Coolant in the oil and coolant disappear - 4JX1 engine

Hi All,

I've 2003 4JX1 engine , the issues are that coolant disappears (can't visually identify a leak) the engine head  block is new (has less then 1000 mile) and passed all pressure tests at 6 bar and 90 cel / deg.there are residue of coolant in the oil. and once the engines starts the thick hose going out from the radiator become very hard probably due high pressure / heat.

Water pump and radiator are ok, and i prefer not to replace the engine head without understanding the failure root cause.

Appreciate  your support and advise what else should be checked since the mechanisms i approached would just replace the engine block although its new and replaced for the second time within 10k miles

Thanks

Asher