I have a Jaguar XJ8 (2004) that is running hot. Fans come on at designated time. I have replaced water pump & thermostat. Still have the same issue. Also no heat. Can someone give some guidance? Am going to try back flushing lines & heater core next.

 

Do a search on burping the trapped air. Some call it bleeding the system. I think you have a trapped air pocket.

 

Do these models have an aux coolant pump (like mine has)? If so, check it & its circuit.