How to Perform a Heater Core Bypass (Step by Step)

When your vehicle’s heater core pulls out, you might need to perform a heater core bypass so that the cooling system can keep functioning and prevent the coolant from dropping on the passenger compartment.

Doing this is not so difficult, but the right tools should be available to successfully perform a heater core bypass.

This article explains how to properly perform a heater core bypass, the pros, and cons of a heater core bypass, when you should bypass the heater core, and lots more.

Let’s begin!

One technique used to fix your heater core in a car’s engine is a heater core bypass. The heater core generates heat in your car during Cold weather or Winter.

Still, there is a possibility that the heater core could leak, resulting in a leak of coolant.

Hence, you can either purchase a new one, replace the damaged one, or fix it when such happens.

If you are fixing the heater core, the most common method used is bypassing, saving costs of repairing the damage.

Also Read: How to Bypass Reduced Engine Power (Step by Step)

How To Bypass the Heater Core?

How To Bypass the Heater Core

Step 1: Take Out the Dash Board Cover or Air Conditioning Grating.

For you to reach the heater core, it would be necessary to remove the dashboard cover, but you might be able to do it by just taking out the Grating when the gratings are where they should be.

This is based on which of the heater core is dripping or if it is directly at the back of the Grating.

Step 2: Remove the Hoses

There are two hoses running into your heater core, one for the antifreeze and one to return to the engine.

When there are clamps in these hoses, they would be easy to remove. If not, you’ll need to cut it.

When you cut them, ensure you do that close to your heater core to increase the length of the hose remaining that you will work with.

Don’t start working when your heater core is still hot; patiently wait a few hours after turning off your engine to allow it to cool.

Step 3 – Join the Hoses Together

Use a hose coupler or hose connector to join both ends of the hose together. This way, it would make the antifreeze passing through your heater core pass through a tube made of a short loop instead.

You can get these hose couplers or hose connectors inside a hose repair kit in an auto supply store.

When you bypass your heater core, the interior heating system disables and rejoins before Winter.

The process is relatively complicated, and getting a professional to do the job costs hundreds of dollars.

Check out this video for more tips on how to bypass a heater core

Why Would You Need a Heater Core Bypass?

There are several reasons why people would want to perform a heater core bypass; they include:

1. Coolant Leaks

Heater cores are mainly for diverting hot coolant to your car’s cabin. If your heater core is damaged, it will start leaking the coolant inside your car’s cabin rather than maintain the car’s heating system.

In this situation, a heater core bypass is advised.

2. Unclear Windshield

Your windshield can also be affected if the heater core is not working properly; the coolant would start leaking on the windshield.

Again, this would increase the car’s safety risk. Performing a heater core bypass might be needed to do away with this risk.

3. Overheated Car Engine

A damaged heater core tends to leak coolant on the windshield and cabin. The function of this coolant is to ensure the heat of your engine is kept at an average level.

When the coolant begins to leak on the windshield and the cabin, the coolant remaining inside the cooling system will not be enough.

These cooling systems will fail to function properly if there’s not enough pressure from the heater core. This naturally would cause your engine to overheat.

If you want to prevent your engine from being overheated, performing a heater core bypass might help.

Also Read: How to Perform Neutral Safety Switch Bypass (Step by Step)

Is It Wrong to Bypass the Heater Core?

The Heater core sometimes might stop working, leading to drops of coolant in your car’s cabin.

For this situation, you need to fix your heater core. But some persons decide on bypassing the heater core to avoid the cost of repair as this is cost-effective.

Professional help is recommended when you are bypassing the heater core. If you don’t, the car’s heating system could be damaged.

This can also result in issues with the car’s windshield defogger system.

Technically, when the heater core is bypassed, it means you have taken away your car’s privilege for heating.

But unfortunately, this also gives up extra safety procedures by compromising your windshield defogger system.

Considering all this, when you bypass your heater core, it can be an unpleasant thing to do since it poses a threat to your car.

Side Effects of Heater Core Bypass

Side Effects of Heater Core Bypass

After bypassing the heater core, there are some side effects. Which are:

1. Lack of Heat

One major function of your heater core is that it generates heat for the car’s cabin.

After performing a heater core bypass, your car’s heating system will not function. Hence, you will begin to freeze in your car in Winter due to the absence of heat.

So Instead of bypassing your heater core when left in cold weather, it’s better to fix it.

2. Threat to Windshield Defogger

The car’s windshield defogger system could stop working after you perform a heater core bypass.

In cold conditions, your heater core helps to prevent your windshield from having fogs.

When your windshield defogger is bad, driving with it can lead to an accident.

In this case, one clever thing to do is to fix your heater core since bypassing can result in more threats.

3. Development of Rust and Corrosion

Leaving the bypassed heater core idle could result in the development of rust and corrosion.

In addition, fixing the heater core costs much less compared to the cost of swapping it. This means you won’t be able to fix it if your heater core is bypassed and gets rusted.

In such a situation, fixing the heater core would be preferred.

Cost of Heater Core Repair

The average cost of fixing the heater core range between $550-$1,000. If you visit sites like AutoZone, which supplies parts, the heater core itself costs around $25 to $150.

Fixing the heater core is somewhat an expensive thing to do. But, like any car repair job, the cost depends on the model, make, and year of the vehicle.

Also Read: Car AC Smells Like Vinegar (Causes & Solutions)

How to Maintain the Heater Core

Heater Core Bypass

Taking proper care of the important parts of the heater core and the cooling system will save you a lot of money.

Taking proper care of your heater core would also help increase your heater’s durability and efficiency.

Replacement of the coolant device or heater should be done regularly by the owner for at least every 2-3years.

Also, from time to time, stay alert regarding the fault that might arise from the heater and look for solutions immediately to repair a damaged core.

For proper maintenance of your heater core, visit an auto shop for proper services.

The auto repair workers and technicians are professionals and skilled in maintaining all the important components of the engine.

Frequently Asked Questions – Heater Core Bypass

Is It Ok for You to Bypass Heater Core?

When you bypass the heater core, Basically, you are taking two hoses from your heater core and sticking them together. In this way, coolant continues to circulate, even if it doesn’t pass through the heater core. Bypassing your heater core should not affect the efficiency of the car’s engine.

Why Would You Bypass the Heater Core?

When the heater core is leaking, bypassing might be necessary. The cooling system radiator can start developing holes resulting in coolant leakage. Apart from the fact that the heater would not function properly during Winter, it also means that the car would lose its coolant.

Would the AC Work Without Heater Core?

The ac system should not be affected when you bypass the heater core since it has a valve that shuts off the flow going into the core when not used.

Will the Radiator Flush the Unclog Heater Core?

Definitely, both are components of a cooling system, and similar coolant passes through them. Rusts that pass through its heater core can be reduced by flushing the radiator. Flushing with the help of a garden hose is the most effective method for unclogging the heater core.

How Much Does It Cost to Repair the Heater Core?

To have the heater core repaired by a professional would cost about $800-$1000 for both the parts and labor. The labor cost varies, so call beforehand and get a quote from different repair shops. When you repair the heater by yourself, you will just need to pay for a new heater core which ranges from around $100 to $300.

Does the Heater Core Have an Effect on Engine?

When you have a damaged heater core, driving could be risky as this can result in extensive damage to the engine and overheating. When the heater core is clogged, it could prevent proper circulation of coolants causing the engine to overheat. If you have to drive for some time, ensure you check your temperature gauge from time to time.

Will Heater Core Make Your Car Overheat?

A clogged heater core, in most cases, does not lead to overheating. Regardless, when other problems are added, the engine can be overheated. This is mostly the case if the cooling system’s efficiency is already compromised, just like in a partially clogged radiator or a damaged water pump.

Conclusion – Heater Core Bypass

Bypassing a heater core in the car is an easy job for a mechanic. When you have the skill and enough confidence to change the oil filter in the vehicle, then you can handle the bypassing of the heater core.

However, you also need to know that bypassing your heater core is just a temporary repair to a problem.

So while your Cooling system is still functioning properly for the engine, you need to know about the potential effects this will have on the vehicle’s cabin.

Getting the heater core repaired, especially in cold conditions, is needed instead of leaving it bypassed for long.

Scott Greene is a seasoned automotive technician for over 5 years and has been deep into advanced automotive diagnostics for a couple of years. He Loves writing about Automotive Diagnostics and Repair, Trouble codes, Buyer guides for various car parts and accessories, and lots more. 

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