Ok, so the first thing to do is remove the one heater core box bolt that is under the dash on the passanger side behind the carpet and cut the two black taps with a dremmal on eithe sided of that bolt. Next remove all the undash plastic, glove box, front dash cover and insterment cluster. Next on the driversside there are two 90deg angel brackets under the stearing colum remove them (4 screws) also there are two screws on the lower part of the dash one one each side near the floor next to the door that need to be removed. After that you need to remove the speaker covers and the defrost vent cover to access the screws that will lossen the dash I think there are 6 screws. Once they are removed the dash will roll back. You need to disconnect all the wire harneses that are connecting the dash to the fire wall so the dash can be pulled out farther. (I found that tilting the dash just did not work there was not enough room to work.)

Ok time to remove the heater core in the engine compartment there are two bolts and one nut. The nut is right next to the hoses that go to the heater core. One bolt is just to the left of the distributor below the heater core supply hoses. the other bolt is the hardest bolt to get to it is in the A/C evaporatior box where it says cut here for service so get in there and lossen that bolt and the heater box comes right out on top of the hater box there are two screws that are holding a cover over the hater core remove them and that is the core. To reassemble just do it all again backwards.

The total project time for me was 5 hours. It would have gone alot faster if I had some swivel sockets and longer extensions. I hope this helps you. WHAT EVER YOU DO DO NOT ATTEMPT TO SPLIT THE HEATER BOX THERE ARE SCREWS GOING ALL AROUND THE BOX AND YOU WILL MORE THAN LIKLEY BREAK THE BOX AND AHVE TO REPLACE IT. THERE ARE PEOPLE SAYING TO SPLIT THE BOX ON SOME POSTS BUT THAT DOSENOT WORK ON A 1998 BLAZER.

GOOD LUCK I HOPE THIS HELPS YOU I DID 4 DAYS WORK OF RESEARCH TO FIGURE OUT HOW TO DO THIS REPLACMENT.

I would have loved to see this yesterday since I just started on a 98 blazer heater core replacement about 1 hr before you posted this. It took about 7 hours to get everything apart, replaced and back together. However forgot to plug 1 thing in so have to rip dash apart again. But you had very good info listed there, exactly how i did it.

Excellent, I was wondering how to do this on my 98 2DR 4x4! I got down to the heater box and couldn't figure it out so I reassembled. My core was never visibly leaking however, periodically, I can smell antifreeze shortly after windshield and side windows will fog. Usually happens after strong accelleration. But it goes away eventually. Is it possible to have a tiny leak in the core?

WOW, That was easy. I would have been working on that forever if I didn't find this page.

Now here is a question. Do you have to put any additives in to stop the electrolysis? Since it is a aluminum heater core and iron motor and you have water as a conductor. I think I remember a pill you used to have to put in the Cadillacs. My core went 1 year after a flush with nothing added.

Jonathon's execlent info...

I pulled out what hair I had left this afternoon trying to get that &%$$# box out. I didn't succeed and gave up for the day, besides I was freezing and my hands quit working.

I bought the Hayes manual and it is FLAT out WRONG on removing the heater box. At least I can do this now and attempt to put my 2000 Blazer back together. Thanks for posting the excellent description of removing the heater box.


:biggrin:

Ok, so the first thing to do is remove the one heater core box bolt that is under the dash on the passanger side behind the carpet and cut the two black taps with a dremmal on eithe sided of that bolt. Next remove all the undash plastic, glove box, front dash cover and insterment cluster. Next on the driversside there are two 90deg angel brackets under the stearing colum remove them (4 screws) also there are two screws on the lower part of the dash one one each side near the floor next to the door that need to be removed. After that you need to remove the speaker covers and the defrost vent cover to access the screws that will lossen the dash I think there are 6 screws. Once they are removed the dash will roll back. You need to disconnect all the wire harneses that are connecting the dash to the fire wall so the dash can be pulled out farther. (I found that tilting the dash just did not work there was not enough room to work.)

Ok time to remove the heater core in the engine compartment there are two bolts and one nut. The nut is right next to the hoses that go to the heater core. One bolt is just to the left of the distributor below the heater core supply hoses. the other bolt is the hardest bolt to get to it is in the A/C evaporatior box where it says cut here for service so get in there and lossen that bolt and the heater box comes right out on top of the hater box there are two screws that are holding a cover over the hater core remove them and that is the core. To reassemble just do it all again backwards.

The total project time for me was 5 hours. It would have gone alot faster if I had some swivel sockets and longer extensions. I hope this helps you. WHAT EVER YOU DO DO NOT ATTEMPT TO SPLIT THE HEATER BOX THERE ARE SCREWS GOING ALL AROUND THE BOX AND YOU WILL MORE THAN LIKLEY BREAK THE BOX AND AHVE TO REPLACE IT. THERE ARE PEOPLE SAYING TO SPLIT THE BOX ON SOME POSTS BUT THAT DOSENOT WORK ON A 1998 BLAZER.

GOOD LUCK I HOPE THIS HELPS YOU I DID 4 DAYS WORK OF RESEARCH TO FIGURE OUT HOW TO DO THIS REPLACMENT.

Is this the same as a 99 s 10

Is this the same as a 99 s 10
Yes it is the same as a 99 S10. look at Blazee's new thread, for detailed info.
Southern

Good job! I was gonna do mine myself about a month ago, but my dad said, "Don't try it!" It took my friend and his cousin about 4 hours to get it done. Feels good to have heat, huh?

Thanks for the help. Hayes manual had me with the Dash on the floor looking at the heater box and not knowing how to get it off.

Your steps were bang on. My 99 Blazer is pretty much the same as your 98. The key was the 2 dremel cuts. Without that your lost. Chiltons manual has you removing the fron fender and blower casing etc to get at those 2 bolts from the firewall side

has anyone replaced thev core on a 91 s10 pickup

has anyone replaced thev core on a 91 s10 pickup

There's a good walkthrough here (http://www.sytyarchives.com/howto/viewarticle.php?article_name=heater_core.php&dir=climate_controls).

thanks 98 blazer i just printed out the instructions ready to go

jonathondw,

I got everything apart except for the bolt in the AC evap. How did you get in there? The last bolt is in there. I need to get it out. Cold weather is comming and I need to get this done. I got the Blazer apart in the garage.

OK, after reading about a ton of posts and 2 hours later. I finally found the last bolt and how to get to it. I got the heater core out. Now my question. The old core had some sort of insulation foam around the edge and 3 wires wrapped around it horizontally. My new core doen't have this. Do I need to go get some? is the insulation foam and wires needed?

I was not sure at first where the last bolt was. So I hope this helps.
I cut the “Cut here for service” plastic and then removed the blower resistor (3 screws). I could not get to the last bolt from that opening. I drilled a 3/8” hole 4 ½” down in the A/C evaporator box. I used a 10mm socket with 3” extender in the opening (after I dropped it once I strapped a wire tie to it). I inserted another 6” extender outside through the hole into the 3" extender and went straight in to the bolt. This made things very easy for me. By the way I put a rubber plug back in the hole. I used a ½”plug from ace hardware ($.25) with some RTV to keep it in place.

I'm going to be changing the heater core in my buddies S10 Blazer. It sounds like a PITA but within my abilities. His is a 1995. Is it the same thing pretty much?

Thanks

I thought I'd contribute some pictures. The instructions were great to have for this job. Almost done....

http://i10.photobucket.com/albums/a136/bigdinz/housingremoval.jpg
http://i10.photobucket.com/albums/a136/bigdinz/housingdremelcuts.jpg


If any of you that have done this before can help me out I got a small problem. Maybe one of you know where the connections in the picture below go. They are all the way on the right side and I can't for the life of me remember or figure out where they go.
http://i10.photobucket.com/albums/a136/bigdinz/wires.jpg

I think the connector on the left goes to your air bag. I don't remember what the connector on the right goes to. Maybe it goes to the top of the heater box assembly.

I appreciate the input but I'm positive that all the airbag connections are yellow. I for the life of me do not remember any connections to the heater box. I guess I'll have to undo all that I have put back so I can figure it out. I just do not see anywhere they could go. All the electronics have connections and these 2 look pretty important to me. This really blows, I was hopeing to find the connections while reinstalling everything but I guess not.

I half put everything together to see what problems I may have and of course there are problems.
1. My airbag light is on (I made sure all connections were good).
2. Brake light is on.
3. My defroster/floor doesn't work (only blows through vents).

I am pretty adept at anything mechanical but I cannot figure out where those wires go. I even took the whole dash out again and I still cannot find the connections.

HELP PLEASE!!!!!

I have the schematic for a 99 S10 which should be the same as yours. I don't know if you know how to read a schematic , but I can email it to you. Email me at c_phill@bellsouth.net
Thanks
SC

***UPDATE***
I found where those plugs went. The one on the right goes to the top of the heater box (srbianats..you were right!) The one on the left goes to that junction box on the outside front of the heater box (right in front where it splits). Now with all connections good I am still getting the airbag light and now my dome lights won't go out when all doors are shut. !!!!!Lord help me!

hey , do u know where i can get a diagram to change my 96 blazers heater core...cuz i think our years may be different . not sure..any help from an yone would be appreciated..if you can help my email is blakkrozes@yahoo.com ..


thanks,
"girl in need of heat":banghead:

--UPDATE--

I found all my problems and they were all minor ones (not putting fuzes back in...LOL). Thanks for the help people.

Do you have any suggestions on a 94, I need to replace mine..

Sorry, I got rid of my money pit last year! I will say that my friend changed it out for me for $100, compared to the $1200 the repair shop was going to charge. It took him and his cousin like 4 hours, compared to the 8 the shop quoted me. I guess my advice is, if you can do it yourself or have a mechanic friend do it, it'll save you a lot of money.

Hello - I like most other people have gotten the dash apart and am staring at the black box containing the heater core. It's staring back at me and I think laughing.

I've removed the two bolts in the engine compartment and the nut next to the heater core hoses (engine compartment) but haven't cut into the box that says "for service cut me - then you shall repent and call gm and pay through the nose to find the one hidden bolt"

so... any suggestions? I really don't want to cut up the plastic that says cut me. Where is that last bolt?

Hate to break it to you but it's under that spot. You gotta cut it. I patched the hole with a plastic seal kit from advanced auto. It looks similar to a fiberglass patch but it dries black. Good luck.

nah not at all - hey thanks a lot for the quick reply!

Alright... before I do the cutting - the arrow in your picture (the big arrow) is pointing down near the base of the evaparator box -- but cut here is on top.

Did you cut the top of the box? (or somewhere along the side)

thanks again

nah not at all - hey thanks a lot for the quick reply!

Alright... before I do the cutting - the arrow in your picture (the big arrow) is pointing down near the base of the evaparator box -- but cut here is on top.

Did you cut the top of the box? (or somewhere along the side)

thanks again

i just did this on a '99. it's different, but pretty close. i wouldn't bother cutting at the 'cut here for service' place. that whole housing cover is a soft plastic material, and you can cut it easily enough with a razor knife, but i found it was easier to just undo the cover and move it out of the way. first, remove the 2 10 mm bolts holding the cover on to the firewall (one needs to come out to get the heater core out anyway). disconnect the electrical connector to the blower resistor. there are 6 7/32" bolts holding the 2 pieces of the plastic cover to each other. remove the top 2 and the 2 closest to the front of the car. you'll be able to bend the plastic cover out of the way. then remove the 3 bolts holding the blower resistor in place and remove it. you'll be able to get a 10 mm universal socket on a long extension down into the A/C compartment and remove the last bolt. just be careful not to drop it, although if you did, you'd be able to get it out once you remove the heater box anyway. this is the bolt that the fat arrow is pointing to.

OK, well, like many of you, I too am now in the club. I just finished changing the heater core in my 2000 Olds Bravada.


Have any of you read the book 1984? I never understood toward the end of the book how they broke that man and turned him into one of them. This project has helped me see that. I have submitted to my Bravada. I'm changed. I've stepped through to complete surrender.


OK, so a hot shower and a neck rub will bring me back. Let me get on with throwing in my input.


For starters, I didn't dremel the tabs in the begining. Instead I opted later to use brute force and rip the #$ #@%^#! %&$(#*@ piece of #$*@ heater box off of the firewall. That was of course after removing all the other bolts from the engine compartment.

I didn't cut where it says "Cut here for service", like the post abave mine says, I removed a few extra bolts and folded the soft rubber cover back. I used about a 14 inch extention with a swivel and a 10mm socket to get down inside the little hole in the engine compartment to get the pain in the @55 bolt out. fortunately I have small hands that fit inside there so I could grab the bolt and put it back in upon re-assembly. I have no advice there for you people who can't get your hand down in that hole.

I also didnt undo all of the wiring from the dash. It was a SERIOUS pain the @55, but I didn't want to get into inadvertantly blowing an airbag or some other insanely expensive mistake. It required copious amounts of cussing and stepping back in disbelief that this inannimate object would have the gaul to screw so badly with my world, but with enough wrestling and finagling I was actually able to get the old one out and the new one in. Getting the heater box back in was a chore that would have been made far easier with a second set of hands, but I managed in my restricted state of having only two hands to do the job.

Dash re-assembly was entirely too easy. I still feel as though it was too easy to have been done correctly. The dash seems solid and everything works.


total project time was 4 hours. I couldn't have done it without the first post in this thread. It made little sense before the project, but I printed it and had faith in it. I followed it, deveating only slightly here or there.




Tomorrow I get to replace my balljoints AGAIN for the second time in less than a year. I splurged for the Delco's this time.

Looks like a great page. Thanks for the help guys. I will be doing this to my 2001 2 door Chevy Blazer next weekend, so I can try to add my $0.02 after that. Before I start the project though, does anyone have any more pictures of the project? Such as the hidden bolt location (behind the pastic shroud under the hood)? I'm just interested in as many pictures and details as I can get before I start this painful experience. Also, how many wiring harnesses do I have to unplug? Do i have to touch the passenger airbag at all?

I'm not looking foward to doing this...

Thanks though!!!

Looks like a great page. Thanks for the help guys. I will be doing this to my 2001 2 door Chevy Blazer next weekend, so I can try to add my $0.02 after that. Before I start the project though, does anyone have any more pictures of the project? Such as the hidden bolt location (behind the pastic shroud under the hood)? I'm just interested in as many pictures and details as I can get before I start this painful experience. Also, how many wiring harnesses do I have to unplug? Do i have to touch the passenger airbag at all?

I'm not looking foward to doing this...

Thanks though!!!



I didn't disconnect the wiring harnesses. I didn't fully remove my dash. It would have been a LOT easier to replace the core had I done that, but I had a lot of apprehention about messing with airbag wires, so I toughed my way miserably through removing the old core and installing the new one without removing the dash entirerly.

I don't have more pictures of the project, but if you print the first post in this thread and take a leap of faith into this project you should be able to get through it. Most of the first post made little or no sense, but as I hit problems they were addressed in order in my print out.

I pity you for having this project looming in front of you.

Chadwick

OK, so my dash is off. I've printed the first post in this thread and that helped a lot. I "cut here for service" and got that bolt out (thanks to my small hands). I'm back into the inside of the truck here. There's a large black cover that splits (top piece, bottom piece), then behind that there is the heater core. There also a small cover that snaps into the top split piece (2 clips) on top of the heater core. I've lossened every screw/bolt I can see, and a couple I had to do by feel. I can't get any of these black plastic covers to come completely out. Where all is top piece connected to bottom piece? I undid 7 screws (I counted them just now). I'm yet to see a picture in any manual or post thread that looks like what I'm lookin at. My truck is a 98 Blazer 2Dr, ZR2.

I'm about to resort to the hammer and chisel method here, because I need this thing fixed, and the mechanic wants $700.

What causes the heater core to go out. I've changed the thermastat, radiator, and heater core. A week later the new core starts to leak. Is there a sensor or clogged hose. please help

my '99 Blazer has an aluminum heater and radiator core. if you use the wrong kind of antifreeze, you can corrode the aluminum. but if it started leaking within a few weeks, i'd be surprised if that's the cause. probably just have a loose connection on a hose. or the core itself was defective, which would suck b/c you'd have to redo the entire job to get the core replaced.