use a very sharp chisel to mark the screw head with a slot, use some heat and some oil - leave it alone for 10 minutes, set the engine on wooden box...
I usually removed the t stat valve to acid clean the system and then used air pressure to remove all remaining water flush in it. Install T stat back...
check the two thick vacuum pipes at the back of the manifold for leaks - they are for A/C idle up and power steering load idle up. If they leak your...
I have driven these cars quite a lot and the only time the temperature rose even without the T stat was when the radiator was blocked or the coolant...
yes - the old big fan of the W126/early W124 is very good. You can also choose an italian Spal branded fan if you are having trouble placing the fan...
the temp needle should be somewhat at half sweep - this is the 85-98 C position. which is where you should always see it, If you drive with the temp...