First thing, use an air nozzle and blow out any crud from the radiator and between it and the AC evaporator. Next go to an auto parts place or even Harbor Freight and get a non contact I/R thermometer. Start the engine and check the temperature at the pump and heater hoses. If the heater hoses start to warm up fast the pump is working. Another quick test that you can do while towing, if it heats up, turn the heat on full hot, watch the temperature gauge, if it starts dropping real quick the pump is working. This is because the heater core is more efficient at heat transfer than the radiator.
Use the thermometer to scan the radiator as well. You are looking for spots that do not warm up as fast or at all compared to the rest of the core. This can show you if the radiator is partly plugged. This should be easy to see when the thermostat opens.
Oh and if you think the thermometer is a bad tool to buy (like $25.00 for the gun version at HF) it is also great to check wheel bearings, brakes, exhaust systems and more. The wheel bearing temps can alert you to bad grease quick.
Thursday, June 29th, 2017 AT 10:29 PM