Step by step guide on how to replace an automotive heater core, though each car
is different in complexity, these steps outline the basic procedure.
Difficulty Scale: 6 of 10
Tools and Supplies Needed
- Replacement heater core
- Hose clamps
- Fluid catch basin
- Socket set
- Wrench Set
- Screw driver set
- Protective eye wear and clothing
Begin with the vehicle on level ground, engine cold, with the emergency brake on.
- Locate and remove the negative battery
cable, move the cable end far enough away to avoid an accidental connection.
Step 2 - Release the radiator cap (engine cold),
and loosen the radiator drain valve, have a fluid basin ready.
Negative Battery Cable Removal
Step 3 - Some vehicles utilize a common plenum
for both heater core and A/C evaporator core, these types will require the refrigerant
Draining Engine Coolant
from the system, once evacuated, disconnect heater hoses and necessary A/C equipment.
Step 4 - Using the hose clamp removal tool, loosen
and remove the heater hoses from the heater core inlet and outlet fittings.
Step 5 - After the heater hoses have been removed,
locate and remove upper dash mounting screws. Remove any mounting hardware across
the top of the dash assembly, which is usually covered by pop-in trim pieces along
the base of the windshield.
Remove Heater Hoses
Step 6 - Once the upper dashboard mounting screws
have been removed, locate and remove the lower mounting bolts. (Note: Some vehicles
require the center console to be removed to access middle mounting bolts.)
Removing Dash Mounting Screws
Step 7 - Using a small socket or screw driver,
remove mounting screws to gain access to the lower steering column mounting bolts.
Removing Lower Mounting Bolts
Step 8 - On the drivers side of the vehicle you
will need to lower the steering column to allow for the dash to rotate for clearance.
This is done by removing the shift indicator cable (if applicable), then removing
the nuts/bolts that hold the column to the dash assembly. This will allow the column
to become loose from dashboard. In most instances allowing the column to rest on
the drivers seat will supply sufficient room. Locate the dash mounting hardware
on the left side of dash and remove them.
Removing Lower Panel Cover
Step 9 - Once the heater hoses have been removed,
locate and remove the dashboard mounting bolts, knee bolsters and foot shields on
the bottom of the dash assembly, and center console if so equipped to gain access
to the heater plenum. (Note: Some vehicles are designed with access panels
that allow the core to be replaced with minimal disassembly.)
Remove Steering Column Bolts
Step 10 - Slowly pull away from firewall while
keeping an eye out for any wiring or vacuum lines, once back far enough, support
dash assembly in a position that will allow for enough room to remove the heater
Step 11 - Once the necessary obstructions have
been removed, the heater box will be exposed.
- Next, remove and vacuum lines and control
cables from the plenum. Take note on the location of these lines and cables to reassemble
them in their proper locations. (Note: Some models you may need to disconnect the
blower motor wiring and remove the screws from the heater core box to remove the
Step 13 - Locate inner heater plenum mounting bolts
and screw and remove them.
Remove Vacuum Lines
Step 14 - Inside the engine bay, locate the heater
plenum mounting bolts and remove. Remove all mounting hardware holding the plenum
assembly to the firewall, Remove all duct work including windshield duct and air
distribution ducting. This will allow the heater box plenum to become free of the
vehicle which will allow removal of the unit.
Remove Inner Mounting Screws
Step 15 - Once removed, pull back gently on the
plenum assembly while keeping an eye out for anything that was missed such as ductwork,
once its released, remove it from the vehicle. Pay close attention while removing
parts so they can be reinstalled correctly. (Note: There will be coolant leaking
from the heater core, use an old towel to help control spillage.)
Removing Outer Heater Plenum Mounting Bolts
Step 16 - After the heater plenum has been removed,
place plenum assembly on suitable work area for disassembly.
Removing Heater Plenum
Step 17 - The heater core plenum is designed to
fit each vehicle individually so configuration will vary.
Heater Plenum Removed
Step 18 - After the heater plenum has been removed,
locate and remove plenum screws to dissemble to gain access to the heater core.
Heater Plenum Mounting Area
Step 19 - Once all mounting screws have been removed,
gently pull the plenum open to expose the heater core.
Disassemble Heater Plenum
Step 20 - After the heater plenum has been separated,
remove the mounting screws holding the core to the housing.
Disassemble Heater Plenum Box
Step 21 - Then, gently lift the core from the housing
Removing Heater Core Mounting Screws
Step 22 - Once the worn core has been removed,
match the new core to ensure a proper installation, reverse these steps to reassemble.
Install new core in the plenum assembly carefully to avoid damage, reassemble the
plenum accordingly. Clean and inspect the heater box to make sure seals and gaskets
are in good condition and reusable.
Removing Heater Core
Install the new heater core back into the heater box plenum and clamp the new
heater core into place. Reassemble heater plenum and reinstall into vehicle, reinstall
blower motor wiring, screws, vacuum lines and control cables. Carefully, install
the dashboard back into position and re-attach tie bars and mounts. Reinstall any
under dash covers that were removed during dis-assembly. Once the dash is replaced,
attach the heater core hoses under the hood. (Note: Replace heater hoses and clamps
if needed.) Reattach the negative battery terminal, start the engine and adjust
the heater on its highest setting,
New Heater Core
. Allow the engine to reach operating temperature and check
for leaks. (Note: It isn’t uncommon for air to be trapped in the system that will
cause problems such as no heat and engine overheating. If this is the case, many
vehicles have a bleeder valve to allow trapped air to escape from the system which
is usually located near or on the thermostat housing. (Caution: Coolant can be extremely
After completing the job,
the air conditioner
(if needed.) Recheck the system for leaks while testing
the blend door operation, verify all dash functions operate properly.
Use caution when installing the heater core, these units are made of thin metal
and plastic and are easily broken. Use a digital camera/phone to take pictures during
the dis-assembly process, this will aid in reassembly if things get complicated.
The glove box will need to be removed in most cases to allow access. Some plenums
have a small door, others will have to be disassembled to gain access to the heater
The heater core is similar to the radiator located in the vehicle’s
. The blower motor forces air through the core and into the air duct system
allowing temperature controls which enable defrost floor and front vent modes. The
most common cause of heater core problems is neglect, cooling systems need to be
serviced on a regular basis, coolant can become corrosive and will cause deterioration
of the core.
- Always use a quality replacement heater core.
- Check the condition of the heater hoses.
- After disconnecting the battery, allow a minimum of 10 minutes before working
around the air bag system.
- Ensure the roundness of the heater core hose fittings to help provide a
Article first published 2016-02-04