Hi ,my mate has a problem with the temp on his xj6 what's happening is the temp on the dash is reading very high,but it's running ok,could it be a sensor fail ire,any ideas anyone

 

Could be air in the heater core and or hoses. He should try and get the air pockets out of the cooling. However, there's a special way to do this so you don't create more air pockets.
1. Make sure car is cool and been off for a while. Open radiator cap and put a funnel in the opening.
2. Fill the funnel about halfway with coolant.
3. Turn car on, with heat on high, but fan off!
4. You'll soon see bubbles coming up from the funnel. That's the trapped air escaping. It can take a good 30 minutes, but this could be his issue...

 

John,

Depends on which of the six different models of XJ6 he has from the original Series 1 of 1968 through to the X350 of 2003.

Graham