boiling after 3 miles but...

Moparbaker said

When I notice the temp is rising there's water squirting out bigtime & that's when I stop & refil with about 5-6 liters & then it's alright. So yep: there's water under the car + a track behind too.

The thing I really wonder about is why it's alright after the refill?
It's as if the cap don't let out the warm air & then it overheats fast in this hot weather, 25-30 C / 77-86 F.

Click to expand...

If you have a return type cap you might get another one.
Sometimes the return valve hangs open as the system is cooling down from the last drive and then sticks letting the coolant bypass it before the cooling system gets up to pressure.

If you don't have a return (aka recovery system) you should get one.
The recovery system keep the cooling system completely full all the time when working correctly, and that little valve closes tight a lot better when coolant is up against it instead of air.