Replace Heater Core

[sdoan]

I replaced the heater core today on my old '83 that is now owned by friends. If you want to do it you should know that the first step is to remove the passenger seat (left hand drive cars) . The good news is that you do not have to remove the crash pad, steering wheel, gauges, windshield or engine though that might be helpful. You should also know that it took me damn near 8 hours. Hope this info saves you a little time.

Remove the passenger seat and remove this bolt.


You can actually do a lot of other things first, but you can't avoid removing the bolt and the silly heater duct.

Remove center console.
Remove glove box.
Remove right side speaker grill.
Remove the glove box crossbar.
Remove the 2 piece black plastic heater duct that joins above the glove box - one screw for each.
Remove the white plastic duct behind the glove box (four bolts). It ducts air from the the fan through the heater core. The heater core is in the black box with the white X on the left.


Remove radio console trim, ashtray, fascia (note screws under dash vents and at the back of the ashtray receptacle) and finally the steel supports either side of the radio. Photo shows right side support removed and lying below radio console.


Remove plastic panel under steering wheel. There are a couple of screws that you must get from below including the one in the picture at the dash light dimmer knob. The knob pulls straight off.


Then remove the duct (one screw) from behind the steering wheel under-panel.

There is a white plastic duct attached to the heater box that is connected to a black connector that directs air to the center dash vents. Below are two pictures of it (top pic shows it upside down, lower pic shows reinstalling the two pieces.) To remove, take out the screw at the base of the white duct, and the screw that connects the mouth of the black duct to the top of the center vent opening. The white duct must be pushed up to disengage the clips on the back of the heater box and then pulled away from the heater box.



Disconnect the black control cables that go to the right side (temp and fresh/recirc) from the levers they control. Disconnect the white defrost/heat/vent cable from the lever on the left side of the heater box. Then remove the 4 screws that hold the cable control panel into the dash. Push the control panel through the dash and to the left so it is out of the way.

Remove kick panels and door sill plates on both sides and peel the carpet back to expose the black plastic ducts that carry air under the front seats.
Remove the bolt that holds the duct (see first photo) and pull them down and away from the heater box.



Go into the engine compartment and drain the coolant. Remove the heater hoses from the heater core then pull the oval rubber grommets out of the firewall so that the inlet and outlet of the heater core are exposed.

Go back into the car and remove the 2 bolts (sides) and 2 nuts (top) that hold the heater box into the car. Pull and twist and it should come out the passenger side. Once out it should look like this. (BTW, don't be tempted to pull the bottom portion off (in my hand in the picture) to get the heater box in or out - it is not necessary and it is impossible to get on or off when the box is under the dash without breaking it).


At this point the bad old leaky, stinky heater core is no longer in your car and you should rejoice!

[sdoan]

A very cool thing about the Tercel heater core is that it just slides in and out of the heater box. It's held in by a single screw and a clip.


I also did a couple things to reduce rattles and make the heater controls work better.

On the side of the heater control box is a very complicated 3 bar lever that controls the heater/defroster/vent doors leaving the heater box (lower left side in the photo above). Lubing the friction points with synthetic grease really helps.

The foam that seals the connections between the pieces of duct-work can be replaced with 3/4" wide, 1/4" thick adhesive weatherstrip. The picture below shows it on the center duct.


There are also thin adhesive strips of felt or some other cloth that insulate the plastic dash panels. I replaced or reinforced these with cloth "friction" tape.

[sdoan]

Reinstalling the whole mess is not too bad.

The first thing is that the heater core has foam padding on the sides and the ends. the photo below shows it bare so it would rattle around if installed like this. It needs adhesive weather strip on both ends and the sides to hold it in place and to keep air from blowing by it. When you pull out the original you will see it. No weather strip in the photo below.



The heater box with new core is the first thing to install, but make sure the bottom section is attached (don't remove it like in photo below), because it is impossible to install later.


The center duct has to go behind the dash in two pieces and be assembled there.


If you've replaced the foam with 1/4" thick weather strip the pieces will be tough to push together but it will work.

[dlb]

this is a deadly write-up! way to go, sdoan.

[ARCHINSTL]

WOW!
Now a Sticky!
Tom M.

[takza]

This is WHY I always try to keep decent coolant in an older car...to avoid this kind of job. And why I don't do chemical flushing.

Looks like the Tercel is easier than my truck was....I literally had to remove the whole dash...only thing left was the steering wheel.

[danzo]

Great write up sdoan, thanks for the info. I had no idea it was so involved. If my heater core busted I think I would just override 'er since I don't need heat 9 months per year.

[sdoan]

Thanks for the props. hope it's helpful.

[Petros]

all heater cores on all cars are like this to reach, some are even worse. You would think they would make access a lot easier. This acutally goes a lot faster once you have done once or twice. If you have air conditioning, this process is much more complicated. I do not know of anyway to change the heater core without removing the a/c evaporator, which means evacuating the system, and recharging it later, adding to the cost and labor.

Good write-up, will make the process seem less intimidating I should think. One good thing about the Tercel, almost all the dash and ducts parts come out with screws or 10mm bolts, no plastic clips to break or replace.

[xirdneh]

where did you get the heater core? and how much?
i have not been able to get anything but aluminum around here

[sdoan]

It was $50 from O'Rielly's which seems like a good deal. They had it one store and just brought it over (not a special order).

[xirdneh]

It was $50 from O'Rielly's which seems like a good deal. They had it one store and just brought it over (not a special order).

thats where i got the last brass one but they had to order it three times before they found one that was not aluminum
that was four years ago
i have not been able to get a brass one since
there must be some on a shelf here and there somewhere

[ARCHINSTL]

O'Reilly's shows it on its web site, also for $50.
It is a Murray, part #399317, and is shown to be of copper/brass.
It does not show any available in the St. Louis area (no surprise), but can be gotten within 2-3 days.
It is shown to fit all Tercels from 1983 through 1990.
Autozone and NAPA show the Spectra brand, which is aluminum, for $50-58. Advance does not show one at all.
Tom M.

[hberdan]

Great Info! I've been putting this repair off for a couple of years. Now I have no excuse!

[takza]

Great Info! I've been putting this repair off for a couple of years. Now I have no excuse!

By the time you've finished you'll wish you had found one?