. I dont have a parts list per se…

I used the suspension set up from a non SLS car, a brake booster for an S2 XJ6, made my own mount for the booster, and my own cover for the oil pump. From memory, thats all the parts involved… Oh, I used an aftermarket threaded boos for vacuum and a length of vacuum hose…a few hose clamps for the vacuum hose… thats it I think

Hi again, I have a quick question. I am changing the master cylinder to a vacuum system and I want to remove the pump at the front of the engine but it looks like it’s connected to the A/C system is that correct? Also can I just blank off the two extra hydraulic brake lines that assisted the brake pedal as I have removed the original master cylinder piston ram or do they have to be joined together? Thanks in advance

Just remove the 2 extra brake lines altogether.
You can remove the pump at the front of the engine (Nothing to do with the AC).
It is easy to fabricate a blanking plate to seal the hole.
Then remove the reservoir and it will clean up the engine bay.