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1998 Suburban don't be scared of the rear TXV

1wheeler1 on Tue July 07, 2015 11:47 PM User is offlineView users profile

I'm in the process of rebuilding/repairing the AC in my 1998 Suburban with rear air. After reading through many forum posts I was really worried about trying to access the TXV in the rear for replacement and flushing. Many posts talk about not being able to disconnect the lines under the rear AC that are exposed to the elements and I believe half aluminum and half metal which tends to corrode/bond together. Sound like many lines have been damaged trying to get these apart and even though mine were in great shape I decided not to attempt disconnecting them.

It takes a little work and a few tools but it only took me about an hour or so to access the TXV without disconnecting those lines. The key is having a good selection of 1/4" driver tools like ratchet, hand driver, few different length extensions and swivel joint. I also used one of those 90 degree drill adapters that fit in my hand driver just because I had it but don't think it's needed. A finger ratchet is also nice that you can put a extension on and turn with your fingers.

These are the steps from memory and may not be exact (especially trim removal) but I thought I would post in hopes to help someone else searching.

1. Remove rear 3rd seat.
2. Remove the upper shoulder seatbelt mount behind passenger side second row.
3. Remove the large plastic trim piece that was behind the seatbelt mount goes floor to ceiling (C-Pillar?) . Will require loosening that passenger side sill plate.
4. Open the rear doors and remove the trim piece to the right just inside the door next to rear heater air intake. I have barn doors and this piece had the lock/unlock switch in it.
5. Remove the trim above the heater/ac housing. (my screws were exposed in cup holder and storage tray)
6 Remove the final large heater/ac box cover by removing all screws and un-snapping and tilting towards front of vehicle.

Once all the trim has been removed just the black heater/ac box should be left.
Now you need to remove two nuts from under the vehicle where you can see the ac and heat lines go up into the heater/ac box above. These AC fittings are the ones people have problems taking apart and in between them you should see two studs that hold the heater box down.
On one of mine the stud spun when loosening so I had to use vice grips on the end of the stud to hold it while loosening with an open end wrench.
After you've removed these nuts the heater box above should move around quite a bit.
I then removed all of the wiring retainer nuts and relay mounts from the box, unplugged the wire and moved the wire harness out of the way.
Now the fun begins and you begin removing all of the screws that hold the top and bottom half of the heater housing together.
You're only splitting the rear half and really there are only 2-3 screws that are hard to get to in the back of the housing.
With those studs loose I was able to lift the housing up a bit and then tilt it out putting a block behind it to hold it out.
You do want to be careful to not damage those hoses below and just move it out enough to get you hand behind or under the unit to get to those back screws.
They're not very tight and once loosened can usually be turned by hand with and extension and socket.
After all the screws are out you should be able to get the top of the case off and see the TXV next to the evaporator.
To undo the TXV I did cut a small square opening in the side of the housing so I could get the wrenches on it.
I just drew the square I wanted to cut and then used a hacksaw blade by itself at a shallow angle to cut the plastic taking care to not hit the TXV or lines.
If you've been researching this you've probably read about the GM TSB bulletin that talks about a template to cut a hole. I believe when they are doing it they weren't splitting the case in half to change the TXV and you may not need the hole if you have the right wrenches. If you do cut the whole make sure to seal it up good when done. I was going to use plastic epoxy and duct tape but now thinking maybe just putting the plastic piece back in and cover with Gorilla tape just in case I need to get to it again.

Can't comment on putting it back together yet since still waiting on parts. Back screws will probably be a pain but just takes time.
I'll try and update the post after assembly.

Thanks and good luck.

“I’m so thankful I had a childhood before technology took over”

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