The 300ZX convertible has been sitting pretty much untouched since 1993 - and that includes the coolant. With 32 years of factory fill in the system, I figured it was time to flush it out and start fresh.
I grabbed some Prestone cooling system cleaner, a few jugs of distilled water, and some concentrated antifreeze. The plan was to drain what I could from the radiator, flush with the cleaner, rinse with distilled water until it ran clear, and refill.
With the car up on the lift, I pulled the radiator drain and let the old coolant flow. I left the block drain plugs alone - they're nearly impossible to reach on the VG30, and I wasn't about to risk snapping a 32-year-old plug. Turns out I didn't need to worry anyway - for being 32 years old, the fluid actually still looked pretty decent. No visible corrosion, no gunk, no discoloration beyond the usual green. Nissan knew what they were doing with the factory fill on these.
After the flush and several rinse cycles with distilled water, I ended up draining about five gallons of old coolant and rinse water combined.
For the refill, I calculated the amount of concentrated antifreeze I needed by taking the total coolant capacity from the FSM and subtracting what I drained on the last flush. That gave me the volume still trapped in the block and heater core, so I could mix accordingly and hit the right ratio. Topped off the overflow reservoir and the system took the new coolant without any drama.
One more factory original fluid crossed off the list!
