Question about T27 Avensis 1.8i thermostat/engine heat issue

[JiiN 15]

Here in Finland we have winter now, so cold weathers became. I drove with my T27 1.8i Avensis couple days ago when air temperature dropped to -20 Celsius (-4 Fahrenheit).

I noticed engine heat cauge didnt rise to normal in 20 kilometeres (12,5 miles) trip with 80km/h (50mph) speed with proper pre-heat before driving. I used bluetooth OBD plug to check temperature with Torque app, and it told the coolant temperature was only about 66 Celsius (150 Fahrenheit). My previous car was E12 1.6i Corolla and it made normal temperature in same trip, no matter how cold it was outside.

Does these cars have issues with engine thermostat? Or is these cars just made to drive only in summer-time?

[TonyHSD 790]

This maybe a normal to happen when it’s so cold outside and you are driving at speeds over 20mph the wind is cooling down the engine block. To test weather the thermostat is faulty you can rise the rpm while standing and let the car reach normal operating temperature, then start driving and drive outside town at higher speeds and if temperature gauge drops dramatically then thermostat been stuck open and let engine coolant circulate through radiator and gets blown by freezing air. Also you can touch cooling system hoses to check which ones are hot and cold👍 

[Konrad C 958]

Here in the UK, especially where I live in Greater London, it rare for the temperature to go low as -5°c or -10°c, let alone -20°c. Adding to Tony's reply, what about covering the grill, so less cold air is hitting the radiator. I have yet to drive my car is extreme cold conditions. Only last summer, I replaced my water pump and mixed Toyota concentrated  red coolant with de-ionised water at 50% ratio. Today the temperature was 2°C and the car took a little longer to warm up, but the cabin got comfortable quickly. Overall the valvematic engine has not had any issues with the thermostat.

[JiiN 15]

I'll test probably tomorrow Tony's advice. It was few days little warmer weather and now it looks like it is getting colder again (-20c right now).

I havent need cover the grill in any my previous petrol cars if the thermostat is working properly (last one was E12 1.6i Corolla). I thought it is only diesel cars problem 😄

[TonyHSD 790]

When cold outside the air stream hits not only the radiators but goes through them and air cooling the engine block, another reason why engines get warmer slower, however if thermostat works as normal will stay closed and the coolant will only circulate via the car heater’s core to heat up the cabin. If the thermostat stays open in cold weather (faulty) the coolant will circulate through the radiator and will be cooled down by this ice cold air, if you drive at higher speeds and engine is under constant load with faulty thermostat the coolant temperature will drop and you will see the change on the dashboard, if you are driving downhill engine it’s not loaded, then it’s normal temperature to drop because of the cold stream that hits the engine block. Here is the reason why Toyota has introduced active grill with 2016 onwards Prius and other hybrids, grill closes automatically to keep engine  warm when needed. 👍My Auris hybrid very often in the cold weather when driving in town on ev mode cools down and temperature drops (old model no active grill) then when back on the motorway and load the car thermostat seems to work fine as the engine gets warm back again. 👍

[JiiN 15]

So i did those methods to test thermostat. It looks like the thermostat is OK. Temperature rises up (normal) and stays there if speed goes little higher and engine gets more load. Maybe these "newer" cars are made so economical (low fuel consumption, low emission, etc), so these doesn't just warm so easily like those older cars.