The first time I ran my current car down the road, at over 100 Km/H I started getting green coolant droplets out of the ventilation outlets.
Not needing heat in this area I simply bypassed the heater, but maintained the flow of coolant from the back of the head to the water pump. I think this is necessary for good cooling. I have noticed that the 8 has a water on off cock in the heater coolant circuit there, but the 7 doesn't. My guess is it requires constant flow from the back of the head.
Even when I fitted the air conditioning unit I left the hot water on bypass.
One thing we have often found with both the 7 & the 8 is that both can & often do get an airlock in the coolant circulation, particularly when filled from empty. As you have recently fitted new bits in the system, you may have one. Try removing the hose from the thermostat housing, & fill the system via that hose. Then reconnect it with it full of coolant. This often helps.
I have fitted the coolant reclaim system from an old Toyota Cressida, which keeps my coolant level about 2 inches higher in the header tank, & overcomes any airlock when filling.
Hasbeen