I’d like to add aftermarket Oil Pressure and Coolant Temp gauges in addition to the stock vertical gauges, just so I know EXACTLY what those readings are.
Any advice on how to hook them up in parallel to stock gauges? Can they both be electrical?
Not sure where to locate them in the car yet.
1988 XJS
I’m confused. You want greater precision in gauge readings, yet you expect to simply tee off the OEM sending units? You believe that the vertical gauges are somehow unreliable but the sending units are spot-on without question?
Fact is, the OEM vertical gauges ain’t bad. What is bad are the connections to them, starting with the flexible circuit on through the screw threads digging into the PCB holding the gauge itself and then on to the flaky grounding of the entire dash cluster. Pull the dash out, disassemble to the point where you’re holding each gauge’s guts in your hand, and put it back together making sure that every electrical connection is secure beyond question.
well, sending units are usually as close to spot-on as they can get. I have to assume so.
I am in the middle of cleaning/repairing my instrument cluster to make sure they are as reliable as can be. Amazing how much corrosion there was. Am replacing the screws into the PCB with stainless steel screws/washers.
I just like an actual F number, and an actual PSI number. A little below or above N doesn’t tell me much.
You’ll need to use the sending units that come with the new gauges, whether they are electrical or mechanical. There is an unused oil pressure port on the side of the tower where the idiot light and dash gauge sending units are. Typically a plug that has a slot like a screw is installed. There might an un-used plug on one of the water manifolds somewhere for the water temp gauge.
I would put the aux water temp gauge on the opposite bank as the dash gauge, theory being there are two t-stats and if the one not on the monitored bank sticks closed it might take awhile to realize. This way you are monitoring both banks, one from dash gauge and one from aux gauge.
Lots of options. I chose mechanical gauges (easier to get 270d sweep which I prefer) and put a water temp gauge on both banks. It’s been posted here a few times but details are at the bottom of this page:
http://goflyrc.com/projects/XJS/xjs.htm
Regards
Bob
thanks for the info! I like the idea of dual temp gauges with the oil pressure in the middle (looked at link). Might do that. Not sure if I need a 1980s electronic read out for mpg, etc 
You said there’s a spare oil pressure port on side of tower…not sure where you mean. Passenger or Driver side? Sounds like there are two water temp ports if you pull out air pump sensor and charcoal canister sensor, according to that link.
Do you off hand know what the thread diameters are of the ports? standard? or will i need adapters?
Thanks!
At the back of the V, near the firewall, is a cast “tower”. http://goflyrc.com/projects/XJS/P5190092.JPG. One oil sensor is on top, the other sticks out at about a 45d angle towards the right/passenger side. On my car, the available port was at a 45d angle towards the left/drivers side. At the back of the tower you can see the two hard lines coming in from the back of the cam blocks, just FYI.
The ports are a true mish-mash of threads. About all you can be sure of is that the gauges will have standard US threads (if you buy in US), typically 1/4 NPT or National Pipe Taper. So you’ll need a bushing with a male “Jaguar” thread on one side and female 1/4 NPT on the other. By Jaguar thread I mean that it could be npt, bsp, bspt… See Kirby’s book for a treatise.
As mentioned in the link, the right-rear water manifold where the air pump switch used to be was already 1/4 npt on my car. (Note that you need to understand how the air pump works, if you have one, before deleting this switch. It re-routes the fresh air to atmosphere after warm up. Do this wrong and your air pump will pump into the engine all the time. Separate conversation, all details in Kirby’s book.)
For the left front water manifold I removed a thermo switch that was some mystery-thread and re-tapped to 1/4 NPT.
I don’t recall what I did with oil sender… I want to say it was 1/4 BPT (British Pipe Thread) and I got a bushing from McMaster Carr. But I really don’t remember.
FWIW my trip computer was not only haunted, randomly displaying various values, it also turned out to be the source of my car-parked battery drain. With good form and proper wrist action the trip computer will remain airborne for 38-45 feet when you toss it over the wall.
Regards
Bob
ha ha, I’ll probably keep the trip computer somewhere on my desk, to marvel at 80s technology.
thanks for the info on the threads and ports. Will look for them this weekend. Your link is awesome, I will probably follow in your footsteps. Love your clean and tidy engine! I may paint my fuel rail too, looks cool. How easy was it to remove/install intake manifolds?
Where did you get your panel to fit the gauges into? Looks like it naturally matches the dash material.
Thanks Greg-
All the gold stuff is cad plated, which is what it was from the factory. Decided I liked the look well enough, cheaper than chrome. Also a fan of powder paint.
Nothing that I’ve done is really that difficult to disassemble, basic rule of thumb on this engine is you’re going to have to remove a lot of stuff to get to most things. Take good pictures. The “before” pics on my site are about 5pct of what I took during disassembly. I find the factory parts manual with the exploded drawings to be as useful as the ROM. Kirby’s book has invaluable tips on improvements and HOW and WHY things work. Panel was fabbed from 1/8 aluminum with a couple of clamp “ears” to grab the lip of the dash, then painted with black wrinkle paint.
Regards
Bob
Had to add my two cents. I welded a 1/2" pipe thread boss in the rear part of each water rail (that I replaced with SS rails). Installed Auto Meter (AM) temp sensor’s in each rail and oil pressure sender in place of the screw in the oil sensor tower. I installed the gauges in the computer/clock opening in the cabin. Auto Meter sells a three gauge pod you can mount on the top of the dash, $104… if you don’t mind drilling holes & you can live with “AUTOMETER” inscribed on the top of the pod.
Bob-
Have found the oil sender location and have an adapter from BSP to NPT.
I’m curious, did you mount the sender straight into the location, or did you use a short line so that you could mount the sender not on the engine?
Just curious if the V12 engine vibration and heat will kill the oil sender. I’m using electric.
Thanks.
Hi Greg-
A properly tuned Jaguar V12 does not vibrate. Ever. 
My gauges are mechanical, so in the case of the oil pressure gauge it’s a capillary tube, not a sending unit. Were they electric I’d put the sending unit right into the adapter. Won’t hurt it a bit and makes for a simpler install.
Regards
Bob
