Heater Core Replacement

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How to Bypass Your Heater Core

Your heater core has two hollow tubes (an inlet tube and and outlet tube) that extend from the interior of the vehicle and through the firewall to the engine compartment. In the engine compartment, coolant hoses attach to these tubes. Hot coolant flows from the engine and into the heater core through the inlet hose. The coolant passes through the heater core (dissipating nice warm heat to the interior of the vehicle) and then it flows out of the heater core through the outlet tube.

This simple system works great until the heater core starts to leak. When this happens, you basically have four options. The first one is our recommended action. If you can't replace the core immediately, then number 2 is the best option.

This page offers a quick and easy way to accomplish number 3 if 1 and 2 are not realistic for you at the time. Number 4 should be reserved for idiots. 

1. You can replace the heater core right away
2. You can park the vehicle until you can replace the heater core
3. You can bypass the heater core and continue to drive it for a short while until you can replace the heater core
4. You can just keep pouring fresh coolant into the radiator and go on driving like a deranged Ninja till you die from an accident caused by the steamed windows or from any one of the many diseases caused by breathing these toxic fumes.

First, let's talk about option 4 and why we DO NOT recommend this option.

When your heater core fails, it is always best to not drive the car until you can replace the heater core. There' are many reasons why you shouldn't drive it if the heater core is leaking, including:

• The vapor that comes from the heater core is toxic.  You really don't want to breathe this toxic cloud. In addition, every time you drive it, this toxic mist is being absorbed into your skin, clothing, hair, vehicle upholstery, etc. This transforms your vehicle into a toxic site that will last far beyond the heater core problem. Don't do it. 
• The vapor will condense on the windshield and all windows in the vehicle, making it almost impossible to drive safely due to restricted visibility. 
• The leaking coolant is saturating your carpets every time you drive. Also, take a look under your vehicle at what it is doing to your garage floor. 
• The coolant is being constantly depleted due to the leak, so you run the risk of engine damage due to overheating. 
• The hot steam is condensing on and in your sensitive electronics throughout the vehicle. It's only a matter of time before your computer or other expensive electronics malfunction. Even our heater core site can't help when that happens. 

The list goes on and on, but you get the idea. Our recommendation is simply don't drive it till the core is replaced. However, if you have no other options other than to drive it, you can eliminate most of the above problems by simply bypassing the heater core. The down side to this is that you will have absolutely no heat in your vehicle.  This may not be a viable band-aid if you drive in the colder climates. 

If you so choose, here is how it's done:

1. Raise the hood and disconnect the negative battery cable. 
2. Locate the heater hoses. Most vehicles will have two heater hoses. Both hoses will be connected to tubes (normally located on the passenger side of the vehicle) which go through the firewall and into the heater core.  
3. Drain about 2 gallons of coolant into a clean container for reuse. (If you don't drain the coolant, you will create a toxic puddle under the vehicle when you detach the heater hoses.) 
4. Disconnect the heater hoses from the heater core tubes. Most heater hoses are connected to the tubes with screw-type hose clamps. You can remove these by simply loosening the clamps with a screwdriver.

                      

5. Other vehicles will have squeeze-type clamps that can be removed by squeezing with pliers.
   
6. Many vehicles will have connectors inside the ends of the heater hoses. These can be difficult to remove without a special tool designed specifically to remove them. It is easier to simply cut the heater hoses off about 4 inches from the end. This is especially true if you plan to replace the heater hoses when you replace the heater core. If you don't plan to replace the heater hoses, you can simply repair them with the heater hose repair kit. The remaining 4 inches of heater hose still attached to the heater core can be easily removed later after the heater core is removed from the vehicle. Here is an example of the heater hose connector on a 1999 Ford F1-50 (after removal from vehicle).

 

7. Simply join the two heater hoses together using the heater hose repair kit or small diameter plastic tubing (if you decided to cut the hoses from the heater core, be sure to join together the long hoses coming from the engine, not the short hoses still attached to the heater core). Connecting these hoses together allows the coolant coming from the engine to properly return to the radiator without flowing through the heater core. (In this photo, we have joined the two hoses with a backflush fitting. This provides a garden hose connection that can be used to backflush the cooling system and/or the heater core.

8. Tighten all clamps and replace the coolant that you drained from the system.

9. Start the engine and check for leaks. If the heater hoses are connected properly and clamps are tightened down, the system should contain no leaks. Allow the vehicle to reach operating temperature (so that the thermostat is allowed to open) and closely watch the connection points. Feel the hoses to ensure they are getting hot if no leaks are detected. If there is a leak and a slight tightening down the hose clamp doesn't stop it, a small amount of RTV silicone may be used on the plastic connector to help seal the connection. Allow the system to cool and release the pressure before working on any heater hoses.

NOTE: After doing this procedure, remember that the heater and defrost system in the vehicle will no longer work until the heater core is replaced and properly connected again. 

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