The fan clutch has not been doing its job, so as the truck heats up, the radiator cap wasn't sealing all too well and resulted in coolant loss while driving.
New AISIN fan clutch and a Stant 10233 radiator cap, no more problems.
Also got the input shaft seal for the upcoming clutch job. The clutch and trans parts are ready, but the 300ZX has to be sold and the 3rd gen driving before I touch it. One step at a time!!
Needs a bit of clean up after the mess the coolant made.
All is well...