Join Date: Sep 2003
Location: Auckland New Zealand
Thanked 33 Times in 30 Posts
Rep Power: 12
Hydrolock generally speaking will only blow a head gasket between the cylinder and the water jacket and will not always maifest itself in water/oil mixing. Also this would, even if it doesn't result in serious internal damage (bent conrods, cracked pistons), always result in a noticeable misfiire because such a blown gasket will reduce compression which is essential to ignition on a diesel engine.
More likely is a serious overheat which causes a little distortion in the head/block joint and create a leak between the water jacket and an oil gallery. This will not cause any other signs of failure than the creamy oil and will not result in a misfire unless it goes to a cylinder.
The second situation is way more sinister because an oil flush/change could mask the condition (for a while) with no other symptoms evident.
Hope this helps.