Sounds about right to me horu. Did you change the thermostat at the same time? Are you losing any water? Any smoke from the exhaust?
Clive has the 1HZ so may be able to comment on needle position but to me that sounds right.
If you have no other symptoms you may have got away with it. Monitor it and see maybe.
Horu, my HZJ 80 has always run with the temp needle at Centre or horizontal, whichever way up you view the gauge.
The centre or normal "band" is quite wide so if it deviates too much from centre, then that's the time to think something may be amiss.
As for the thermostat, they do fail occasionally, as follows:
1. They stick in the open position.
This causes the warm-up time to get longer and in extreme cold conditions, the engine may never get to running themperature. It happened to me and the worst effect in the winter was a very cool heater. A new thermostat cured it, now the engine is up to temperature in about 5 minutes from start-up, irrespective of the outside temperature.
2. They stick in the closed position.
This causes the engine to overheat. The gauge will rise from the cold position, but won't stop in the centre. It will continue to rise into the red, and if the engine isn't turned off at this stage, the coolant will boil and it will all be blown into and overflow the expansion bottle. Once dry of coolant, the engine will just get hotter until something breaks, usually the cylinder head, which either warps, cracks or both. If you're very lucky, it will just blow the cylinder head gasket, but that's rare, we're usually not that lucky.
So, if your warm-up time is acceptable and the gauge stays at centre (or thereabouts, a few mm either side is still normal) then I'd say you have no problems.
Danger is when the needle goes right to the top.
Good luck...
