I have a 1989 Pontiac Bonneville that is running hot after water pump replacement. I found out that after replacement I should have driven it to seal the gasket. Was that too damaging or could it be something else...thermostat or sensor.

WELL HOPE YOU PUT GASKET SEALANT ON WATER PUMP GASKET IF NOT.WATER PUMP GASKET WILL LEAK AND CAUSE LOST OF COOLANT LEADING TO ENGINE OVERHEATING.IF YOU DID USE SEALANT.CHECK COOLANT LEVEL STILL COULD BE LOW BECAUSE YOU HAVE TO DRAIN OUT ALL COOLANT BEFORE YOU CAN REMOVE WATER PUMP.IF COOLANT LOW ADD MORE WITH ENGINE IDLING AS THERMOSTAT OPENS COOLANT WILL KEEP DROPPING UNTIL YOU HAVE THE RIGHT AMOUNT OF COOLANT IN THE COOLING SYSTEM.IF CAR STILL OVER HEAT REPLACE THERMOSTAT AND RADIATOR PRESSURE CAP.

First off you never have to drive to seal any gasket! If it did not run hot before the replacement of the pump it should not run hot now unless something is defective or improperly installed.Presure test the system for leaks first and repair any leaks before doing anything else.Be sure to make sure that the Head Gaskets are not leaking as well!