Your radiator, which is usually mounted at the front of the vehicle or the front of the engine (depending on engine location). It is a large, square or rectangular object that transfers heat from the vehicle's cooling system to the outside air, allowing the engine to run at optimal temperatures. It is not the same as your air conditioner.
How Does the Radiator Work?
The radiator works by circulating coolant, which can be water, anti-freeze, or similar substances, through the engine core. This circulation is usually facilitated by the water pump, which is most often driven by the timing belt.
The circulating coolant absorbs heat from the engine and sends it to the radiator, which sends the hot coolant through thin pipes with radiating metal sheets coming off of them. These pull heat from the hot coolant and disperse it to air as it passes through the vehicle. This cools the vehicle's engine coolant, allowing it to circulate back into the engine and pick up more heat to repeat the process.
The vehicle carefully regulates the flow of coolant and thus keeps the engine at optimum operating temperature. If something is wrong with the radiator or coolant, the engine will not be properly cooled and may overheat or run inefficiently.
What Can Go Wrong With a Radiator?
Several things can go wrong. The most common is a radiator leak from the rubber hoses that connect the radiator to the engine core. Leaks from split seams or connections in the radiator itself are also a common problem, especially with older vehicles that have seen a long service life. The radiator may also become damaged from a collision or accident. If your engine is running at temperatures above or below optimal operating temperature (usually at the mid point of your engine coolant temperature gauge on the dashboard), then there is likely something wrong with the radiator or coolant circulation system.
How To Diagnose a Radiator Problem
Check for an obvious, visible radiator leak. If the hoses are leaking, they will require repair. This is a relatively easy DIY that any home mechanic should be able to do on most vehicles. There are two hoses (one at top, one at bottom) and sometimes smaller accessory hoses. If the radiator itself is leaking, you will need specialized equipment to weld the break. Temporary additives can fix the problem for a short time, but be aware that some can cause engine damage.
If there are no obvious, visible leaks (anti-freeze is usually bright, fluorescent green or yellow) from the radiator or its hoses, then the following steps, in order, will likely find the problem for you. They can be done by anyone at home, whatever their mechanic skill level.
Step 1 - Determine if the engine is running too hot or too cold. Do this by watching the engine or coolant temperature gauge on the dash - it usually has a thermometer symbol on it. If the engine is running too hot, proceed to step 2. If it's running cold all of the time, you most certainly need to replace the thermostat which controls coolant flow from the radiator to the engine block.
Step 2 - Make sure there is coolant in the radiator and reservoir (if any). Do this by allowing the engine to fully cool - it should be cool enough that you can lay your hand on the metal parts or the radiator itself and keep it there without burning or feeling uncomfortable. Remove the radiator cap and look inside (shine a light if needed). If you cannot see liquid inside, your radiator is low on coolant and needs to be filled, which is a simple repair. Add recommended coolant (usually 50/50 anti-freeze and water). Close the cap and place a large piece of cardboard or an old bed sheet under the radiator and engine. After an hour or two, see if there are leaks by checking your ground cover.
Step 3 - If there is sufficient coolant in the vehicle and no visible leaks, drain and flush the radiator or take it to a shop for this service. It's recommended that you replace the thermostat when you do this, as a preventative measure and because if you've gotten this far, it's likely that is the culprit. If the problem is a blockage in the radiator or cooling system, the flush will most likely push it out.
Step 4 - Use an in-line pressure gauge or have a mechanic test your coolant pressure. This is usually done at the radiator cap and on the in-line (coming from the engine to the radiator, usually at top). This will determine if your water pump is faulty.
In most cases, one of these four steps will pinpoint and alleviate your cooling system problem. If not, you'll need more sophisticated diagnostics.
photo by John Nyboer