D24 NA cooling

[bost724]

I have a few problems with the cooling system in my D24.

I replaced the thermostat with a new Borg warner 87°C thermostat and flushed the coolant out and filled in new coolant. Taking the car for a test drive, it heats up pretty well and fast but the needle stops at around 85°C, maybe 87-ish, pushing the engine a little bit makes the temp go up a bit but its still not up to 90°C. I had the heater on and there was hot air coming out so atleast thats good. I pulled over and the upper coolant hose is hot but the lower hose going from the thermostat to the radiator is cold, i dipped my finger into the expansion tank and the coolant is completely cold. I also feel like there might be air in the cooling system but i cant find any info how to correctly do a coolant change on this engine and if there's a way to get the air out of the cooling system. I have read that the D24 takes roughly 11.5 liters of coolant but I've only put around 8.5 liters in so far and the expansion tank is on max.

Should i go for a longer test drive to really get the engine running under different loads for a longer time?

Also completely unrelated to all this, i need to do an oil change. Does anyone know how much i need to tighten the drain plug on the oil pan?

Thanks for the help.