Should Both Heater Hoses In A Car Be Hot? (2023)

A heater core plays an essential role in keeping your vehicle's interior warm. However, if your heater isn't working correctly, could it be due to both heater hoses being hot? Let's look to see if this is a concern or not.

To properly warm the interior of your vehicle, then both heater hoses should be hot. If one is noticeably hotter than the other, then there could be a clog in the hose. In addition, if the heater hoses are cold, this is also a sign of clogged hoses.

Troubleshooting a heater core or any mechanical part in a vehicle can be challenging. This article will take a closer look at the purpose of heater core hoses and the warning signs of an issue. In addition, we will answer other frequently asked questions about heater core hoses, so read on!

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Should Both Heater Hoses In A Car Be Hot? (1)

Should Both Heater Hoses Be Hot?

The heater core is responsible for the overall temperature of your vehicle's interior. It does this by heating the air that passes through it. To do this, both heater hoses should be hot.

The heater hoses pass coolant from the engine to the heater core. The heated coolant then warms up the air and circulates it through the interior of your car. When this happens, both heater core hoses should be hot.

If you are experiencing issues with your heater, the problem could stem from the heater core hoses. First, check the temperature of the hoses, and if one is significantly hotter than the other, you may have a clog.

You can clear out the hoses or hoses by using water and air pressure. If you are not comfortable doing this, you can take your car to a mechanic.

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Should Both Heater Hoses In A Car Be Hot? (2)

What Does It Mean If Both Heater Core Hoses Are Cold?

If your heater core hoses are cold, you won't get warm air blowing through vents. Let's take a look at the most common reason this is happening:

Clogged Heater Core

If there is a clog in the heater core, the coolant can't flow through it properly. This will cause the hoses to be cold, and your car's interior won't be warm.

You will need to flush the system to get it working properly to fix this. When doing the flush, be sure to flush it in the opposite direction of normal flow.

Failed Thermostat

If the thermostat gets stuck in the shut position, it will prevent the coolant from flowing through the system. This will cause the hoses to be cold, and your car's interior won't be warm.

You will need to replace the thermostat to fix this, but this can be a complicated fix. Therefore, it is a good idea to take it to a mechanic for this one.

Coolant Leak

There is no way to heat the interior cabin if there is a coolant leak. Check for any leaks and have them sealed as soon as possible. Having a coolant leak can also damage other parts of your car.

Closed Heater Core Valve

The heater core valve may bestuck closed. If this is the case, then the coolant won't produce warm air.

Should Both Heater Hoses In A Car Be Hot? (3)

(Video) Common Problems with a Car Heater Core Hose

How Hot Should Heater Hoses Get?

Typically, you check the heater hose's heat temperature by feel. The reason is that it is hard to check the inside temperature of the hoses. However, you can check the air around the hoses to ensure that hoses are functioning properly.

The air around the heater hoses should be 85 degrees. If there is a big difference in the temperature, there is likely an issue with the hose.

How Do You Test A Heater Core Hose?

There are a few different ways to test a heater core hose. One way is to use a thermometer and measure the temperature of the hoses.

Another way is to look for air bubbles in the hoses. If there are air bubbles, then it means that there is an obstruction in the hose.

However, the best way to test the hoses is to feel them. If one is cold and the other is hot, there is likely an issue with the hoses. Lastly, check for any cracks in the hoses that would cause a leak.

What Is The Heater Core Hose Connected To?

The heater core hoses are connected to the heater core in the dashboard. The engine is responsible for providing the coolant, while the heater core is responsible for heating it.

You can trace them to the thermostat and radiator on the other end of the heater core hose. The thermostat is responsible for controlling the temperature of the coolant, while the radiator is responsible for dispersing it.

So if there is an issue with any of these parts, it will likely show up in the hoses.

What Are Heater Core Hoses Made Of?

The heater core hoses are typically made out of flexible rubber. The flexible rubber enables them to withstand the vibrations of the vehicle.

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The flexible rubber can withstand high heat, coolant chemicals, and high pressure. This makes them a very durable and long-lasting part of the car.

Can A Heater Core Hose Make A Car Overheat?

A heater core can't cause your car to overheat. If your vehicle is overheating, it's likely because of another issue, such as a clogged radiator. Also, in the case of a coolant leak, it can cause the engine to overheat.

If you are experiencing these problems, it's best to take it to a mechanic to get it fixed. They will be able to diagnose the issue and fix it properly.

Should Both Heater Hoses In A Car Be Hot? (4)

Why Is My Car Heater Not Hot?

Besides issues with the heater core or heater core hoses, there are other reasons why cool air is blowing from the car vents. Let's discuss each possible reason:

Low Coolant Level

Coolant plays an important role in the heating of your car. If the coolant level is low, it will not produce enough heat. Check the coolant level and add more if necessary.

Jammed Blend Door

The blend door is responsible for regulating the air temperature that comes out of the vents. If it is jammed, then the air will not be warm.

Faulty Blower Motor Control Module

The blower motor control module is responsible for turning the blower motor on and off. If it is not working correctly, then the blower motor will not turn on, and the car will not be able to heat up.

Bad Blower Motor

The blower motor is responsible for blowing the hot air into the car. If it is not working properly, then the vehicle will not be able to heat up.

(Video) How to Fix a Car with No Heat (Easy)

Should Both Heater Hoses In A Car Be Hot? (5)

What Are The Symptoms Of A Bad Heater Core?

If you are trying to determine if the heater core is the source of the problem, there are a few symptoms that you can look for.

Fog Inside Car

If you are running your defrosters, but your windows are fogging up, then it could be a sign that your heater core is failing. It is also possible that the heater core is blowing smoke through your vents. Both are something that needs to be addressed as soon as possible.

Sweet Smell Inside Car

If there is an abnormal sweet smell coming from your vents, then it's not a good sign. It may smell sweet, but it could mean a coolant leak in the hoses.

Cold Cabin, Hot Engine

If the engine is running hot, but the cabin is cold, it could be a sign of an issue with the heater core. This could mean a clog in the line or that the thermostat has failed.

Final Thoughts

If you are experiencing any of the symptoms listed above, it is best to take your car to a mechanic for further inspection. Waiting to address this problem could lead to your engine overheating resulting in additional repairs.

A certified mechanic will properly diagnose the issue and fix it. If you try to fix it yourself, you may end up causing more damage. Always be safe and let the professionals handle it.

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How hot should my heater hoses be? ›

Check the temperature of the heater inlet and outlet hoses by feel. (The air temperature around the hoses must be at least 85°F (24 °C).

What does it mean when both heater core hoses are hot? ›

If both heater hoses are hot then the core is getting hot coolant flowing through it. You should check the temperature blend door actuator behind the glove box on heater case to see if it is operating the temperature blend door or not. If the actuator is not moving then replace actuator and retest the heater output.

Why are both heater core hoses cold? ›

The three possibilities are stuck open thermostat, stuck closed heater hose valve (if there is one) or plugged core.

How do I know if my heater core is blocked? ›

A noticeable difference in airflow could indicate that the heater core fins have been clogged and are restricting airflow.
Heater core failure symptoms
  1. Weak or no airflow.
  2. Cold air (not warm) coming through the vents when the heater is on.
  3. Coolant leakage visible inside the cabin or a damp smell.
Mar 25, 2021

Should both heater core hoses be warm? ›

When the vehicle is at operating temperature feel the two hoses, the should be the same temperature. If one hose is noticeably hotter then the other then the heater core may be partially plugged or restricted.

Should both car radiator hoses be hot? ›

If the heater is on, both the ingoing and outgoing heater hoses should be close to the same temperature. If not, it might be time for a repair. If the upper radiator hose already gets hot before the engine has properly warmed up, it means the thermostat is not closing properly or even is constantly open.


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