1999 ranger coolant problem

[shaffer93]

i have a 99 ford ranger 4x4 3.0 flex fuel that the temp gauge will read normal then it will drop a little and go straight to hot. I've replace upper and lower hoses, theromstat, waterpump and radiator and had it flushed. when it gets hot it will push out of resevoir. its not leaking any where. the only thing i haven't replaced is the heater core and hoses. I'm not sure what else to check.

[MAKG]

That's far from the only thing you haven't replaced.

If the system makes any knocking noises after a warm engine is turned off, it isn't full.

Otherwise, run a leakdown test.

[shaffer93]

There's no noise after i shut it off.

I will try the leakdown test

thanks