i have got a 2006 Octavia with 101200 km (62880 miles)

i have a temp problem when i drive the car and the whether temp is about 4 to 8 Celsius (40 to 80 Fahrenheit) the engine temp goes down to 70 instead of 90

after few minutes it goes again to 90 then to 70 and it keep doing that up and down between 70 - 90

it's been like that for 6 days

anyone has an advise is it a serious problem and what should i do...??

I doubt it is serious, faulty thermostat valve or engine temperature sensor might both produce that sort of problem.

Had the same thing on my last car, temp dropped when it was cold or when travelling fast on a motorway.

It is most likely the electronically controlled thermostatic valve between the engine block and the radiator. The fail mode is that they stick open (for safety I think), so the coolant is being sent round the radiator and over-cooled.

Could be wrong, but that was the culprit on my last car. However, when diagnostics are plugged in it doesn't always show anything.

I doubt it is serious, faulty thermostat valve or engine temperature sensor might both produce that sort of problem.

I'll go to the technician tomorrow as he advice the same that we need to change the thermostat .

thanks.