Coolant decreasing in the coolant tank

[Tausif]

I have a land cruiser 8 cylinder 2013 model. Lately the coolant water level goes down almost every 2 to 3 days . Mechanics have seen it and cannot find any leakage . one mechanic diagnosed head gasket leaking which we replaced it with original Toyota parts . See attached . However after replacing the gasket the problem is still there . Can anyone please suggest what may be the other causes . I have changed the radiator cap with Toyota original cap as well

 

[Beastrider]

Hello - I don’t know your specific engine but, in general, there are only a few places coolant can go: leakage outside the engine, leakage to other fluids, or out the exhaust.

Your mechanic has ruled out external leaks.

It could mix with engine oil but that would be obvious by inspecting the oil.
I have an auto 95 series where the auto transmission fluid flows through the radiator and can potentially mix - I don’t know if you have the same system.

That leaves the exhaust. If both head gaskets have been replaced and the block and head surfaces were good, then there must be a connection between the coolant and a cylinder somewhere else, not on the gasket surfaces.
Did they do a compression test and emissions test?

Lastly - you said ‘coolant water’. Does the car have water in the system or is it proper coolant (probably bright pink or red)?

 

[MisterCruiser]

I don't know this engine either but do these have an over flow expansion bottle and a rad? What's dropping, the bottle or the rad?

 

[Michael80]

Hi,
You could be loosing your coolant if it has an EGR cooler? This may be leaking and evaporated off. you really need to pressure test the coolant system.

Cheers
Michael