iBgodsmacked

I have a friend who just purchased a 97 impreza. He has had it for about a week and replaced the thermostat twice now. I have been telling him to back flush the radiator. getting ahead of myself.

He will drive this car for time, hour or so, fine open road but will over heart stop and go. My question is how to remove the water pump and if it would be a solution. I stand by the coolant fllush idea. please help me with some suggestions and experiances of yours