How to Troubleshoot an Auto Radiator

by Chris Moore

The radiator is the main component of the car's cooling system, which keeps the engine from overheating. If your cars begins to overheat, there are small things you can do to cool it, like shutting off the air conditioner. If the car frequently overheats, however, there is a problem with the radiator or cooling system. Air and coolant flow are important to the system. When troubleshooting a radiator, you must check the thermostat, hoses and other parts connected to it, looking for signs that might impede the air or coolant flow.

Check the water/coolant level. This is often the number one cause of overheating. Open the radiator cap on a cool engine; you should be able to see the fluid if the radiator has enough. Fill the radiator as needed; use a 50/50 mixture of water and coolant for best results.

Check for coolant dripping outside the car. A sweet smell on the outside or fresh green liquid on the ground means a leak in the radiator or hoses. Antifreeze leaking in the car is a problem with the heater core.

Observe the car's temperature while driving at highway level speeds. If the engine is overheating while driving at 55 miles per hour or more, the coolant/water is likely not circulating properly.

See if the water is circulating properly. Start the car with the radiator cap off; the water should pop over the top smoothly while still retaining its amount. You can also disconnect one of the radiator hoses and see if water is continuously flowing.

Inspect the condition of the hoses. See if they have become brittle or cracked. Check for leaks in the fittings and see if the seams have been blown.

Look over the thermostat and make sure it's open and clean, allowing water to pass through it. If it is clean but water isn't circulating, check for leaks in the water pump.

Flush the cooling system by draining all the coolant into a container through the radiator drain plug (make sure the car is cool). Siphon out any coolant that is in the radiator reservoir as well. Fill the radiator with fresh coolant and make dispose of the old stuff as environmental laws require.

Remove the radiator from the car and inspect it. Check for rust or water calcification that can accumulate within it. Clean or replace the radiator if needed.


  • close Never remove any radiator fixtures like the cap or drain plug unless the engine is cold. The water and coolant will spurt out at an extremely hot temperature and cause serious harm.

About the Author

Chris Moore has been contributing to eHow since 2007 and is a member of the DFW Writers' Workshop. He received a Bachelor of Arts in journalism from the University of Texas-Arlington.