can someone explain to me

[walshja]

why when I removed the coolant fill plug on the radiator, coolant spilled out? and I would say at least a cupful, and more would have come out if I let it.

if that's the high point in the system, and is the filling point, how could coolant spill out ?

and how do I get that cupful of coolant back in !!!

 

[Baz]

Was the engine warm Joe?

 

[SilentUnicorn]

the heater core
is actually just a bit higher (at least on my car) put the cup that spilled out in the expansion tank.

mark

 

[walshja]

it was warm, just warm, would that expand the coolant enough to cause the overflow?

so I should let is sit overnight before opening up the fill plug. I should have know this . . .

 

[Baz]

If it was warm enough for the thermostat to open, then pressure may have just pushed that stuff out.
It is recommended to leave it sit a while before opening, overnight isn't necessary, but an hour or so should be fine.