[DeTomaso] gumball pantera overflow water tank question

[Larry Finch]

 Bob,

IMHO, you went wrong when you added coolant to the pressure tank.

And wrong again by leaving it open.

Now this is fine for the initial fill of an empty system. In fact, that is how it should be done.

 
But from your post it appears you were 'topping off' the system. The overflow tank is the tank you should use for that task.

When the system is filled, and at equilibrium, most owners keep the overflow tank 1/3 to 1/2 full. That leaves room for expansion
when the coolant is hot.

In a well-sealed system, there will be a vacuum created as the engine cools, and that will suck coolant out of the overflow tank
and eventually create a fully-filled system. With air well bled out at the initial filling, and several hot-cold cycles, the coolant system
should be purged of air, and also be fully filled.

I use a small diameter wooden dowel as a dipstick to determine the coolant level in the overflow tank. You can check to confirm a
full system by pulling the pressure tank cap when things are fully cold.

Just to complicate things perhaps a bit more, when I am filling my empty system, I open a top bleed on the radiator and have the
engine block pipe (The one with the thermostat) unbolted.  This is not really too much work, as a new thermostat for an empty system is easily
done at that point and is just good, cheap insurance. I fill through the pressure tank until the radiator spills coolant and close that bleed.
I continue until the coolant reaches the thermostat area. 

BTW, unless you are in a COLD climate, a 25%-33% anti-freeze mixture gives
plenty of freeze protection, and is a better coolant than a stronger mixture.

Larry