When the radiator isn’t working properly, you might notice several symptoms. While this isn’t an exhaustive list, here are the most common complaints.
1. Overheating engine
A common sign that something is wrong with the radiator is when your engine starts to overheat. This can be caused by a faulty thermostat. When a defective thermostat no longer opens, the engine will overheat and cause a breakdown.
You might notice coolant leaking under the vehicle. It can be a red, yellow, or green fluid. When the radiator is leaking, coolant levels become too low, and when there isn’t enough coolant to reduce the heat, the engine might become too hot.
Radiators are made of metal and plastic. And because plastic isn’t as durable as metal, it’s typical for these components to become brittle and start cracking—hence the leaks.
If you have an integrated transmission cooler, you might notice trouble with shifting as the fluid becomes contaminated with coolant.
3. Shifting issues
If you have an integrated transmission cooler, you might notice trouble with shifting as the fluid becomes contaminated with coolant. This problem stems from cracks and faults in the system.
4. Fluid discoloration
Vehicle coolant is commonly bright yellow or green. Sometimes it can be pink or red. It flows freely between the radiator and the coolant passages located in your car’s engine.
If you have a bad radiator, deposits and sludge can contaminate the coolant and turn it into a rusty color—it may even look like oil.
Look in your coolant overflow tank and inspect the color. If it’s contaminated, it may also appear thicker. This causes trouble with the flow and leads to a clogged radiator.
A radiator flush might be a solution in this case.
5. Exterior fins blocked
Radiators need maximum airflow for proper cooling. The thin tubes running in the front, the ones that look like fins, carry the hot coolant away from the engine. When you drive, air passes over the fins to lower the temperature of the coolant.
If these fins become clogged by debris, leaves, bugs, or dirt, airflow can become compromised. The coolant can’t go down in temperature as it should.
With many vehicles, there is enough room to spray off the radiator with a garden hose to keep the air flowing freely.
In addition to blocking the air, it’s also possible that you have damaged or bent fins. They are delicate, which means any flying dirt or debris could lead to damage. It’s also possible that you damaged them during installation or while spraying water on them (particularly if the water pressure is too high).
If you have damaged fins, a clog can occur in the radiator, leading to an overheating engine.
6. Passenger heater not functioning
Another noticeable sign of a bad radiator is when your heater doesn’t work as it should.
Your cabin heater relies on the hot coolant that passes through the core. This produces the hot air that gets blown into your car. If your radiator is leaking or is clogged, you may not get the heat you need on that cold winter day.
Sometimes, this is just a bad thermostat too. At the dealership, we checked both when a car came in with this complaint.