I have a 2010 toyota prius. The coolant light started coming on a couple of weeks ago intermittently and I had no heat. I have since replaced the water pump with 2 amazon specials and an OEM Asin. I've replaced the thermostat (Duralast), the coolant temp sensor(Duralast) and the Radiator with a used one from the junkyard. I'm still getting the same issues after replacing everything in the cooling system except the heater core. That's the next thing I can think of maybe trying to flush it, but I'm really at a loss and wondering if anyone else has experienced this and had a resolution that I can try. The car has not overheated and I have not driven it other than to troubleshoot if the issue has been resolved. I don't want to continue to throw money at good parts guessing. The radiator thermostat and temp sensor were replaced by a mechanic I've changed the water pumps.
You should use an OBD2 scan tool OR a Bluetooth dongle and use an app to monitor the engine coolant temperature. Has the coolant in the plastic reservoir gone down? When you said that you replaced the water pump with an OEM Aisin, I am assuming that you did not buy the OEM pump from a Toyota dealership. I think you still have a water pump problem.
I'm at 300k I've had it for a year put over 50k on it in the last year. The air still comes out ice cold with the heat on high, coolant doesn't leak either, but coolant light will flash on and off.
Normally I would agree, but it's been 4 water pumps that I've tried, and I can feel the water moving through the hose when I put my hand on it.
^ That and check your coolant temperature sensor. It's actually a variable resistor, so a bad or corroded connection will affect it's output reading. Also inspect for rodent chew marks on your wiring harness. Hope this helps...... Did you also compare hose temperature to radiator temperature with a laser temperature gun? Cold spots in the radiator would indicate a blockage. Make sure your electric cooling fans are operational also. Have you been changing the coolant every 50K miles, before replacing the water pump 4x? One of the previous owners may have put a stop-leak product in the coolant and it's now clogging up the coolant pathways.
