Changing engine coolant

General

According to the workshop manual the operating temperature is when the radiator fans are running. This happens at 91C-95C (196F-203F).

Real life results show that in normal weather conditions the engine coolant temperature operates between 82C-90C (180F-194F).

At 78C (172F) the thermostat will start to open and will be fully opened at 90C (194F).

LHD: 6,5L / 6,87qts engine coolant fluid (or a little more if you would like to "flush" the engine)
RHD: 6,4L / 6,77qts engine coolant fluid (or a little more if you would like to "flush" the engine)
12mm wrench
Oil/Fluid catch pan
Floor jack + 2 jack stands
Kapton tape
Cable ties
Clear plastic hose (optional)

Make sure that the engine is cold. Never open the cooling system when the engine is hot.
Put the car in the first gear and set the parking brake.
Turn on the ignition and set the temperature of the A/C to maximum heat. Make sure the A/C button is off (green LED not active).
Wait 10 seconds and then turn off the ignition.
Jack up the car on the front by using the central jacking point near the engine.
There are two front-jacking-points on each side. Place one jack stand on each side at the jacking-point that is the furthest away from the front wheel.
Lower and remove your floor jack (or keep it in place for extra safety)
You want to make sure that the front of your S2000 is elevated.

The white colored engine coolant fluid draining bolt is located at the bottom left side of the radiator.
Place your oil/fluid catch pan below the engine coolant fluid drain bolt.
Remove the radiator cap on the top of the radiator. The engine has to be cold!
Slightly screw open the bleeding valve near the throttle body.
Remove the rubber cap from the bleeding port near the firewall (only applicable to LHD models).
Remove the engine coolant fluid drain bolt.
The old engine coolant fluid will now drain into the oil catch pan and you might need to re-adjust your oil catch pan.
Draining the radiator completely can take up to 2 hours.
In the meantime unscrew and remove the cap of the coolant overflow reservoir
Remove the coolant overflow reservoir by simply pulling it upwards.
Empty the reservoir and clean/flush it with water. Use tap water, not distilled water (Distilled water).
If possible: Once no more fluid is coming out of the radiator, lower the front of you car and elevate the back of your car. When no more fluid is draining out of the radiator, lower the back of your car and elevate the front again.
At this point there will still be engine coolant fluid inside your engine and some hoses.
If you want to get it out you will need to remove the thermostat. See "tbc".
Now only very little engine coolant fluid is left in your system.
If you also want to get the last bit out of your system you can use compressed air to push it out of the engine and hoses.

Once all the fluid has been drained I like to fill fresh engine coolant fluid into the radiator to "rinse or flush" it.
Wait until no engine coolant fluid (either old or new from "rinsing") comes out of the radiator.

Make sure your thermostat and all hoses are connected again.
Install the coolant overflow reservoir.
The bleeding valve on the throttle body and on the draining port on the firewall should still be opened.
Hand tighten the engine coolant fluid draining bolt on the bottom left side of the radiator.
Put a funnel inside the filling port on the top of the radiator and seal the connection of funnel/port with kapton tape.
Optional: Put a clear plastic hose on the bleeding port near the firewall as well as on the bleeding valve near the throttle body.
Slowly pour in engine coolant fluid until it starts to leak out of the bleeding port near the firewall.
Close the bleeding port with the rubber cap.
Continue to slowly pour engine coolant fluid until it starts leaking out of the bleeding valve near the throttle body.
Close the bleeding valve.
Continue filling the radiator until coolant stays in your funnel.
Pour engine coolant fluid in your funnel until it is half full.
Make sure your car is in neutral gearing.
Start the engine and let it run for 30 seconds. Turn off the engine.
Add engine coolant fluid in your funnel until it is half full.

Follow the instructions of Pre-conditions and jacking up the car
Make sure the engine is cold.
Use kapton tape and cable ties (or anything else) to block the hose inside the cap of the coolant overflow reservoir. As we bleed the system it might flow through the bypass into the coolant overflow reservoir causing it to overflow.
Place a funnel in the filling port of the radiator and seal the connection of radiator/funnel with kapton tape.
Add engine coolant fluid in your funnel until it is half full.
Make sure your car is in neutral gearing.
Start the engine and let it run until the radiator fans turn on twice while always ensuring that the funnel doesn't go empty. If required, pour engine coolant fluid into the funnel.
You should see bubbles coming out of your funnel while the engine warms up.
Turn off the engine.
Slightly open the bleeding valve near the throttle body.
You should now hear a hissing as air comes out of the system.
It can take several minutes until the hissing stops.
Make sure the funnel doesn't go empty. If required, pour engine coolant fluid into the funnel.
When the hissing stops, squeeze the thick upper radiator hose with your hands to make sure no more bubbles come out of the bleeding valve.
Once you notice a continuous leak of fluid out of the bleeding valve, keep the radiator hose squeezed while tightening the bleeding valve.
Once the bleeding valve is closed your can stop squeezing the radiator hose.
Start the engine, turn the A/C heating vent to max