My Chevrolet Caprice Classic 4.3L is trying to overheat, the temp. Climbs after warm-up. I already replaced the Water Pump, could it be a faulty thermostat or ECT sensor?
When I pulled out the ECT sensor out of the old water pump, I cleaned it with a wire brush and it looked okay. Also, I put a new thermostat gasket on. Maybe the thermostat got ruined from excessive heat? When I added water to the system after replacing the water pump, I didn't bleed it, could there be air in the system causing slight temp. Climbing?
The first thing I would have done would have been the thermostat. Replace (or remove and test it. Direction on homepage / DIY section). As far as bleeding the system, there could be an air lock. You should bleed it.