When you start your car engine and it begins to warm up, you will notice warm air flowing in and circulating in the car. Ever wondered where the warm air comes from?

Well, it comes from the heater core behind the dashboard. There are two hoses connecting it with the engine – the feed pipe and return pipe. The feed pipe carries the hot coolant from the engine to the heater core. And the return pipe carries the coolant back into the engine.

As the hot coolant flows into the heater coil, heat radiates from the small piping. To improve circulation, the blower motor turns the fan and blows warm air in the cabin.

The heater valve controls the temperature. When turned on, the heater valve allows the hot coolant to flow into the core and when shut off, it bypasses the core. In this case, cool air blows in the cabin.

There are occasions when you turn on the heater valve, and nothing happens. This is a clear sign your heater core has a problem or is underperforming.

Want to know other telltale signs that you’re in need of heater core repair? Here are the top five.

1. You Can Detect the Fruity Smell of Coolant in the Car

Immediately you sit in the driver seat of your car, you will note plenty of other smells. Some of these smells are normal while others are not. If you are keen enough, you will detect a pungent smell which is evidence that something is wrong.

If you warm up your engine and detect a sweet and fruity smell from the vents, that is the coolant. The antifreeze or coolant is the main ingredient that keeps your coolant system and car cool. If the odor is strong inside the passenger compartment, it’s a sign you have a bad heater core.

Antifreeze contains ethylene glycol. This is a toxic substance and what makes the coolant have a sweet and fruity smell. When you detect the fruity smell, it could be from a small leak the size of a pinhole along the feed pipe or heater core.

As the coolant flows through the feed pipe to the heater core, it passes through small pipes. If the leak is along the small piping, the heater core can spray a fine mist of antifreeze into the cabin. This is how you detect the sweet and fruity smell of coolant.

I recommend that you drive your car to the nearest mechanic if you detect a sweet and fruity smell. You can perform heater core repair in your garage by replacing hoses and tube fittings. When shopping for hoses and tube fitting,  buy quality products only.

2. Antifreeze Is Dripping down from Under the Dashboard

Another sign of a damaged heater core is leakage of coolant from under the dashboard. As said earlier, the location of the heater core is behind the dashboard on the passenger side. If your heater core is leaking coolant, that means the coolant level is low.

As such, the engine can overheat. This is one of the main causes of mechanical breakdown. If the leak is small, you will notice a tiny trace of the antifreeze under the dashboard. You may also find a sizeable puddle instead of a small leak.

The sizeable puddle on the passenger floor forms when the engine is cool. If this happens and you notice that your car has an appetite for coolant, your engine will overheat.

To avoid a mechanical breakdown, have the issue fixed immediately.

3. Your Windows Are Fogged Out

Apart from the smell of coolant, fogged out windows is another sign of a damaged heater core. You need to note that I am not referring to mist at the end of your car windshield. I am referring to warm condensation covering all the windows.

As said earlier, the heater core connects to the engine by two pipes – feed pipe and return pipe. Hot coolant flows from the engine via the feed pipe into the heater core. If your windows are fogging, it means the feed pipe is leaking.

It could also mean that the small pipings in the heater core have a leak. Instead of hot air blowing into the cabin, the hot coolant leaks and evaporates into steam. The cool air in the car condenses the hot coolant.

This is how your windows become fogged out. If you notice this, switch off the engine and call your mechanic. You don’t want to drive and breathe in the toxic coolant. To repair the hoses and tube fitting, buy a heater hose repair kit.

4. Having a Cold Car Cabin

If your engine is running hot and the heater level is warm or hot and yet the cabin is cold, you have a damaged heater core. It could also point to other issues close to the heater core. For instance a damaged blower motor or failure of the coolant system.

If the issue is a damaged heater core, it means warm air is escaping before getting to the heater core. To find the source of the problem, check for coolant leak under the dashboard or elsewhere.

If the issue is not with the coolant, investigate other components such as the blower motor, or fan. It is important to understand that overheating is a serious problem. If it occurs, major components in your car will not only wear out but may break down. And you know what that means.

More repairs and replacements. The cost of repairing or replacing parts is exorbitant. Next time your car temperature gauge reaches the danger zone, don’t drive your car. Have it towed to the mechanic.

If you don’t, well, I don’t have to tell you the consequences.

5. You Car Heater Is Not Working

A non-functioning heater is a major red flag that you have a damaged heater core if your car is running fine. If the temperature gauge reading is normal and fuses have no issues, the culprit is the heater core.

To be sure, start by checking the fuse. This allows you to rule out any issues with the blower fan. Next, test the cabin vents. Start your engine, allow it to warm up for a minute and turn the heater lever to full blast.

If the system is ok, you should feel a  blast of cool air. Now, turn the heater lever to full heat. If you feel warm or hot air flowing into the cabin, your heater core has no leaks. Try other venting options to be sure.

If the heater core is not the culprit, the cabin air filter might be. Dust and dirt can block airflow but if it’s ok, then the issue is with the heater core. As said earlier, the heater core is behind the dashboard. To replace it, you have to disassemble the dashboard.

Unless you are a skilled mechanic with the right tools, drive to the nearest mechanic. Not only is he skilled in disassembling the dashboard, but he can flush the small pipings of the heater core. Cleaning with heater core cleaner may fix the issue.

If not, heater core replacement is necessary.

Heater Core Repair Best Advice

If your car windows are fogging for no reason, and your engine is overheating, you have a damaged heater core. Other telltale signs include a fruity smell in the car and a cold cabin. Our best advice – drive to the nearest mechanic. Don’t attempt any DIY heater core repair unless you have the skills and experience. Doing so might escalate the damage.

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