HiOutput.com - Thirdgen Heater Core Replacement

Thirdgen Heater Core Replacement

Hopefully this article will make the task of replacing a leaky heater core a bit easier for you all. It's nowhere near the job some people claim it to be, and actually seeing how things fit together is usually the biggest obstacle in the procedure. It's easy enough to tell someone to 'take this off' or, 'look for the screw on top' but having pictures to reference makes it a lot easier for the do-it-yourselfer. These procedures are for a non-AC Thirdgen; one equipped with AC should be similar enough to follow.

You will need:

Wrench to disconnect the battery
Drain pan for coolant
Appropriate wrench or pliers to remove hose clamps on the core nipples
7mm socket (¼" drive preferred) with handle and extension - ratchet may be helpful
Patience (lots)
Trouble light
Replacement heater core (obviously, or you wouldn't be doing this :P)

Underhood

Disconnect the battery ground cable and drain out some coolant.
Remove the two hoses going to the heater core.

Inside

Set HVAC controls to windshield defrost and the temperature control to hot.
Remove the hush panel above the passenger side footwell. Three 7mm screws should do that.
It's best to lay in on the floor on your left shoulder to work.
Looking up, you will see something like this (The dash and the rest of car have been removed for clarity):

Remove four 7mm screws shown below and remove the cover:

You'll see a metal plate; remove two 7mm screws as shown below and slide the plate out to the right - don't throw it too far, as you'll need it when re-assembling the unit.

Avoid touching the foam on the control doors - it's likely gotten quite brittle over the years and will come off in clumps if disturbed.
Remove four more 7mm screws from the piece (picture below) which the metal plate was attached to. Two are in plain sight - if not grab your trouble light ;), the other two are inside the cavity behind where the metal plate was - this is where the extension comes in handy.

Grab your patience. An extra set of hands might help as well.
Pull straight back on that piece of plastic from which the last four 7mm screws were removed; it might help to have someone push on the heater core nipples (heh heh) from the engine compartment.
As soon as the heater core pipes pass through the firewall, tip the front of the core and plastic piece up to prevent the water/coolant from spilling inside your car. If your heater core has been leaking, it's probably not a big deal if a bit more leaks out :(
Take that piece to your work area and swap the new core into place - it's pretty straight-forward. No, I didn't take a pic of it.

Reinstallation

Clean any spilled/leaked coolant from the inside of the heater core cavity - the coolant will not evaporate.
Grab your patience again. And your new heater core assembly.
Assume the position. In the passenger footwell, that is.
Carefully feed the new core assembly back into the cavity in the duct housing - take your time, as you don't want to damage the new core (do you?).
Once the pipes from the core pass through the firewall, wiggle the assembly into place and install the four 7mm screws you removed earlier. They are all coarse threaded - it doesn't matter which ones go where.
Replace the metal plate by sliding it into position behind the flap door. It goes in at a slight angle forward toward the driver's side, and re-install the two 7mm screws to hold it in place.
Replace the cover and four 7mm screws over the whole deal.
Re-install the hush panel.
Remove the hush panel to remove your trouble light(doh!), then re-re-install the hush panel.
Underhood, re-attach the heater hoses and clamps - don't forget to tighten them.
Refill the coolant; re-attach the battery cable and bleed the system of air by your preferred method.
Don't forget to clean your carpet of the spilled coolant.
Enjoy your heat again, and be happy that your windshield doesn't fog up anymore.