1988 240 230F L2.2 - Overheating Issues

[cascadia]

Hello Group. I need some advice tracking down an overheating issue. I had a slow coolant leak at the thermostat housing and at the top of the water pump. It had been leaking for some time, performance was fine and I kept the coolant topped up until I could get to it. That time was yesterday.

I replaced the thermostat (88'C) and thermo housing. Previous housing looked like it had been dropped, hence the leak. Re seated the water pump and refilled with coolant (zerex G-05) as described by the bentley manual. No more leaks!

I started the car with the coolant reservoir cap off and let it idle. Upper and lower radiator hoses got hot. No heat in the cabin and temp gauge crept up to the red. I thought perhaps I had an air bubble, so elevated the font end and let it sit overnight.

Checked this morning. The coolant level had dropped in the expansion tank. Started the car and let idle. Upper and lower radiator hoses remained cool to the touch. Heater was blowing hot air inside. Temp gauge again crept up towards the red.

Water pump is about three years old (less than 50K on it) and it seemed ok when I pulled it off to re seat. Coolant temp gauge sensor has recently been replaced and gauge bypass was installed years ago.

Any thoughts on how to proceed?
Anyone have an elegant solution to draining the coolant without dumping it everywhere out of the lower hose?