This was my project today due to the fact that my heater core started leaking in the beginning of the summer and I simply looped it to keep the car going. I have read about this before and people complaining that it's the worst job they've ever done and it takes anywhere from 6-8 hours or even up to 10 hours. The FSM apparently has you removing the dash pad, etc, but I did not use that method. If you go from underneath the dash and remove things in an orderly fashion, you can access the heater core and pull it out.

Be aware that there are no more GM replacement heater cores available. I used an aftermarket replacement from Four Seasons I purchased at Rock Auto.

I used the following tools:
1/4 inch drive ratchet set with miscellaneous extensions and
swivel(s) - this is mandatory. 7mm, 10mm, 14mm sockets
3/8 ratchet with deep well 13 mm socket
Pliers (long handle needle nose are helpful)
Screwdriver




Begin by removing the heater hoses from the heater core in the engine bay. Coolant will spill a bit if you haven't drained the system. If you didn't drain the system, position the hoses as not to leak. I did not have to do this step as my heater core was already bypassed.

Next remove the passenger seat for better access:



Next remove the hush panel. Mine was already off from previous ecm swaps. I believe it's two 7mm bolts and one electrical connector for the light. Once off, you will see this:



Begin systematically removing things step by step (note some pictures might be upside down/backwards due to my position while taking them)

Disconnect the ECM harness and remove the two 10mm bolts (note ECM will drop down):



Disconnect the retaining clip for the blend door motor rod. I used needle nose pliers, but found later you can just pull it off the rod. Be careful not to break it.



Once removed, remove the two 7mm screws holding the motor to the case:



Unscrew the two 7mm screws on the "u" shaped heater duct from the front of the case. You cannot fully remove this piece easily. Remove the accordion duct near the door and pull it out of the way. There is also a tube that goes in to the case. If this falls in it's ok, you can recover it when the case is removed.

Next remove the two 14mm bolts from the metal cross brace. You can see one bolt in this picture:



Once those items are removed, you will have access to the heater core case. There are four 7mm bolts holding it on. The two lower bolts can be easily accessed. I found the best way to get to the top ones was from the outside of the car, kneeling, and using one hand to locate them (very tight space) and the other hand to unscrew them. You might have to use two swivels with the extensions. A flexible extension was also helpful here. Once the screws are removed, wiggle the case out. You can see here where the screw holes are located:



Here is a shot of what you should see once the case is removed:



In the above picture, I had already removed the lower strap that holds the heater core securely in. That has two 7mm bolts on either side. Pull the old heater core out. It is also held in place at the top by this retainer:



Old vs new:



They matched almost perfectly. I did a poor man's pressure test on the new one. Hold your thumb over one end and blow through the other as hard as you can. See if it leaks. There have been reports of new ones leaking out of the box. When I tried to reinstall the new one, I found that the top was shaped slightly different and it wouldn't fit in the retainer correctly and go through the firewall. I had to remove the top retainer clip.

After the heater core is in, reverse the order and replace everything. The screws tend to fall out of the socket, so hold them in place with tape. Once it's all buttoned up under the dash, put body dumdum in the holes where the heater core exits the firewall and reconnect the hoses. Fill the system appropriately and you are done.

This entire process took me 3 hours and 45 minutes including a 15 minute break and 15 minutes of taking the heater core cover back off to recover the stupid tube I dropped through the hole (be careful when reinstalling that tube from the "u" shaped duct to the box). I didn't suffer cut up hands or injuries like some people have.

This job was an exercise in patience, like many jobs on the C4. I think if I did it again I could knock it down to 3 hours. It helps to be flexible and in shape. I climbed in and out the the car from being upside down laying on the floor at least 25 times. If you have a lot of physical problems, this job is not for you. But if you are nimble and adventurous, have at it

Hope this helps anyone in the future.

Matthew

Any questions on the supposed worst job ever on a C4? The dreaded project of all die hard C4 fans?

I was asked by a forum member to repost the pictures after photobucket broke the internet. I uploaded them to flickr. A lot more cumbersome to use, but hopefully these last.

LUCKY YOU JUST HAPPENED TO HAVE THE RIGHT TOOLS, MATTHEW.

Quote:



I can't believe this was five years ago already. Funny thing is I did that job with basic tools that you could buy at the hardware store. Just goes to show you that you don't need Snap On, Mac, and Matco to get the job done. I still prefer them, though

I would rather eat razor blades than do another C4 heater core... ugh...

That is one job I hope I never have to do, but it's good to know it's possible for the little guy to accomplish.

Thanks much for sharing.

I swear, it was the first part put in the car...

Great thread save.

I initially saw this and thought, "Crap, he's having to do that again?" Glad to see it was just a photo-save opportunity.

Yes guys, just a rehash to help another member out. I'd do it again, it's not *that* bad.

hi matatk. will this procedure also work on a 93. let me know thanks rich aka crash

Rich, the dash is totally different on the 93. The location of the heater core is the same but it's a slightly different procedure to get it out. I remember seeing threads about it on other sites in the past. If you can't find them I'll do a quick search.