[Roadsters] filling up a '70 1600 cooling system

[Graeme]

  Hi Roel,
What you need is a thermostat with a jiggle valve.
This is a little weighted dooby that normally closes off a tiny hole in the
thermostat plate.
When you fill up the cooling system, the valve is pushed open by the
escaping air.
When the coolant reaches the thermostat, the valve is closed off.
A tiny hole in the thermo plate will achieve the same thing.
Just big enough to bleed the trapped air but not pass a huge amount of water
[as it were!]

The cap on the radiator is not a pressure cap, just a sealing cap.
The pressure cap should be on the overflow tank which gets the burped air
from the system.

I have a pic. Of the thermo. With jiggler if you want one.

Every time I drain the cooling system I have the most incredibly difficult
time filling it back up.  Because the thermostat's closed, it's virtually
impossible to get the block filled with water.  The very suboptimal solution
I've come up with is to run the engine half dry until the thermostat opens
despite not being submerged (the temp gauge usually reads over 260 before
this happens) and then sloooowwwwwly adding more fluid into the running
engine so as not to crack anything. 
There's GOT to be a better way.  Can someone help me out?

- Roel

P.S. I also don't really understand how that reservoir tank on the side
works, either.  Maybe this is part of my problem.  I try to keep it roughly
half full like the original manual says.
_

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