I got the "Cat" back together, on the road, and looking good!
Thanks for all of your information and help.

 

My 2006 VDP gave me a scare today. Crawling along the 405 freeway today the temp guage rose to the 'H' and the red warning light came on. I turned the climate off and put the heater on full blast; temp settled down, but I noticed the rad fans were going crazy. Hopefully the few hundred yards I drove the car with the red light on won't cause a problem. Taking the car into Galpin tomorrow to get it fixed; still under warranty. Will let you know the cause once they look at it. Fingers crossed.

 

Galpin confirms that the thermostat is at fault and they are replacing it under my warranty. They tell me that small pieces of the thermostat and/or gasket come lose and can wreak havoc on the cooling system, so they are also changing the water pump, also under warranty. They also recommend replacing the serpentine belt (the car has 58k miles and the belt change is due at 70k), since they have to remove the old belt anyway it seems like a good idea.

In addition, I have had the pleasure of driving a newish XJ x351 loaner car - a 5.0 litre XJL. Very interesting. Here are my observations;

1. Fantastic sytling, inside and out. Good to stare at.
2. Use of wood and leather still there, though muted
3. Of course it has more nice electronic/iphone gizmos, missing on my 2006 XJ VDP.
4. 8 speed gearbox with paddle shifters is a lot of fun.
5. Economy still possible - managed 31mpg on a short 20 mile freeway commute going 68-70 mph.
6. My wife likes it

But I won't be buying one and here is why. I'm 6'5" and try as I might, I cannot get comfortable in the driving seat without feeling I am hemmed in and too close to the roof. What a shame. The windshield slopes far more dramatically than in my XJ VDP.

 

[QUOTE=clackkent;1093968]Galpin confirms that the thermostat is at fault and they are replacing it under my warranty. They tell me that small pieces of the thermostat and/or gasket come lose and can wreak havoc on the cooling system, so they are also changing the water pump, also under warranty.

Do you mean THERMOSTAT OR THERMOSTAT HOUSING??

I wound rather have them replace the housing than the water pump.

see the various posts further up this thread, with photos.