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Thread: heater core

  1. #1
    Junior Member
    Join Date
    Dec 2010

    Unhappy heater core

    I have a 1995 chevy C2500 truck and need to replace the heater core. I understand it is a nightmare. Can anyone give me some detailed info on where to start and exactly what I need to remove to get to the core?

    Thanks, Nextlevel

  2. #2
    Senior Member
    Join Date
    Dec 2007
    Heater core Have a read through this link.

  3. #3
    Junior Member
    Join Date
    Dec 2010
    greers ferry,ar
    i've just replaced mine and it was a witch. Is it leaking in the floor board? If not, you can blow it out by disconnecting both hoses, as far from the heater core as you can. Then just blow through the hose to backwash the trash, may need a air hose, but don't give that much pressure at first it will blow out. I replaced mine to find out all i had to do was blow it out.Then would recommend a good flushing of the whole system.

  4. #4
    Senior Member 87c10slammer's Avatar
    Join Date
    Mar 2008
    levittown pa
    accually its fairly easy compaired to some of the ones i have done.. it took about 30 mins on my 92 k1500 blazer.. the worst part is bending over backwards trying to get the screws out.

  5. #5
    Junior Member
    Join Date
    Dec 2010
    Yes it is leaking into the floor. These trucks changed mid year into a dashboard nightmare. According to the book you have to take out the steering column and take the one piece dash out. You also have to empty the freon out and take the evaporator loose because the evaporator and core are in the same big plastic box.

  6. #6
    Senior Member Saugeen Drifter's Avatar
    Join Date
    Jul 2009
    Port Elgin, Ontario, Canada
    It depends what kind of work you are willing to do. The heater core and radiator core are separate items so don't drain the AC lines. I apologize if first for the length of this and second if my explanation is too simplified for you, I have no idea of your mechanical knowledge, but here is a step by step that will have you filling the system back up in an hour.

    trucks applicable to;
    GM pick ups 89-98 this includes Silverado, Sierra, Cheyenne (maybe Blazer, S10, Tahoe, Yukon but unsure). I performed it on my 1989 Sierra SLE and found my 91 Silverado to be the same. Both of my trucks have A/C and are 350 CI.

    According to most posts I have read this is a lengthy nightmarish task to only be taken on my skilled professionals. Some say buy a manual, it could take up to 5 hrs or better, could involve dash removal, electrical manipulation, steering column removal, I even read in one post that told me you had to remove the radio antennae. I have found a way to remove and replace the heater core in less than 1 hr.

    Tools required;
    1/4 inch drive ratchet
    3 inch 1/4 drive extension
    7mm short socket
    philips screw driver
    socket for removal of hose clamps inside of engine compartment (sizes vary)
    1 sturdy razor blade knife
    1 towel (to lie on and avoid contact with asbestos heat shielding)
    Needle nose vise grips (2 pair)
    1 pair of regular vise grips (might need)
    fluid catch container

    Steps for removal:
    NOTE: before removing hoses label which hose goes where or to which tube.
    1- trace heater core hoses and pinch them off with the needle nose pliers about 6 inches from where they go in to the firewall, make sure not to pinch too much hose or you will damage the hoses. What you are trying to accomplish is pushing the interior of the hose material together in order to plug it off, thus stopping a mess and stopping the system from emptying fluid out.
    2- Place catch container of floor
    3- remove hose clamps from heater core ensuring the fluid falls in to the fluid catch container, if your catch all is clean enough you can reuse the fluid
    4- remove door sill plate on passenger side (plastic/steel plate you step on or over to get in to the passenger side of the vehicle), it should have 3 self taping screws holding it with Philips heads. If the Philips (star) heads are stripped or too corroded to get off, you can get them off from below the vehicle with the vise grips. A self tapping screw is a screw with an end that looks like a drill bit that drills its own hole before it pulls itself in.
    5- pull off the interior panel just forward of the passenger side door above the carpet, take note on how this came off and it will go back on just the same. Give it a good stiff pull towards the middle of the truck and it should pop off
    6- pull back and roll the floor carpet back and tuck it under the seats, which should be all the way back to maximize space for you to work
    7- lay a towel on the white cloth like material wrapped in clear plastic (this is an asbestos shield used as a heat shield because the exhaust runs right below it), avoid ripping the plastic wrap or disturbing it, asbestos is not harmful as long as it is not disturbed
    8 - now the screws for the cover plate. There are 6 of them, first 4 are in pairs of 2
    PAIR 1 -found beside the black duct facing the floor on the passenger side (remove 2)
    PAIR 2 - found midway towards the passenger door (remove 2)
    - NOTE: the bolt on the firewall is impossible to get off unless you do the following
    - cut the black insulation off the firewall using the razor blade knife
    - you will in no way be able to see this bolt, only feel it, so remove as much insulation as needed
    SINGLE 1 - found in the middle of the plastic that heads towards the firewall, you will see an indent in the plastic approximately 1 inch in diameter, inside the depression is the bolt
    SINGLE 2 - found on the side that runs parallel with the passenger side door
    9 - towards the firewall where you had removed bolt (single 1) you will notice the plastic cover runs to the firewall, remove the insulation around the plastic with the razor knife.
    10 - pull the cover off towards the floor
    11 - there is one more 7mm bolt to remove, using a mirror reflect the heater core to your eyesight, the bolt holds the heater core to the assembly
    12- now that all the bolts are out, the covers off, and the supporting bolt is off the heater core will pull right at you.

    Note 1: reverse all steps for installation
    Note 2: I found it impossible at first to get the cover back on, however after pulling the heater core towards me 1/2 an inch, the plastic fell in to place
    Note 3: the cover is made of plastic so do not over tighten and crack cover

    My time for removal and installation 45 minutes, but save yourself the hassle and put new bolts down to hold your door sill plate
    Cheers all Saugeen and Happy New Year

  7. #7
    Junior Member
    Join Date
    Dec 2010
    Thanks for your explanation. I appreciate simplicity. I am fairly good at mechanics and work on all my vehicles. I will see about your way of doing this today. I don't have carpet so I will not pull up the sill plate. Thanks again for your reply.


  8. #8
    Junior Member
    Join Date
    Dec 2010
    Well, I did get to the heater core but it is not like the one described above. It had 8 screws with a 5.5mm head. The hoses connect to the core on the engine side of the firewall. AFter all of this it was not the heater core. It was the bottom hose that was leaking past the clamp and squirting into the firewall and into the air plenum. How about that! At least I do not have to buy a new core.


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