Heater Core Replacement


heater core replacementHeater core replacement is one of those jobs where the parts are relatively inexpensive so it may seem like a simple job, but in reality, it usually ends up being a very expensive undertaking due to high labor costs.  Heater cores can require replacing either because they get clogged or because they start to leak.

If your heater core ends up clogged you can try flushing your cooling system to remove the clog and get coolant flowing through your system again.  You can identify a clog in your heater core by checking the inlet and outlet temperatures at the heater lines going through your firewall.  If there is a large difference in temperature (more than 10-20 degrees) when the heater is off then you most likely have a clog. If you cannot unclog your heater core by flushing it then you must replace it.

The other problems heater cores have is leaks.  Leaking heater cores often result in coolant dripping from your AC condensate drain or onto the passenger side floorboard.  While these leaks are usually slow enough that they won’t lower your coolant level very quickly they can be messy and make the ventilation system in your car dirty and smell awful.

Heater core replacement can be broken down into a few difficult steps:

Heater Core Replacement

  1. Drain your cooling system
  2. Remove the heater core hoses
  3. Remove your dashboard
  4. Replace the heater core
  5. Reassemble and refill your cooling system

Drain your cooling system

You have to start by draining your cooling system so you can safely remove your heater core hoses without making a mess.  Since your heater core is high in the system you often only have to drain ⅓ to ½ of the system volume to empty the heater core.  

Remove the heater core hoses

The coolant hoses that carry water to and from your heater core will often connect to your water pump, a cooling system manifold or the cylinder head back by the firewall.  These hoses are usually about 1” in diameter and will be the only coolant hoses that pass through the firewall. These hoses may have simple clamps securing them to the heater core or they may have special fittings that require a unique tool to disconnect.

Remove your dashboard

This is the part of the heater core replacement that adds all the cost at your local mechanic.  Your heater core is tucked away in your ventilation system which sits behind your dashboard. In most vehicles, the dashboard has to be removed or at least slid back from the windshield a foot or so to gain access to the heater core.  

Replace the heater core

Once you have access to the heater core you may have to loosen some of the ventilation box mounts to have enough room to sneak the inlet and outlet pipes through the firewall, or those pipes may detach from the heater core entirely.  Be careful when installing the new heater core to avoid damaging any of the cooling fins.

Reassemble and refill your cooling system

Once you’ve got your new core in, it’s time for reassembly!  It is wise to try connecting the new heater core and refilling the cooling system to check for leaks before you reinstall the dash to save some time if you’ve made a mistake or need to make any adjustments.

If this whole procedure seems daunting, you’re right!  Many dashboards have suffered cracks or creases during heater core replacements.  Also, new cars may have airbags that need to be moved to be careful and make sure you’ve got a good repair manual if you attempt this job yourself.  If you need a quick for your leaking heater core, consider using BlueDevil Pour-N-Go to seal the leak in your heater core rather than going through all that work.  BlueDevil Pour-N-Go can seal the leak in your heater core saving you time and money!

You can find BlueDevil Pour N Go Head Gasket Sealer at any of our partnering local auto parts stores like:

  • AutoZone
  • Advance Auto Parts
  • Bennett Auto Supply
  • CarQuest Auto Parts
  • NAPA Auto Parts
  • O’Reilly Auto Parts
  • Pep Boys
  • Fast Track
  • Bumper to Bumper Auto Parts Specialists
  • S&E Quick Lube Distributor
  • DYK Automotive
  • Fisher Auto Parts stores
  • Auto Plus Auto Parts stores
  • Hovis Auto & Truck Supply stores
  • Salvo Auto Parts
  • Advantage Auto Stores
  • Genuine Auto Parts stores
  • Bond Auto Parts stores
  • Tidewater Fleet Supply
  • Bumper to Bumper Auto Parts
  • Any Part Auto Parts
  • Consumer Auto Parts

Pictures Provided By:
heater_core_replacement.jpg – By Chiewr – Licensed by Getty Images – Original Link

8 responses to "Heater Core Replacement"


  1. DALE on October 24, 2019 at 9:04 am

    will blue devil clog a heater core up or coat the tubes and reduce the flow?

    • BlueDevil Pro on October 24, 2019 at 10:07 am


      The BlueDevil Head Gasket Sealer does not contain any solid or particulate matter, so it is a non-clogging product. Specifically, the product is attracted to air flow, so it won’t just go in and coat the whole system. It is specifically attracted to where there is a leak.

      Thank you!


  2. Jaime on October 11, 2020 at 9:38 pm

    What could happen if blue devil is applied through the resivoir instead of the radiator?

    • BlueDevil Pro on October 12, 2020 at 8:26 am


      The product will not enter the cooling system quickly enough. The reservoir does not circulate continuously. By the time it started pulling from the reservoir the engine would already have produced heat. The product reacts around 150 degrees Fahrenheit, so this means the product could start reacting before it was able to circulate and the chance of BlueDevil working would be greatly decreased.

      Thank you!


  3. Tony on December 29, 2020 at 10:00 am

    So you just pour blue devil in through the regular radiator do you pour it while car is on or off

    • BlueDevil Pro on December 29, 2020 at 12:10 pm


      When the engine is cold, you would start the vehicle, put the heater on and blower to the max and then slowly pour the product in through the radiator cap. Put the cap back on and let the vehicle sit there and idle for 50 minutes.

      Thank you!


  4. K on January 17, 2021 at 12:54 pm

    Will it still work in radiator if your heater doesn’t heat but still comes on

    • BlueDevil Pro on January 18, 2021 at 8:22 am


      The motive behind putting the heater on, in regards to using BlueDevil, is to draw heat from the engine to help it from overheating during the 50 minute idle. As long as the engine isn’t overheating, the product would still be able to seal.

      Thank you!


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