Rickg,

No need to check you thermostat. Its normal for the engine to heat up going up a hill because its burning more fuel. Its the same as if you ran up a hill you would get a lot warmer than running on the level. After 80C your thermostat is wide open and not affecting the engine temperature.

Now if it were to heat up in normal driving or when idleing, you might have as thermostat that is opening at a temperature too high, but if it normally runs about 80C, you have no problem. So if it ain't broke, don't fix it.

Notice where the red mark is on your temp gage. Its safe to run up to this temperature in hot weather and up hill with no damage to the engine as long as it full of coolant and doesn't boil. As soon as you top the hill and start downhill, your engine should cool to about 80C.

P E H