The thermostat is faulty. It is stuck at half-open and not regulating the water temperature. New thermostat plus gasket,diy job at £18. Buy from a local motor shop rather than from daihatsu - take the old thermostat to the shop and get it matched to ensure you get the correct type. Make certain you get the correct type of thermostat since an incorrect thermostat will not work. The daihatsu thermostat is elongated and has a 'toggel' [hole with a loose pin in the thermostat's disc] which MUST be fitted at the highest point in the housing. This stops air locks forming when filling the coolant.
DIY job takes about 1hour max. Take care not to over-tighten the housing bolts. I recollect they are 5lb/ft ... I suggest you get the correct torque setting from a CD repair manual. I have one and its invaluable - message me if you're interested in having a copy!
Thermostat
The thermostat is faulty. It is stuck at half-open and not regulating the water temperature. New thermostat plus gasket,diy job at £18. Buy from a local motor shop rather than from daihatsu - take the old thermostat to the shop and get it matched to ensure you get the correct type. Make certain you get the correct type of thermostat since an incorrect thermostat will not work. The daihatsu thermostat is elongated and has a 'toggel' [hole with a loose pin in the thermostat's disc] which MUST be fitted at the highest point in the housing. This stops air locks forming when filling the coolant.
DIY job takes about 1hour max. Take care not to over-tighten the housing bolts. I recollect they are 5lb/ft ... I suggest you get the correct torque setting from a CD repair manual. I have one and its invaluable - message me if you're interested in having a copy!