Heater core replacement instructions please?

Tiny
NICOLE_YOU
  • MEMBER
  • 2000 GMC JIMMY
I need to put a new heater core in my vehicle?
Wednesday, June 24th, 2009 AT 12:59 PM

16 Replies

Tiny
DANNY L
  • MECHANIC
  • 5,648 POSTS
Hello, I'm Danny.

Here is the information you requested. Here is a tutorial to get you started on heater core replacement:

https://www.2carpros.com/articles/replace-heater-core

I've attached picture steps below on heater core replacement for your vehicle. Hope this helps and thanks for using 2CarPros.
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Thursday, February 4th, 2021 AT 10:14 PM
Tiny
MIKE22484
  • MEMBER
  • 1 POST
  • 2000 GMC JIMMY
Heater problem
2000 GMC Jimmy 6 cyl Four Wheel Drive Automatic

How do you seperate the heater box from the firewall. I've removed the hoses, and the one 10mm nut on the ext. Side of firewall and 10mm bolt from bottom of heater box on the inside. The heater box still feels tight. Is there hidden bolts or does the evap. Box on the exterior side have to be removed. Any help would be great. Thanks
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Friday, February 5th, 2021 AT 9:37 AM (Merged)
Tiny
BLUELIGHTNIN6
  • MECHANIC
  • 16,542 POSTS
Removal

Remove the HVAC module-auxiliary.
Remove the screws from heater core cover-auxiliary from the HVAC module-auxiliary.
Remove the heater core cover-auxiliary.
Remove the HVAC module pass thru seal-auxiliary.
Remove the heater core-auxiliary from the HVAC module-auxiliary.

Installation

Install the heater core-auxiliary to the HVAC module-auxiliary.
Install the HVAC module pass thru seal-auxiliary.
Install the heater core access cover-auxiliary to the HVAC module-auxiliary.
Install the screws to the heater core access cover-auxiliary and tighten to 18 inch lbs. (2 Nm).
Install the HVAC module-auxiliary.
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Friday, February 5th, 2021 AT 9:37 AM (Merged)
Tiny
MELINDA627
  • MEMBER
  • 1 POST
  • 2000 GMC JIMMY
  • 4WD
  • AUTOMATIC
  • 202,000 MILES
I am in the middle of a heater core replacement. This is my first time attempting the job on my own. I have taken the entire dashboard apart and am able to see the top portion of the heater core behind the black plastic encasement. My question is, is it necessary for me to remove the bolt from under hood where the back of the dash is located? Another question is, do I have remove the tire in order to get to the other bolts?
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Friday, February 5th, 2021 AT 9:37 AM (Merged)
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
This is off our tips page maybe this will help you.

Put in one of these today. Book gives 8.5 took about 3 hrs. The 98 model is harder to do. I started by taking the hoses aloose. Then move the blower resister. Look down in there---unscrew a bolt going the firewall into the blower housing. There is a stud coming through the firewall in the middle. Takes 7/16 socket--take care of that one. Now go to the inside and take the whole dash and put it in the backseat. Scews at the top. A 10mm headed bolt on each side. Drop the column down. Need to do some unplugging. Remove glovebox and you got a big electrical connector-use 7mm socket. A vac. Connector. Get some slack going for the ant. Cable. IMPORTANT-- Take aloose one connector at bcm(plastic box in middle). The one at the top going to dash.I almost pulled it by the roots. After pulling the dash back a little you will see a connector on driver's side with big wires---get it. And get the ant. Cable out the back of radio. None of this bad to do. The housing has a 10mm headed bolt at bottom and two screws coming in backwards through the firewall. Undo the bolt. I used a hammer and big screwwdriver on the other two underthere. Yank back-do the core. I could do three of these in one day and I'm getting old. Didn't take pictures sorry. Got a late start on it today and to my surprise finished it. If you think this one is hard better run when a jeep comes in.
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Friday, February 5th, 2021 AT 9:37 AM (Merged)
Tiny
JERRY HOLMAN
  • MEMBER
  • 1 POST
  • 1999 GMC JIMMY
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 165,000 MILES
I am trying to replace heater core and have almost the whole dash taken apart - please help
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Friday, February 5th, 2021 AT 9:37 AM (Merged)
Tiny
SWILLIAMS
  • MECHANIC
  • 597 POSTS
You need to pull the entire dash panel all the way out. Not just the parts attached to it. You will find bolts behind the A/C vents, The speaker grilles, the defrost grill, and one on each end under the dash. Plus a couple in the middle as well. You also need to unbolt the steering column from the dash on the drivers side. Then pull the entire thing toward the drivers side. Now you will see the heater case attached to the firewall. Remove the screws holding it (including the two that come through from the engine side) and you will find the core. Remove the core and clean out the mounting area. Install the new core and then test the doors and controls for operation before you button it all back together. Nothing like replacing the core and finding out you disconnected the heat bypass door!
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Friday, February 5th, 2021 AT 9:37 AM (Merged)
Tiny
MATTYB123
  • MEMBER
  • 1 POST
  • 1997 GMC JIMMY
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 17,000 MILES
What steps do I take to change the heater core
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Friday, February 5th, 2021 AT 9:38 AM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Figure 41: Heater Assembly Component View


https://www.2carpros.com/forum/automotive_pictures/12900_hc_11.jpg



HEATER CORE REPLACEMENT

Remove Or Disconnect
1.Engine coolant.
2.Heater hoses.
*Refer to "Heater Hose". See: Heater Hose Replacement
3.Instrument panel.
*Refer to "Dash Board" under Body and Frame / Interior Trim. See: Body and FrameInterior Moulding / TrimDashboard / Instrument Panel
4.Rear case screws. (88)
5.Rear case. (96)
6.Screws. (94)
7.Straps. (93)
8.Heater core. (92)
9.Seals. (89 & 90)

Install Or Connect
1.Seals. (89 & 90)
2.Heater core. (92)
3.Straps. (93)
4.Screws. (94)
5.Rear case. (96)
6.Rear case screws. (88)
7.Instrument panel.
8.Heater hoses.
9.Engine coolant.

*Check the system for leaks.
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Friday, February 5th, 2021 AT 9:38 AM (Merged)
Tiny
PAMAROSE
  • MEMBER
  • 1 POST
  • 1996 GMC JIMMY
  • 2,040 MILES
Want to remove heater core
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Friday, February 5th, 2021 AT 9:38 AM (Merged)
Tiny
FIXITMR
  • MECHANIC
  • 9,990 POSTS
The entire dash has to be removed. This is because the housing is too big to remove to access the heater core. In the engine compartement, drain coolant and remove heater hoses at the upper r/h side of firewall. Inside the vehicle you have to systematically remove all lower dash access panels. Undo the bolts holding the steering column and lower it. On each end of the dash there are torx bolts and regular bolts to be removed. There is one bolt approx below the vent that is right of center. Remove (on top of dash) speaker covers and heater grill, then remove bolts underneath. The dash should pivot back to access wire harnesses. Mark and undo connections, emergency brake cable and antenna cable. Once all the conections have been undone the dash can be removed through the passenger door. Amazing, now you can finally see the housing for the heater core. Remove the cover and then remove bolts holding in heater core. Intallation is reverse. I don't want to oversimplify this, lots of patience and time is required. Good luck
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Friday, February 5th, 2021 AT 9:38 AM (Merged)
Tiny
2CP-ARCHIVES
  • MEMBER
  • 4,540 POSTS
  • 1995 GMC JIMMY
  • 160 MILES
I recently changed the heater core & the car puts. Out heat, but after a few seconds the vent door closes. I can hold the switch and force it to stay open, but I am afraid to damage something. Is there a part that may be replaced to allow the vent door to stay open while heater is on?
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Friday, February 5th, 2021 AT 9:39 AM (Merged)
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
Are you talking about the actuator for the dash?
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Friday, February 5th, 2021 AT 9:39 AM (Merged)
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
Note the vacuum diagram for hvac. The actuator may be losing vacuum?
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Friday, February 5th, 2021 AT 9:39 AM (Merged)
Tiny
TNTRAMOS
  • MEMBER
  • 1 POST
  • GMC JIMMY
I have a 97 GMC Jimmy and the heater core is leaking on the floorboard. I have the dash mostly apart but I am now stuck and I can't get the dash completely removed to gain access. A friend of mine said I could just bypass the heater core and connect the water lines together. I live in Houston and I never use heat but I am afraid that if I bypass the core then other problems may arise. My questions are:
If I bypass the heater core -
Will the air conditioner still work?
Will hot air flow into the cab from the engine (Can I plug the core inlets to prevent)?
Will this have any overheating effects?
Are there other issues I should be aware of?

Thank you
Tony Ramos
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Friday, February 5th, 2021 AT 9:39 AM (Merged)
Tiny
SERVICE WRITER
  • MECHANIC
  • 9,123 POSTS
You can buy a brass nipple to splice the line together. It will not affect the a/c. The pipes going into the firewall can just be left alone. You can plug them with a piece of heater hose and a bolts clamped to it if you like. You should have no affect regarding overheating from doing this.
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Friday, February 5th, 2021 AT 9:39 AM (Merged)

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