When does it start over heating, at idle, after a run, as soon as you start up?

Is the thermostat good?
Is the fan cutting in?
Is the radiator blocked?
Has a pipe collapsed?
Is the new pump correct for your engine,,,correct rotation?

Could be cracked head or block or blocked waterway.
Failed thermostat.
Blockage somewhere.
Rad sensor faulty.
Fan faulty.

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