Procedure to drain, flush, and refill coolant on 240sx.
1. Move heater “Temp” control lever all the way to “Hot” position.
2. Remove undercover.
3. Open drain plug at the bottom of the radiator, and remove radiator cap.
4. Remove drain plug on cylinder block.
5. Close drain plug and tighten drain plug securely.
6. Open air relief plug (right above where the upper radiator hose attaches to the engine).
7. Fill radiator with water and close air relief plug and radiator cap.
8. Run engine and warm it up sufficiently.
9. Rev engine 2 or 3 times under no-load.
10. Stop engine and wait until it cools down.
11. Repeat step 2 through step 9 until clear water begins to drain from radiator.
12. Drain water.
13. Open radiator cap and air relief plug.
14. Fill radiator with coolant up to specified level.
15. Close air relief plug.
16. Remove reservior tank, drain coolant, then clean reservior tank.
17. Install reservior tank and fill it with coolant up to “Max” level and then install radiator cap.
18. Run engine and warm it up sufficiently.
19. Rev engine 2 or 3 times under no-load.
20. Stop engine and cool it down, then add coolant as necessary.
Quick Tip:After flushing your cooling system, make sure you fill up your cooling system completely. The KA24 engines seem to like to trap air in the system and needs to be bled completely.An easy way to bleed the system is to run the engine, and keep adding water/coolant into theradiator while shaking various parts of the car. I liked to just push down on the front bumper. Shaking the front end side to side also helped. It took about 30 minutes of this to get all of the air out.
Also:Coolant / antifreeze is used to lubricate the water pump, prevent corrosion, prevent cavitation and prevent freezing.I HIGHLY recommend using distilled water in your cooling system to prevent buildup and deposits.I also recommend using less coolant / antifreeze than typically is called for.For warm climates, I prefer 70% distilled water, 30% coolant, and a bottle of Redline Water Wetter.For colder climates, you can increase the coolant-to-water ratio, but there’s no need to exceed a 50/50 mixture.Also, changing your coolant annually will ensure you never have an overheating issue.
Lastly:I recommend changing your radiator cap annually, and replacing both radiator hoses, and your thermostat, every other year.Cheap insurance against a cooling system malfunction!