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how to test heater core

how to test heater core

The heater core is part of a car’s cooling system, which prevents the engine from overheating. Knowing how engine coolant flows through the system can be helpful in troubleshooting the heater core. Engine coolant travels from the water pump through a hose and through the heater core, which resembles a small radiator. The coolant leaves through another hose and passes through passages inside the engine block, where it collects heat. It then goes past the thermostat and into the top of the radiator. The coolant cools in the radiator, out another hose, and back to the water pump.

Step 1

Start the engine and see if the heater works inside the car. If heat is coming out of the vents, the heater core is effectively transferring heat from the engine to the air ducts.

Step 2

Check the radiator for coolant and the thermostat for proper function. You could have a bad heater core if the radiator is full of coolant and the thermostat turns on when the engine warms up.

Step 3

Smell the air flow from the defrost vents after the engine has been running for a minute or two. A sign of a bad heater core is the smell of antifreeze with the heater or defroster running. Also, check the passenger compartment floor. The passenger side footwell may have a small puddle of antifreeze when the heater core goes bad.

Step 4

Visually check the vents after starting the car engine and turning on the heater. When a heater core goes bad, small puffs of smoke can sometimes be seen.

Feel the hoses going to and from the heater core. If one hose is hot and the other is cold, the heater core is most likely bad.

5 Signs of Heater Core Failure and What to Do

Heater core problems are unique and not in a good way. The heater core is pretty much the only item in your vehicle that can leak inside when there’s a problem. all other components that are prone to leaking usually drip onto the floor. so heater core issues can be tricky to deal with.

Most heater core problems are the result of poor cooling system maintenance. Flushing and replacing the coolant as specified in  your owner’s manual  can go a long way in preventing problems caused by the buildup of rust particles, dirt, and depleted anti-corrosion ingredients in the fluid. Your heater core, with its tighter passages, is one of the first items that can be damaged by this dirt.

how to test heater core

There are several tell-tale signs that you are experiencing a heater core problem:

1. You have little to no heat inside your car

Your vehicle is running fine with a normal temperature gauge reading and no other cooling system problems. but when you turn on the heat, it never gets hot.

Solution:  First rule out a fan malfunction by checking the fuse, circuit, and the fan itself if necessary. If that works you can test the blend door and cab vents. Start the car, let it warm up, and then turn the air conditioning on full blast; You must feel the cold air. now raise the heat to full heat. you should quickly notice the difference and feel the hot air. You can then go through the ventilation options, including defrost and floor. If one (but not all) doesn’t work, you probably have a blend door or vent problem.

If none of these work, you can also check your  cabin air filter  , which can fill with dust and dirt, blocking airflow through your heating system. If the filter is ok, the heater core may be clogged.

The heater core is buried deep behind your dash and requires a lot of disassembly to get to. We recommend that you  take your car to a mechanic  for any heater core repair as further damage to the car is possible if they are inexperienced in this type of work.

It might be possible to clean the heater core passages with a water hose or with air pressure, but many modern heater cores have plastic pipes and tanks so this can be risky. do not exceed the pressure indicated on the radiator cap when flushing. another possibility is that the outer fins of the heater core are clogged with debris being sucked in through the air inlet. cleaning the fins may fix the problem if there are no other problems.

if this does not resolve the issue, the heater core will need to be replaced.

how to test heater core

. You smell coolant inside your vehicle

As you drive, you can detect the sweet, fruity smell of the coolant inside.

Solution:  Your heater core may be in the early stages of failure. a leak as small as a hole in your heater core can spray a fine mist of coolant inside, and you’ll smell it. Avoid stop-leak products, as they are at best a temporary solution and can cause other problems. It’s best to call your mechanic and take care of this now, before it gets worse.

3. Your windows fog up

this is a more extreme version of the coolant smell scenario. the amount of coolant coming out of the heater core is enough to form a mist that covers your windows and is difficult to wash off. This is bad, not only because it blocks your vision, but also because breathing ethylene glycol is bad for your health.

Solution:  Call your mechanic, roll down your windows, and have your vehicle repaired immediately.

4. You see signs of a coolant leak under the dash

You may notice coolant dripping from under the dash, or there may already be a large, wet spot of coolant on the front carpet.

Solution:  Check the coolant level  and top up if necessary. If there is a coolant leak inside, your engine is in danger. A low coolant level can cause the engine to overheat, which could lead to a large repair bill. Call your mechanic immediately and fix the leak. Once the repairs are complete, have your carpet professionally cleaned or replaced to remove the refrigerant smell.

how to test heater core

5. Your coolant level is getting low or your engine is hot

If you have a leak anywhere in the cooling system, including the heater core, it will cause a couple of related problems. Your car will lose a significant amount of coolant and eventually your temperature gauge will run higher than normal.

Solution:  Top up your coolant and take your car in for an immediate inspection. A refrigerant leak will not fix itself, it will only get worse. Again, if you drive without enough coolant in your car, your engine  will start to overheat  . this can quickly ruin the engine.

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