Copied this from the 370Z service manual. I included the draining, refilling, and flushing directions. DO NOT REMOVE THE DRAIN PLUGS ON CYLINDER BLOCK, thats only for when you dissemble the engine block.
You can download the service manual at this link.
2009 370z Service Manual Complete ready to Download!
ENGINE COOLANT : Draining
WARNING:
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• To avoid being scalded, never change engine coolant when the engine is hot.
• Wrap a thick cloth around radiator cap and carefully remove radiator cap. First, turn radiator cap a
quarter of a turn to release built-up pressure. Then turn radiator cap all the way.
1. Open radiator drain plug (2) at the bottom of radiator, and then remove radiator cap.

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1 : Engine under cover L A : Radiator drain plug hole
: Vehicle front
When draining all of engine coolant in the system, open water drain plugs on cylinder block. Refer
to EM-74, "Setting". O
2. Remove reservoir tank if necessary, and drain engine coolant and clean reservoir tank before installing.
3. Check drained engine coolant for contaminants such as rust, corrosion or discoloration.
If contaminated, flush the engine cooling system. Refer to MA-21, "ENGINE COOLANT : Flushing".
ENGINE COOLANT : Refilling INFOID:0000000004751765
1. Install radiator drain plug.
CAUTION:
Be sure to clean drain plug and install with new O-ring.

Revision: 2008 October MA-19 2009 370Z
MA
ENGINE MAINTENANCE
< ON-VEHICLE MAINTENANCE >
Tightening torque : Refer to CO-13, "Exploded View".
If water drain plugs on cylinder block are removed, close and tighten them. Refer to EM-113, "Dis-
assembly and Assembly".
2. Remove air cleaner case (LH). Refer to EM-27, "Exploded View".
3. Install reservoir tank if removed.
4. Check that each hose clamp has been firmly tightened.
5. Remove air relief plug (2) on radiator left side.
1 : Reservoir tank 3 : Engine cover
: Vehicle front
6. Fill radiator, and reservoir tank if removed, to specified level.
• Pour engine coolant through engine coolant filler neck slowly of less than 2 (2-1/8 US qt, 1-3/4 lmp qt) a minute
to allow air in system to escape.
• Use Genuine NISSAN Long Life Antifreeze/Coolant or
equivalent mixed with water (distilled or demineralized). Refer to MA-14, "FOR NORTH AMERICA : Fluids and Lubri- cants" (FOR NORTH AMERICA) or MA-15, "EXCEPT FOR NORTH AMERICA : Fluids and Lubricants" (EXCEPT FOR NORTH AMERICA).
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Engine coolant capacity
(With reservoir tank at “MAX” level)
: Refer to CO-25, "Periodical Maintenanc e Specification".
Reservoir tank engine coolant capacity (At “MAX” level)
A :MAX B :MIN
: Refer to CO-25,
"Periodical Maintenance Specification".
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7. When engine coolant overflows air relief hole on radiator, install air relief plug with new O-ring.
Tightening torque : Refer to CO-13, "Exploded View".
8. Repeat step 6.
9. Install air cleaner case (LH). Refer to EM-27, "Exploded View".
10. Install radiator cap.
11. Warm up engine until opening thermostat. Standard for warming-up time is approximately 10 minutes at 3,000 rpm.
• Check thermostat opening condition by touching radiator hose (lower) to see a flow of warm water.
CAUTION:
Watch water temperature gauge so as not to overheat engine.
Revision: 2008 October MA-20 2009 370Z

ENGINE MAINTENANCE
< ON-VEHICLE MAINTENANCE >
12. Stop the engine and cool down to less than approximately 50°C (122°F).
• Cool down using fan to reduce the time. A • If necessary, refill radiator up to filler neck with engine coolant.
13. Refill reservoir tank to “MAX” level line with engine coolant.
14. Repeat steps 11 through 13 two or more times with radiator cap installed until engine coolant level no B longer drops.
15. Check cooling system for leakage with engine running.
16. Warm up the engine, and check for sound of engine coolant flow while running engine from idle up to C 3,000 rpm with heater temperature controller set at several position between “COOL” and “WARM”.
• Sound may be noticeable at heater unit.
17. Repeat step 16 three times.
18. If sound is heard, bleed air from cooling system by repeating step 6, and steps from 10 to 17 until engine coolant level no longer drops.
19. Check that the reservoir tank cap is tightened.
ENGINE COOLANT : Flushing
1. Install radiator drain plug.
CAUTION:
Be sure to clean drain plug and install with new O-ring.
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Tightening torque : Refer to CO-13, "Exploded View".
If water drain plugs on cylinder block are removed, close and tighten them. Refer to EM-113, "Dis-
assembly and Assembly".
2. Remove air cleaner case (LH). Refer to EM-27, "Exploded View".
3. Install reservoir tank if removed.
4. Remove air relief plug (2) on radiator.
1 : Reservoir tank 3 : Engine cover
: Vehicle front
5. Fill radiator with water until water spills from the air relief hole, then close air relief plug.
Tightening torque : Refer to CO-13, "Exploded View".
6. Fill radiator and reservoir tank with water and reinstall radiator cap.
7. Install air cleaner case (LH). Refer to EM-27, "Exploded View".
8. Run the engine and warm it up to normal operating temperature.
9. Rev the engine two or three times under no-load.
10. Stop the engine and wait until it cools down.
11. Drain water from the system. Refer to MA-19, "ENGINE COOLANT : Draining".
12. Repeat steps 1 through 11 until clear water begins to drain from radiator.
13. Check that the reservoir tank cap is tightened.