yup, my yd25 was making a humming whining noise that went once it warmed up...
I had a warped manifold and a busted turbo gasket.
$88 for the manifold to be machined and about $90 for new genuine gaskets.
This hapend after a 4x4 trip where my engine over heated due to a blocked radiator. Also common to happen when going through deep water. Hot engine + cold water = not good...