Today, i suddently found out the thermometer reading is lowest, so I check the coolant, it is all gone. I just top up last month. but last time I forgot to mix with water!! Will it cause serious problem?

So I topup the coolant with water half-half, but the thermometer reading is lowest, nothing changed, I guess if the pipe is blocked or sth? Quite worry about it.

Anyone could help me? sorry about the english...

Sounds like either broken temperature sender or problem with wiring.

You could have an air lock in your system preventing the water from circulating. An equally bad problem is though, where did all your water go, leaking radiator or matrix, failed head gasket?