98 Blazer heater core replacment (I just did it)

[jonathondw]

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.

[jmetzger]

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.

[ss262]

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?

[zx9rwheelie]

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.

[bobpombrio]

Originally Posted by jonathondw

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.

[jedinyte04]

Originally Posted by jonathondw

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

[Southern Comfort]

Originally Posted by jedinyte04

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

[marly87]

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?

[skyzend]

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

[djl462]

has anyone replaced thev core on a 91 s10 pickup

[blazee]

Originally Posted by djl462

has anyone replaced thev core on a 91 s10 pickup

There's a good walkthrough here.

[djl462]

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

[srbianats]

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.

[srbianats]

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?

[Fusefinder]

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.