Land Rover Repair: sender wrong; temp ok but what causes running on?, fuel octane rating, radiator cap

Question
ok the sender i put in was intermotor 52770 now this is a discovery sender and they are differnt. lots of people on the web on forums who chased down bogus temp problems. I ran the engine up to the start of the red with the radiator cap off and stuck a thermometer in read only 80 degrees c so its not running hot. so i guess now my question is what causes running on. given iv'e just had the head off inside is nice and clean so it shouldn't be carbon deposits.  

Answer
Running on is caused by:

0) fuel octane rating is too low
1) excessive engine temperature
2) excessive compression ratio (planing the head too much in a valve job)
3) too much timing advance
4) idle speed too high
5) tight valves or damaged spark plug causing a hot spot
6) spark plugs whose heat range is too high

Good luck

If you find our advice useful please give us a good rating on the feedback page.

John