I got a deal on this 2004 Kubota RTV 900, 3 cylinder diesel D902. The issue with it is it got hot and overheated. Previous owner put in a new radiator, thermostat and replaced the head gasket. He wasn’t sure how to adjust the valve lash so not sure what he done there after reinstalling the head. It starts and runs great but temp gets almost to the red on the temp gauge in a matter of 2-3 minutes. Could the valve lash be the issue or something else internal other than maybe bad water pump or faulty thermostat? Also fan never turns on even as temp gauge comes up. Lower radiator hose cool and top hose just warm in that short amount of time. Thanks for the help!