Kia Troubleshooting Questions? Ask a Mechanic
if the motor is full of sludge a new motor is the easiest. You can try running the motor with half oil half dextron atf for a few days it will clean a lot of the sludge out of the motor.. But usually sludge means oil starvation issues..
it would need to be torn down and the failure found.. all parts would need to be hot tanked.. so it would be a rebuild you could pull the valve cover and see if the failure appears to be in the head, But at that point with a sludge motor we would first attempt to flush the sludge out.. The upper end is likely starving for oil
we charge 90 dollars a hour and on a sludge motor we would write the estimate for replacement.. Its a liability thing last one to touch it usually gets the blame... and if its full of sludge and carbon its a unmaintained motor..