Full disclosure, I should have checked my liquids.
Went for a drive on the weekend, after about 60 miles whilst on the motorway, when i was accelerating i could hear a grinding noise, the more i accelerate the faster the rattling/grinding became.
Then the car lost complete power. I pulled up to the hard shoulder and the car was smoking from the front.
Opened the bonnet and plumes of smoke poured out.....a few minutes later...BANG!
Something next to the super charger (if facing the car from the front bonnet, then the right side, where the oil cap is) something popped and warm water/dirty water/kind of sweet tasting water just burst out. I know the taste cos it went all over me.
When recovery chap came and he turned the key, thick white smoke was coming out of the exhaust.
When the car was lowered off the trailer, the trailer bed had coolant and oil.
Checked it this morning and there's zero oil or coolant in the car.
Engine knackered, and perhaps gearbox, if water got into it. I'd assume that supercharged V8s meet hedges reasonably often, so there ought to be a relatively good supply of second hand engines from breakers yards, though fitting might be expensive.
(P.S. Do you really mean it's just done 150 miles )
1981 XJ6 Series III basket case
1991 XJS V12 "facelift"
2008 XJ TDVi
If your good with the spanners , £1200-1500 should sort it , then again you could pick another one up for £2000-3000 , take the better parts off the dead one , put on the new one , then sale the parts you have left , or all the car , may end up £1000 down !!