I burp the XKR by removing the coolant cap and running the engine until the fans come on, watching for bubbling in the header tank. Keep filling it with coolant so that the level stays near the top. If the bubbles never stop, you have a blown head gasket. This assumes that the thermostat is functioning.

The symptom of an air blockage is a very quick overheat.

 

message to the original poster, just revisited this thread and was thinking whether you simply have a leak. once you leak out a past a certain point, the temperature will start to rise followed by a near overheat. when was the last time all hoses were replaced or the radiator?

 

thank all of you for offering great advice, or not...but trying which i appreciate, you are a great bunch of car nuts....
alas....so...i am going to park it
level coolant in expansion tank
starts right up
unique color (burgundy) and only 46,000 miles
smooth idle
no while smoke
smooth at 4000 rpm
power is spot on
no oil in water or water in oil
no smell of burning coolant
no loss of power until it goes into limp home...and no message center anything anytime(it works)

warms up fine, heater and a/c excellent
fans come on at right time and turn off soon after turning it off when hot


drive it 5 miles then random immediate overheating and then maybe a min later or less the gauge can go back to normal or not

resents within minutes

park and lock it till weather gets better, folks want a convertible when that happens...i have a tender and can drive it short distances

oh i did not try a reset, cause that messes up the smog memory for months and i will have to smog it again soon, been there

battery great
car passed smog sept

go figure???

 

Sorry that an obvious solution is not presenting itself. Wish you lived closer... I thoroughly enjoy challenges like this in my garage.