Thread: how often do water pumps fail but not leak?

My cousin's 1992 Mazda MX6 with 2.2 liter 4 cylinder, manual transmission, AC, 275,000 miles that just recently started to overheat but recovers on its own temp goes up while driving on highway at 70 mph and then goes back to normal, on flat road.
How often you guys, have seen a water pump quit pumping? Will a blocked heater core this motor to overheat?

I don't know about the heater core issue. If it is blocked off in a dead end try looping a hose from it output to its input on the engine. The first thing that I would do is check and fill the radiator when the engine is cold. Don't try to do this when the engine is hot. You could get burnt, and the cool water could damage the engine. Because of the high miles on the car I would also check it for a blocked radiator. If its plugged up get it cleaned, recored, or get a new one. fill it with a 50/50 mix of coolant using distilled water. Also check that the water pump belt is tight. And last but not least check the operation of the thermostat. If in question, ditch it, and get a new one. There are other issues that could cause your problems too. We don't even like to think about them. On a hi miles cars the headgasket can always be and issue. Do you have any water in the oil? Does the car blow heavy white smoke that just hangs in the air for a long time? Does is have a misfire? All these things could indicate a blown headgasket. And one other thought. Check the lower radiator hose. Some have a wire coil in them so the water pump can't suck them closed. If the cooling system has been neglected this coil can rot out, and let the hose get sucked closed at higher rpms.