I was having a concern that the car would not come up to the proper temp. Thought that there was no thermostat or that it was stuck open. I thought that I would have a problem bleeding the system but there was no problem at all. I removed the lower radiator hose to drain it. Turns out that it had a thermostat (made in England). I replaced it with one made in Germany. When I got the old one out I tested it in boiling water and it seemed to work but since I bought a new one I put it in. I drained about 2 gallons out and put about 2 gallons back in. (No way could I find the block drain. I think the whole thing holds a little over 3 gal.) Drove the car a bit and the low coolant light came on so I topped it up with a little over a quart and everything is fine now. The temp gauge is right in the middle where it belongs when up to temp. I'm glad it went well.

 

No lights is a good thing!
I have read elsewhere that the thermostat gauge on our dash is not the most accurate. The difference between just below to just above the N is minimal. Mine tends to move within that range.
Does your new thermostat now move quickly to the n and stay there?

A chevy or ford will move to the mid-range mark and stay there as if its glued in place.

 

Yes, It moves to the N after a few miles and moves up and down very slightly.

 

Circa 1995 is when Jaguar threw in the towel started going to the 'dummy gauges'. My 1995 XJR had both a dummy oil pressure gauge and dummy coolant temp gauge.

The oil gauge would read dead center, and remain there constantly, at anything over about 5 psi

The coolant temp gauge was designed to read dead center over a wide range of temperatures. At xxx-point the needle would rise up to the "hot" end of the scale. On my car, for example, anything from 170ºF to 210ºF gave the exact same reading on the gauge...dead center. I never got over 210º so I can't tell you what happens after that

Not sure if the XJS was subject to the dummy gauges when built but many of the replacement sending units are the 'dummy' type....sometimes unbeknownst to the buyer

Cheers
DD

 

Mine is April 1994 and the gauges (both oil and temp) do move.
Oil is quite sensitive to temperature and to revs and covers a large psi range.
Temp also, rarely on N, though it stays in the mid range when driving normally.

 

Only the fuel pressure gauge went full retard on the XJS. I don't believe any of the other gauges did. The coolant temp still actively moves, reflecting the changing temps.