I would say, when I bought the car, and removed the radiator it was half plugged, (probably with stop leak) and with minute rusty leaks around the fins.
My radiator guy said I was operating at 40% radiator capacity. That temp gauge would get up just past the N in stop and go traffic. Kind of nerve racking when you read all the horror stories.
I believe operating temperatures in a V-12 are a crucial thing probably even more so than your normal run about cars.
Take care of all cooling issues with a Jaguar and your half way there to reliable ownership.
My two cents.
Yes, I agree. Since most of my driving at the moment is easy on the cooling system (if it’s over 85F/29C ambient, I just don’t drive because I have no AC. Too hot!) I seem to have decent cooling. And I don’t go into the mountains.
But before I go on any long trips, and re-install my AC, I will definitely pull the radiator and have it serviced. Mine, being 33 years old, is probably not at 100% either. I was lucky when I bought the car, the coolant was nice and green, so hopefully PO’s changed it often, and never added StopLeak.
I find it interesting reading threads on here about XJ-S’s in Australia. That must be a major challenge!
You’ve got that right!
By the way, I run the 50/50 Prestone with distilled water and dump in a bottle of Hyperlube water wetter as well.
Similar here, 50/50 Zerex by Valvoline Original Green with distilled water. I’ve tried water wetter products in the past but never seem to notice a difference, so ignore. I also drain/refill radiator every 2 years, and will replace upper/lower radiator hoses every 5-ish years.
Its 93.3… however whatever you like