I changed the water pump - good results no leaks - thermostat is new - Vernet 87C and opens in boiling water test. Filled engine 1st thru thermostat opening with 50/50 -then thru reservoir tank - new hoses - installed thermostat with nipple at 12 o'clock.
Ran car after 10 minutes got OK heat with heat on full blower on low - but as temp gauge reaches 9 o'clock the top rad hose is still cold and feels empty - so thermostat not opening/air lock in engine or thermostat housing?? So massaging the top hose does nothing if thermostat closed. What is the best way to purge air out of block? Crack the housing a bit with cold engine running to bleed any air out and confirm pump circulating? Or should a head gasket be considered. I shut car down with gauge at 75% so never got near red.
No coolant loss

(I have another 240 and the top hose starts getting warm at the 9 o'clock position).

Over all car runs well when warmed up - some white smoke at start up which goes away after 10 minutes - oil cap has a tinge of white but goes away after a longer drive - I live in a humid area so possible humidity trapped in a cold block - oil is not creamy looking.

Only thing I have not changed is the rad - but could be a moot point if air in block and thermostat not opening.

BTW what is a fair head gasket replacement cost these days on a 240 - am told its relatively easy compared to todays more 'complex' cars.

Am taking it to the shop soon for a diagnostic and pressure test. Thanks for the tips.