Changing engine coolant

General

Engine coolant fluid change intervals

The owners and service manual recommends the following intervals:

• Normal driving conditions: Every 96.000km / 60.000miles or 5 years (which ever comes first)

Recommended engine coolant fluid

See: Engine coolant fluid recommendations

Normal operating temperatures

According to the workshop manual the operating temperature is when the radiator fans are running. The "fan on" value is 91C-95C (196F-203F) according to the workshop manual.

How ever, real life tests have shown that in normal weather conditions the engine coolant temperature operates between 84C-90C (180F-194F) while the "fan on" value seems to be at 95C-97C (203F-207F).

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

Required tools and fluids

• 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)

How to change the engine coolant fluid

Pre-conditions and jacking up the car

• 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.

Draining the engine coolant fluid

• 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: How to change the thermostat
• 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.

Adding new engine coolant fluid

• 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.
• You should now continue with bleeding the system. Otherwise you can fill up the coolant overflow reservoir.

Bleeding the engine coolant system

• Follow the instructions of Pre-conditions and jacking up the car
• Make sure that coolant overflow reservoir is empty.
• Use kapton tape and cable ties (or anything else) to block the hose inside the cap of the coolant overflow reservoir. Otherwise as we bleed the system, coolant will flow through the bypass hose 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 and make sure it doesn't leak through the kapton tape.
• Make sure your car is in neutral gearing.
• Start the engine and let it warm up until the radiator fans turn on while always ensuring that the funnel doesn't go empty. If required, pour engine coolant fluid into the funnel. You can speed up the warm up by holding the throttle at ~2500rpm.
• You should see bubbles coming out of your funnel while the engine warms up.
• Turn off the engine after the radiator fans are off again.
• 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 fan speed to max and select the front facing fan direction.
• A/C should be off (green LED not active) and temperature should already be set to maximum heat.
• Wait until the radiator fans turn on/off twice. You can speed up this process by holding the throttle at 2500rpm. Make sure your funnel doesn't run empty and add engine coolant fluid if required.
• You should now be able to notice that the air coming out of your A/C is getting hotter.
• Turn off the engine after the radiator fans have gone on/off twice.
• Add this point there might be still bubbles coming out of your funnel and the bleeding valve near the throttle body might still hiss when opened.
• Continue the process of turning the engine on until the radiator fans turn on, then turning the engine off, followed by bleeding the system via the bleeding valve.
• You are finished as soon as (1) no more bubbles come out of your funnel, (2) the A/C vents are blowing burning hot air, (3) the bleeding valve doesn't hiss anymore when opened but instead leaks a steady flow of engine coolant fluid.

• Typically you need to bleed via the bleeding valve at least 2-3 times.
• Additionally you should let the engine run at least 30 minutes in total to push out all the bubbles via your funnel.

• Once you bled all the air out of your system there should be still engine coolant fluid inside your funnel.
• Remove the kapton tape that blocks the hose inside the cap of your coolant overflow reservoir.
• Once your remove it, the coolant fluid inside your funnel will flow through the radiators bypass out of the hose.
• Quickly put the hose/cap onto the coolant overflow reservoir.
• Remove the funnel when empty.
• Fill up the coolant overflow reservoir to "max".
• While the engine is going to cool off it will drain engine coolant fluid out of the coolant overflow reservoir.
• It is a good idea to check the level of the coolant overflow reservoir after a few hours to make sure it does not go empty.
• An empty coolant overflow reservoir might push air into your coolant system.