To flush the cooling system, you should remove the lower radiator hose either from the
water pump or the radiator.
I found this extremely difficult to reach and gave up!
I just inserted my water hose into the top radiator hose and kept adding water until clear water came out of the thermostat hole and then let it all drain out from the radiator drain plug.
Place the thermostat into the cylinder head with the little hole facing up. This helps with bleeding the air out of the system.
Install the housing and bolt it down. These bolts do not need to be super tight, just enough to hold the thing down and not leak.
Replace the top hose onto the housing and close the radiator drain plug.
Fill the coolant reservoir with a 50/50 mix of anti-freeze and distilled water. My car took about 5
liters of coolant.
Now run the car up for 10-15 minutes and check the following:
1. The engine temperature gauge settles at the 1/2 way mark and the fans come on to cool the car down.
2. There are no leaks at the thermostat housing and the radiator hoses
3. The coolant level is stable
If everything checks out, reinstall the engine shield and call it a day!