Overheating issues
Ok, then what about the Fords of the 60s? They had expansion tanks above the radiator that were on the order of about a half gallon
That tank was effectively the top of the radiator and had the pressure cap on it
(IIRC)
Thunderbirds IIRC.
My 56 Ford pickup did not have that, my 63 econoline, 65 and 68 mustang either.
The newer cars have a closed system in that the expansion tank has the pressure valve on it. And an air gap to allow for the expansion. As the pressure gets to cap pressure the fluid is well below the cap and only air is expeled or sucked back in.
JUST LIKE MY 67 WITH NO OVERFLOW.
the air gap in the top tank of the radiator tank is sufficient volume to hold the expanding fluid. As the pressure goes up it reaches cap pressure and expels air.
As the coolant cools off the and it's volume reduces it sucks (atmosphere pressure really pushes) air back into the top tank.
Not a drop of fluid is spilled, no overflow is needed.
Bottom line. If the radiator is filled 100% full the expanding fluid has to go somewhere. When the pressure in the rad gets to cap pressure fluid will exit the radiator. If it goes into a closed vessel ( no vent) it will pressurize the vessel in short order and continue to build pressure till something let's loose.
It's not rocket science. But some symantics complicates things.
In one of the OP's posts he stated that his friend confirmed that his "overflow" did not have a vent, and that he was going to reroute his line from the rad to the bottom of the "overflow" and drill a hole in the cap for a vent.
