Good Day All,

I have an issue with my 1.8 TFSI CJEB , coolant was boiling and overflowing from the reservoir- I had suspected it was the thermostat housing + waterpump so I went ahead and replaced them with a second hand unit- however the exact same problem persists.

I went ahead and flushed the radiator, plus bled the system of any air- however this time decided to turn the heater on its lowest setting, and weirdly all the issues had gone away, no boiling coolant, no over flowing or steaming, no coolant loss, no over heating , however the only thing I've noticed is that the temp gauge now doesn't go beyond around 70 degrees, my daily commute to work is around 10km return , so I'm not sure if the issues will begin if driven longer.

Any ideas as to what the issue may be in the cooling system?