Spain D40 co2 in coolant - cold engine

[Nostur]

Hi, as the title says, I have 2006 D40 2.5d, I put in new radiator, thermostat and water pump, but suddenly get overheating and I just did CO2 test and have it in coolant with cold engine.

I don't understand how is it possible, since thermostat shouldn't let coolant inside engine, thus have no idea where the CO2 is getting in the system.

Anyone has any ideas, before I start taking the engine apart to check on head gasket etc?

Btw. I have been doing it with demineralized water, to test it and save money on coolant, if I'm gonna drain it.

Thanks!

 

[YD25Frontier]

EGR cooler? common issue with many newer diesels.

 

[Bigbark]

Silly questions but did you bleed the system ? Is thermostat in backwards ?

 

[Bigbark]

Because air in system will cause over heating. Same as thermostat and jiggle valve installed incorrectly.

 

[Old.Tony]

If there's damage to the head gasket you could get CO2 in the coolant whether it's hot or cold. How's the pressure in the radiator? Excessive? Any bubbling?