Air in cooling system
If there is air in your cooling system, it will not perform as it should and temperatures will rise above what's safe.
Take off coolant bottle cap, start car and let it run. see if there are bubbles coming out. give it a couple of revs until you don't see any bubbles coming out.
Monitor the procedure with an OBD2 scanner connected with an obd app on your phone. Idle temperatures must not get near 105°C / 220F if idling.
WEak old cooling fans
Over time the performance of cooling fans deteriorates and sometimes to the point where it can't do the job it's supposed to do.
Upgrading your fans to new ones or the Mishimoto aluminium ones is an investment worth while, especially in the long run.
Click HERE for the Install video
low coolant level
Check your coolant level and make sure it reaches the middle of the bottle
If you don't see any coolant in the bottle, top it up and see if it stays there. If not, you may have a leak and need to pressure test your system to see where the leak is.
Coolant may be leaking out of the radiator, hoses or coolant bottle.
To find the leak, you must perform a pressure test.
How to video coming soon.
Over time, radiators can get clogged and almost no coolant is getting cooled.
The easiest way to test it is to do a flow test, this usually requires you to take it out.
Alternatively with the radiator still on, you can do a flush and see if coolant clears up after 1-2 flushes. If not, the radiator may be clogged.
When temperatures get hot, the thermostat opens to let cool the coolant. If the thermostat is stuck close, the coolant can not cool down and so can't the engine, resulting in very high temperatures.
You can test the thermostat by putting it in a pan full of water and heating it to 90°C. If the thermostat opens, then It's good. If not, it's stuck and you must replace it. Replacing it is like 20€ so if you went trough all the trouble of taking it out, install a new one.
old dirty contaminated coolant
With time coolant deteriorates and with all the dirt it accumulates, the cooling effect it provides becomes poor.
To solve this, flush your cooling system every 2 years.
Click HERE to see how to flush the cooling system of your Rx8.
Always use an OBD2 scanner when flushing to see actual temperatures. Don't rely on the stock gauge. Optimal working temperature 86-90°C
failing water pump
A failing water pump means coolant is not getting pushed trough the system and it can not cool down.
Usually you see a coolant leak at the front-center of your car, steam from the radiator or loose water pump pulley that make a whining noise.