How to Replace the Heater Core in Cars

by Contributing Writer; Updated June 12, 2017

Your Buick car vehicle has a heater core under the dashboard that heats up the air from the air conditioning unit before it is sent out by the blower. A faulty heater core can be a huge problem since it can cause coolant to leak out onto the passenger's side of the interior compartment or even cause white smoke to billow out of the Buick car air vents. Thankfully, replacing the heater core is fairly straightforward, although it will take more than one hour to complete.

Under The Hood:

 How to Replace the Heater Core in a Nissan Altima

Removal

Make sure the Nissan Altima's front wheels are in the straight-ahead position. With the ignition off, disconnect both battery cables, starting with the negative. Wait at least 10 minutes for the air bag's energy to deplete before continuing.

Detach the driver side air bag and steering wheel. Disconnect the air bag module connector and horn electrical connector from inside the wheel's lids. Use a T150 wrench to remove the bolts Store the air bag module face up.

Take out the passenger side air bag. Remove the glove box to reach the module connector.

Jack up the Nissan Altima and securely place it on jack stands. Place a clean container directly underneath the drain plug located on the bottom of the radiator on the passenger side. Carefully remove the drain plug and drain the engine coolant from the cooling system. Put the drain plug back in place and set the coolant aside.

Discharge air conditioner refrigerant. If your car used R-12 refrigerant, it's against the law for you to discharge or recharge the system unless you're an EPA-certified technician, so you may need a professional to do this part. Disconnect the heater hoses from the heater core tubes from within the engine compartment.

Remove the instrument panel from the car. Remove the lower panels first starting on the driver side. Removal includes all the screws and connectors, the audio/deck pocket, switch panel, center console, grilles, pillar garnish, instrument stay and steering member. You may need assistance taking the panel out.

Disconnect the air conditioning housing by taking off the refrigerant lines and thermo control amp. Remove the heater unit from the car and the heater core from the unit.

Installation

Install the replacement heater core to the heater unit. Replace the heater unit and air conditioning housing within the car, reconnecting all the lines.

Reinstall the instrument panel, including the steering member, instrument stay assembly, pillar garnish, grilles, center console, switch panel and audio/deck pocket.

Reconnect the heater hoses to the tubes. Connect the steering wheel, both airbags and the glove box back onto the car.

Fill the cooling system. Use new coolant, if you're not certain the old liquid is still good. Recharge the air conditioning refrigerant (unless it requires an EPA-certified technician). Reconnect both battery cables, starting with the positive one.

Run the Altima's engine to its normal operating temperature. Check the climate control operation and inspect the system for leaks.

Items you will need

  • Replacament heater core

  • Jack and jack stands

  • T150 wrench

  • Screwdriver

  • Clean Container

  • Coolant

  • Refrigerant

 How to Replace the Heater Core in a Lincoln Navigator

Removing the Old Core

Drain and recover the refrigerant from the cooling system. The system must be cool and the engine off to avoid injury.

Remove the quarter trim panel on the right hand side. Detach the upper air duct on the auxiliary housing and remove the auxiliary line bracket.

Clamp off and then disconnect the heater hoses. Disconnect the drain hose, blower motor and the electrical connectors for the blower motor resistor electrical actuator.

Remove the auxiliary climate control housing and the access cover to the evaporator/heater core. You can now remove the heater core.

Installing the New Core

Install the replacement heater core into the Navigator and replace the access cover and climate control housing. Reconnect all hoses and electrical connectors, using new O-ring seals where they are needed.

Clean and lubricate the coolant hoses if necessary, using plain water. Lubricate the refrigerant system with clean PAG oil.

Connect the auxiliary line bracket and the upper air duct. Reconnect the quarter trim panel.

Refill the engine coolant level. Test the refrigerant system for leaks with a refrigerant leak detector. Evacuate the system of air and charge it with an R-134a Service Center.

Items you will need

  • Replacement heater core

  • Wrench

  • Screwdriver

  • Clamp tools

  • O-ring seals

  • Water

  • PAG oil

  • R-134a Service Center

 How to Replace the Heater Core in a Honda Accord

Unclamp the Honda Accord's negative battery cable and wait 3 minutes for the air bag system to run out of energy.

Discharge the air conditioning system by disconnecting the suction and the receiver lines from the evaporator core. Drain the coolant from the system by placing a pan underneath the drain plug at the bottom of the radiator and opening the plug to empty the coolant.

Raise the hood and open the cable clamp. Disconnect the heater control cable and turn the valve to the fully opened position. Remove the heater hoses from the core assembly and take off the mounting nut from the heater unit.

Remove the center console from the interior. This includes the gear shift knob (if you have a manual transmission), heat switch connectors (if you have heated seats), front power accessory connector, console mat and rear accessory electrical connector.

Detach the lower dashboard covers, center pocket assembly and glovebox. Also, take off the driver's side under cover panel on newer models of the Honda Accord.

Separate the steering column from the dashboard. Remove the air bag assembly first and make sure the column is in the full up position during removal. Hold the slider shaft onto the column with a piece of wire during removal.

Have another person help you remove the dashboard assembly. You must disconnect the center lower covers on both sides, the SRS control unit and all connectors, hoses and harness that will interfere with the dashboard removal.

Disconnect all connectors to the air mix control motor, evaporator temperature sensor, power transistor and recirculation control motor. Remove the wire harness, heater ducts and blower-heater unit. Loosen the heater core cover and remove the heater core.

Install the new heater core in place. Reconnect everything in reverse order of removal. Refill the coolant and test the system at normal operating temperatures, checking for leaks.

Items you will need

  • Wrenches

  • Screwdriver

  • Drain pan

  • Replacement heater core

  • Coolant

 How to Change the Heater Core in a Buick

Lift up your Buick's hood and disconnect its battery with a socket wrench.

Open the passenger-side door and remove the four screws from the kick panel underneath the glove box.

Remove the kick panel from the vehicle. Disconnect the two wiring connectors revealed by taking off the kick panel.

Open the glove box and remove its contents. Remove the screws securing the glove box to the dashboard and remove the glove box.

Pull down the flange to access the heater core. Remove the two bolts from the heater core case and lift off the case.

Disconnect the heater core's wiring connector. Remove its four securing screws with a Phillips screwdriver and remove the heater core from the vehicle.

Place a new heater core into the vehicle and reconnect the wiring connector. Reinstall the screws. Reattach the heater core case and install the bolts.

Reattach the kick panel and glove box and their screws. Reconnect the battery and close the Buick's hood.

Items you will need

  • Socket wrench

  • Phillips screwdriver

 How to Replace the Heater Core in an Oldsmobile Alero

Disconnect the negative cable from the Oldsmobile Alero's battery. While the car is securely raised on jack stands, drain the engine coolant into a clean container. Most models don't have a drain plug on the bottom of the radiator, so you must take off the lower radiator hose to drain the system.

Remove the drain tube from the heater's housing and disconnect the heater hoses from the core. Take off the center console, if one is equipped. Then, take off the sound insulators on both sides of the car, the steering column's opening filler, the air outlet duct and the floor air outlet to reach the heater core.

Disconnect the heater core cover. Remove the core-to-housing mounting clamps and remove the heater core.

Install the replacement heater core. Connect the mounting clamps and replace the core cover.

Replace the rear floor air outlet, air outlet duct, steering column opening filler, sound insulators and center console (if equipped). Reattach the heater hoses to the core and the drain tube to the housing.

Fill the cooling system, using new coolant if the old liquid doesn't appear clean. Be sure the lower radiator hose is securely back in place before filling the radiator. Reconnect the negative battery cable.

Start up the Oldsmobile Alero's engine and let it run until it reaches normal operating temperature. Observe the climate control operation and check for any leaks in the system.

Items you will need

  • Replacement heater core

  • Jack and jack stands

  • Wrench

  • Screwdriver

  • Clean container

  • Coolant (optional)

 How to Replace the Heater Core in a Pontiac Grand Prix

Remove the Old Core

Unplug the cable from the negative battery terminal. Drain the coolant from the cooling system (make sure you use a clean container for it, if the coolant can be reused).

Remove the air cleaner and duct assembly if the Grand Prix has a 3.1L engine. Remove the fuel injector sight shield if it has a 3.8L engine.

Disconnect the lower floor console and both instrument panel insulators. Take off the outlet cover and core cover, and then remove and discard the core seals and outer seal. Unscrew the line clamp screw, retaining clamp and pipe retainer clamp screw.

Detach the heater core from the lower core case. Extract and discard all the seals (upper, lower, center and side) from the case.

Install the New Core

Attach new heater core seals to the lower heater core case, and then seat the replacement core to the case.

Reattach the pipe retainer clamp screw, retaining clamp and heater core's line clamp screw. Put on a new outer seal and core seals before connecting the heater core cover.

Install both instrument panel insulators and the lower floor console. Replace the fuel injector sight shield or air cleaner and duct assembly--whichever one you removed.

Fill the cooling system. Use fresh coolant, if you're not certain you can reuse the old stuff. Reattach the battery's negative cable.

Start the Pontiac Grand Prix's engine and let it run to normal operating temperature. Check the car's climate control operation and make sure there aren't any leaks.

Items you will need

  • Replacement heater core

  • Replacement core seals

  • Screwdriver

  • Coolant

 How to Replace the Heater Core in a VW Jetta

Removing the Old Core

Unplug the Jetta's negative battery cable, making sure you have the radio's anti-theft codes to enter afterwards.

Take out the facing wall in the plenum chamber and place appropriate drip trays under the engine. Use hose clamps on the coolant hoses and disconnect the hoses from the heater core.

Drain the engine coolant carefully from the system. With a clean container under the core's lower connection, connect a piece of hose to the upper connection and blow coolant from the core into the container with a compressed air gun.

Disconnect the connection flange bolt linking the heater core connections so the coolant pipes can move.

Remove the trim and air vent from the driver side footwell, then remove the heater core trim. With strong foil and absorbent paper below the heater core, open the hose clamps and disconnect the coolant pipes, then remove the heater core.

Installing the New Core

Push the new heater core into the heating/ventilation unit.

Insert sealing rings coated with coolant into the connections on heater core. Connect the coolant pipes to the core, tighten the hose clamps (about 1.5 foot pounds on newer models) and reapply the bolt to the connection flange.

Reconnect all other hoses and replace the engine coolant in the system. Look for any leaks in the coolant circuit for leaks, especially between the coolant hoses and heater core.

Connect the negative battery cable, then evacuate, charge and leak test the air conditioner. Let the Jetta's engine run to normal operating temperatures, then observe the climate control operation and double-check for leaks.

Items you will need

  • Replacement heater core

  • Hose clamps

  • Hose

  • Compressed air gun

  • Wrench

  • Screwdriver

  • Sealing rings

  • Engine coolant

 How to Replace the Heater Core in a VW Beetle

Removal

Disconnect the VW Beetle's negative battery cable. Jack up the car and drain the engine coolant from the cooling system by placing a container underneath the radiator directly below the drain plug. Remove the plug with a crescent wrench, allow all the coolant to drain, replace the plug and properly dispose of the used fluid.

Remove the driver's side air bag. With the steering column in its lowest position, turn the wheel 90 degrees in each direction and twist a 7-inch screwdriver counterclockwise in the hub hole to release each air bag clip. Remove the bag with the wheel turned straight ahead.

Disconnect the steering wheel. With the tires facing straight ahead, disconnect the horn's electrical connector and remove the wheel-to-steering column bolt to remove the wheel.

Detach and remove the instrument panel. Start by removing the screws and connectors on the driver's side, including the steering column. Disconnect all side covers, the glove box, the radio and all electrical connectors. You'll need two people to remove the panel at the end.

Loosen the crossmember-to-chassis bolts from the instrument panel and lift up the crossmember. Disconnect the heater hoses from the core.

Take the heater core out of the heater/ventilation or air conditioning housing assembly. On a ventilation assembly, partially remove the assembly and the retainer clips. On an AC system, discharge the refrigerant, disconnect the refrigerant lines and remove the ventilation ducts.

Installation

Install the new heater core to the heater/air conditioning or ventilation housing assembly. Connect the assembly back into the VW Beetle, reconnecting the refrigerant lines (if they were disconnected and if it is safe to do so yourself) and heater hoses.

Lower the crossmember and re-install the crossmember-to-chassis bolts for the instrument panel. Put the instrument panel back on (this may require an assistant).

Reinstall the steering wheel to the steering column and the air bag to the wheel.

Refill the cooling system and reconnect the negative battery cable. Evacuate, charge and leak test the air conditioner's refrigerant. (If your Beetle is equiped with R-12 refrigerant, then you can't complete this step yourself, and you'll need to take it to an EPA-certified technician.)

Start and operate the VW Beetle's engine to its normal operating temperature. Check the climate control operation and look for any leaks in the system.

Items you will need

  • Replacement heater core

  • Jack and jack stands

  • Wrench

  • Screwdriver

  • Clean container

  • Coolant (optional)

 How to Replace the Heater Core in a Mitsubishi Eclipse

Make sure the Eclipse's tires are facing straight forward. Disconnect the cable from the negative battery terminal and wait a minute. Drain the engine cooling system and discharge the air conditioning system.

Take out the center console box and lid assemblies, along with the nearby switches and the gear shift assembly. Remove the front and rear consoles, driver's air bag, steering wheel and steering assemblies.

Disassemble and remove the instrument panel. Remove the front pillar trim panel, side cover, fog lamp switch, hood release handle, meter bezel, center panel, center air outlet, radio, heater control, center hood, Multi-center display, center speaker, glove box and passenger's air bag.

Disconnect the instrument panel reinforcements, knee absorbers. auto-cruise control immobilizer control units, joint duct and strut tower bar assembly.

Remove the air intake hose, air conditioning pipe connection, expansion valve, heater hose and thermistor sensor. Remove the evaporator, automatic compressor controller and water shut motor, and you can now remove the heater core.

Install the replacement heater core. Replace all consoles, hoses, assemblies panels and columns in the reverse order of removal.

Refill the cooling system, using new coolant if the old coolant doesn't appear to be of good quality. Recharge the air conditioning system as well.

Items you will need

  • Replacement heater core

  • Wrench

  • Screwdriver

  • Engine coolant

 How to Replace the Heater Core in a Cadillac Escalade

Open the coolant drain in the bottom of your Cadillac Escalade's radiator and drain the antifreeze mixture into a clean container for reuse. Make sure the container has a tight-fitting cover; close it and set it aside for reuse.

Disconnect the negative battery cable and isolate them. Then remove or disconnect the heater hoses from the heater core, the instrumental panel storage compartment, the center floor air-distribution duct and the hinge pillar trim kick panels. You will also need to disconnect any electrical connectors that may get in your way in this and following steps.

Unscrew and remove the blower motor cover, then remove the mounting screws holding the blower motor in place and remove the blower motor too. Disconnect and remove the steering wheel and column. Undo the instrument panel fasteners and pull the instrument panel back far enough to access the heater assembly.

Remove the screw located on the interior side near the evaporator pipe if it's present. Stabilize the heater assembly against the firewall as you carry this step out, then, working from the engine compartment, remove the four heater assembly-to-chassis screws and the two heater assembly-to-chassis nuts. Remove the seven screws holding the heater cover in place and take the cover out, then remove the heater core from the assembly.

Connect the new heater core to the heater assembly, then replace the cover and screw it into place (seven screws.) Reinstall the four heater assembly-to-chassis screws and the two heater assembly-to-chassis nuts. Proper torque for the screws is 17 inch-lbs, for the nuts 25 inch pounds. Also replace the screw on the interior side near the evaporator pipe, and torque to 97 inch pounds if it was removed.

Reinstall the instrument panel and fasteners, then the steering column and steering wheel. Working in the engine compartment, screw the blower motor and its cover back into place. Back inside the vehicle body; reinstall the hinge pillar trim kick panels and the center floor air-distribution duct. Reconnect any electrical connectors that were disconnected to clear obstructions in the previous steps.

Replace the instrument panel storage compartment, reconnect the heater hoses to the heater core, and reconnect the negative battery cable. Refill the engine cooling system and run the engine up to normal operating temperature. Check for antifreeze leaks and check to be certain the climate control systems are putting out heat when the engine is at normal operating temperature.

Items you will need

  • Clean, covered container for coolant

  • Wrench set

  • Screwdriver

 How to Replace the Heater Core in a Saturn Vue

Removing the Old Core

Disable the Vue's air bag system and disconnect the negative battery cable. Drain and recover the engine coolant and air conditioner refrigerant.

Disconnect the suction line and thermistor connection from the Thermal Expansion Valve. And the outlet and inlet hoses from the heater core. Remove the right and left end panels to the instrument panel and the door jamb switch electrical connections.

Place the gear shift in "Neutral," then remove its horse shoe bezel to access and disengage the electrical connections.

Disconnect or remove everything connected to the instrument panel, especially on the passenger side. This includes the glove box, radio, passenger air bag, all ducts, switches, bracket and retainer connections, the Brake Control Module and Data Link Controller. Remove the panel retainer last.

Remove the heater duct, heater core cover, core pipe cover and pipe foam seal. Remove the heater core by grabbing it at the end tanks.

Installing the New Core

Install the replacement heater core and reconnect the pipe seal, core cover and heater duct. Spray soapy water on the dash seal and core pipe openings to help installation.

Replace and reinstall all connections and components of the instrument panel. Make sure you center the temperature knob and align the air temperature cable lug with the detent spring point. Use a new seal washer when connecting the suction line to the Thermal Expansion Valve.

Refill the cooling and air conditioning systems. Recharge the refrigerant with an R-134a tool. Reconnect the negative battery cable and enable the air bag system.

Items you will need

  • Replacement heater core

  • Wrench

  • Screwdriver

  • Clean container

  • R-134a service tool

 How to Replace the Heater Core in a Mercury Cougar

Removing the Old Core

Disconnect the Mercury Cougar's negative battery cable. Remove the center console from the interior. Disarm the car's air bag system and remove the bag's diagnostic monitor and bracket.

Take the heater outlet floor duct out of the car. Remove the screw holding the air transfer duct and push it into the outlet duct. Unscrew the screws retaining the outlet duct to the heater core cover and release the retaining tabs on each side to remove the duct.

Raise and support the Mercury Cougar, using multiple jackstands. Drain the engine coolant by removing the drain plug on the bottom of the radiator. Replace the drain plug after all the liquid flows into a clean container and disconnect the heater hoses from the core.

Withdraw the black vacuum supply hose from the vacuum source (you can now lower the vehicle). Disconnect the same hose from the air conditioner's vacuum reservoir tank.

Detach the heater core cover that holds the core by releasing the retaining tabs and removing the clips. Remove the dash panel seal, vacuum hose and heater core bracket from the cover.

Remove the heater core from the cover and the case seal from the core.

Installing the New Core

Install the replacement heater core into the cover with the case seal connected. Connect the heater core bracket, dash panel seal and vacuum hose onto the cover. Install the core cover into its compartment.

Put the vacuum supply hose back on to the air conditioner's vacuum reservoir tank by first raising the car once more. Connect the hose to the vacuum source in the engine compartment. Reconnect the heater hoses onto the core before lowering the vehicle.

Reinstall the heater outlet floor duct and connect it to the heater core cover. Reset and secure the transfer duct from the outlet floor duct.

Connect the air bag diagnostic monitor and bracket, along with the center console. Reconnect the negative battery cable and refill the cooling system with fresh coolant.

Start the Mercury Cougar and run it until it reaches the normal operating temperature. Check to make sure the repair was successful and there aren't any leaks in the system.

Items you will need

  • Replacement heater core

  • Jack and jack stands

  • Wrench

  • Screwdriver

  • Clean container

  • Coolant

 How to Replace the Heater Core in a Nissan Maxima

Older Models

Shut off power to the Maxima, especially the air bag system. Disconnect the negative battery terminal and wait at least 3 minutes for the air bag to lose energy.

Drain the engine coolant from the cooling system. Use a clean container if you plan on reusing the coolant.

Disconnect the heater hoses from the heater unit inside the engine compartment. Remove the blower and cooling unit from the interior and then the steering member assembly. Remove the heater unit and the core from the unit.

Install the new core into the heater unit and reconnect the unit in the car. Connect the steering member, cooling unit and heater hoses.

Refill the cooling system and connect the battery cable.

Newer Models

Unplug the negative battery terminal. Wait 3 minutes for the air bag system to lose power. Drain the engine coolant into a clean container.

Disengage the air bags from both sides of the car. Remove driver's bag by removing the steering wheel's lower and side lids and the Torx bolts from the wheel sides. Disconnect the passenger bag electrical connector from inside the glove box.

Disassemble the instrument panel. Remove all components and screws from the panel, then have an assistant help lift and remove the panel itself.

Disconnect the following heater, defroster and ventilation ducts on the rear and sides. Remove the heater housing and the heater core from the housing.

Reinstall the heater housing with the new core installed. Replace all ducts, the instrument panel and the air bags.

Fill the cooling system and reconnect the battery cable. Let the Maxima's engine run to its regular operating temperature. Look over the climate control operation and check for any leaks in the system.

Items you will need

  • Replacement heater core

  • Wrench

  • Screwdriver

 How to Replace the Heater Core on a 1998 Grand Cherokee

Apply parking brake and chock the wheels to keep the vehicle stabilized while you work. This can be done by placing a block of wood behind the tires to keep them from rolling.

Disconnect the ground wire from the battery with pliers or wrench. Discharge the air conditioner.

Place large container under radiator to catch the coolant. Remove the plug to drain the radiator with a socket or wrench. Loosen the radiator cap for a more even flow.

Replace the radiator drain plug and cap and move the container to underneath the engine block. Drain coolant from engine block by removing the drain plug with a socket or wrench. Replace drain plug. It may be necessary to remove and drain the coolant reservoir as well.

Loosen the clamps on the heater hoses with the flat-head screwdriver.

Remove the dash or instrument panel with a Phillips screwdriver; then open and remove the glove box. On the left side behind the glove box are the remaining screws for the instrument panel. Finish removing instrument panel and disconnect all of its electrical parts. Remove the panel from the vehicle for more working room. This may take two people. Lower the steering column into the front seat for support.

Pull the carpet back in the center of the vehicle under the dash until you can get to the bolts on the panel brace. Remove those bolts to loosen the console and remove the console. At this point, it is likely necessary to remove the radio as well by disconnecting the wiring from the rear of the device and loosening the screws on the front.

Disconnect the heater and A/C vacuum lines by loosening the clamps. Disconnect electrical wiring from the A/C unit. Disconnect the computer from the firewall, but do not disconnect the 60-pin connector.

Remove the heater core from the housing using a Phillips screwdriver. Install new heater core and reattach with screwdriver. Reassemble everything in reverse order of how it was removed.

Items you will need

  • Wheel chocks

  • Large sealable container

  • Pliers

  • Wrench

  • Phillips screwdriver

  • Flat screwdriver

  • Socket set

  • New heater core

 How to Replace the Heater Core in a Kia Spectra

Disconnect the cable from the negative battery terminal. Wait at least 10 minutes for the air bag's energy to deplete.

Drain the cooling and air conditioning systems, making sure to recover the refrigerant in a clean container. Remove the heater hoses from the heater unit and the expansion valve from the evaporator core, then plug the lines.

Remove the floor console, A-pillar and cowl side trim, crash pad side covers, hood release handle, dashboard left lower panel, steering wheel and column cover and the cowl cross bar's steering shaft.

Take out the glove box and instrument panel's main mounting bolts. Disconnect the fuse box and radio antenna cable. Remove the cluster and center facia panels, instrument cluster, heater control and radio assemblies, and the dashboard's right lower panel. Remove the crash pad.

Disconnect the heater unit's electrical connectors and remove the upper pipe bracket and side cover. Pull the heater core out of the heater unit, making sure you don't bend the inlet and outlet pipes.

Install the new heater core in the unit and reconnect everything in reverse order.

Refill the cooling and air conditioning systems. Start the Spectra's engine and check for leaks in the system.

Items you will need

  • Replacement heater core

  • Wrench

  • Screwdriver

  • Clean container

  • Engine coolant