Great pics.

(I'm about to well at some point) flush out the A/C evaporator, replace expansion valve and all seals, so I might as well do the heater matrix while I'm there.

Along with removing the doors windows and tailgate, the dash is the only remaining part of my truck that I have not taken apart.

Massive cleaning opportunity awaits!

I have a lot of good info on this post and I am about to try and do this big job this Coming weekend. I have a new heater core. And a new A/C Kit that includes the compressor, dryer, and expansion valve and a bag of seals. My goal is to Replace the expansion valve, and the heater core while I am in there.

The A/C has been depleted by a shop. And this weekend is go time! But I have a few questions and I cant find a way to start a new post so I'm sorry for using this one.

Any concerns about the airbag going off during removal? Is it safe as long as the battery is disconnected?

Any other parts I should check or replace while I'm in there? I have a 97 4runner 2wd 6 Cyl about 400, 000 miles. Any extra info would be much appreciated!!

Here is my point about the heater core. Try NOT to mess with it if you have good heat. Just flush it many times if you want to.

Getting the ac components out and back on is easy. But, why you want to replace all that? Here is how you check the compressor. Hold the high side by placing your thumb as to make a good seal. Then turn the clutch (not the pulley) by 15 to 20 degrees. Do you feel lots of pressure build up under the thumb and hard to hold? If so your compressor is good. My DD is a toyota sprinter "aka geo prizm" (92) with 265K miles. I use the AC a LOT (west TX is hot) but the AC is ice cold and still the factory gas and parts all around. Make sure you clean the condenser often.

Is there a drain for the heater core if its leaking? I think mine is leaking but theres no spillage or smell in the cabin. Just every time i start the truck after its been sitting i hear what sounds like the heater core filling up with coolant as if it drained empty.

If heatercore is leaking it will drain through the AC drain. How is the coolant level in tha radiator and the reservoir? Do you have to fill it often?

The resivor goes about half down every couple weeks. I can smell it out side the car, but only sometimes see apots on the ground

I’m about 2/3 of the way through replacing my heater core on a 1999 SR5. It appears to be the original unit, which is impressive considering it was 20 years old and had been on there for 396k miles. The original post with all the pictures was phenomenally helpful. I wanted to add a few comments for anyone that may reference this thread in the future:

-take the center console out first. You’ll need the room to move around.
-all you need is a T40, 10mm, 12mm, 14mm, and Phillips screwdriver
-probably goes without saying, but don’t forget to remove the hoses from the heater core in the engine compartment. Also, pull out the rubber grommet to reuse later
-having both front seats out gave me a lot more room to move around
-I was unable to completely remove the metal cross member tube like the OP did. There are far too many wiring harnesses strapped to it and I didn’t feel comfortable moving them all. However I did unbolt it on both ends and pulled it back from the passenger side.
-getting the heater box pulled back and rotated far enough to access the heater core is really challenging with the crossmember in there but it’s possible. Getting the factory one out was easier because the short sections of pipe from the core to the engine bay can be disconnected. However, the replacement unit I bought had the short pipes clamped on and it was therefore a tight fit to slide it into the heater box but I eventually got it. The OP showed removing the airbag module (the three T40 torx screws) and I also removed the ABS module to give me a little more room.
-I have the manual A/C controls and i did not remove the climate control unit. I did however unhook the cables for hot/cold and vent/recirculate from where they terminated.
-I laid out a piece of plywood on saw horses and labeled every bolt I took off and noted where it came from. This made reassembly much easier and I didn’t worry about missing anything.
-separating the two halves of the heater box was pretty challenging. Getting them lined up again and back together was even trickier
-there are two metal supports that attach at the trans tunnel. The OP removed the bolts at the tunnel but not at the top. I also removed the top bolts to provide some more room since I didn’t remove the cross member.
-as someone else mentioned, it was a great opportunity to clean all the trim pieces as I went along. The PO was a smoker so there were ashes and grime on everything and I was really able to get things clean.

I still need to get everything buttoned up tomorrow so if I think of anything else, I’ll update this post.

Reviving an old thread....I have coolant puddling in my passenger footwell. I checked the hoses going into the heater core in the engine bay and they are dry. Is this a bad heater core or are there any connections/hoses in the cab that can be replaced?

Thanks
Kristian

Sub'ed for future reference! When it's comes time to do mines.

That’s exactly what was going on with mine. I had a lot of leaking in the footwell and engine bay was dry. My heater core was corroded and leaking into the heater box and into the footwell

Ok thanks. I'll loop around the core for now and get one on the way. Fun times ahead lol.

I'm just here to laugh at the guy who thinks green coolant killed his engine.

Hi, I'm new here (and to car maintenance generally), recently picked up a '96 V6 SR5 with 257K miles. Yesterday I replaced the valve cover gaskets to fix an oil leak and today I started leaking coolant from the passenger side firewall. I just ran it for 5 minutes in the driveway with the AC on and the puddle was significant; pretty disheartening. So my questions for the more knowledgeable and experienced...

1) Before I buy a new heater core and take the whole dashboard off, is there any chance it's something a little simpler like a loose connection?

2) Any way to just get through the glove box to have a look without taking everything apart?

3) Did I screw something up during the gasket job or is this just a bad coincidence?

Are you sure it is actually coolant that is leaking? Passenger side firewall is where the AC drain line comes out and it just drips to the ground from there.

Now I'm embarrassed, I think maybe it is condensation. I just put a paper towel under the leak and let it run for a few minutes. No greenish color on the paper towel at all. I left this out of my first post for brevity but I took it to get inspected this morning after finishing my gasket job, but it didn't pass for unrelated reasons (steering rack bushings, lower ball joint, front brake lines - I have more fun ahead) but the mechanic mentioned I had a pretty bad coolant leak, which was news to me. I assumed he knew better than I would, so I believed him.

Can I test the heater core by idling the car and running the heat? This would not create condensation but would cause the core to leak if it had one, yes?