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'88 C2500 leaks after heater core replacement

Discussion in 'General Chevy & GM Tech Questions' started by wl_walker, Oct 19, 2008.

  1. wl_walker

    wl_walker Rockstar

    Last winter I replaced the heater core in what is now my truck (inherited recently after my father died) and now the passenger side of the carpet gets soaked when it rains. I checked everything and can't for the life of me figure out what I did wrong! I guess it is possible that there is a rotted area under the windshield, but this truck has no rust anywhere! (Norhtern California is a relatively dry climate) Does anyone have advice?

    Thanks in advance!
    Will
    1988 Silverado C2500 (a work in progress)
  2. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    First off make sure its the heater core (it probably isnt but no use taking chances) pressurize the cooling system with the heater turned on and see if you get any moisture, if you find moisture check to see if it smells like antifreeze.
    The leak is probably at the bottom of the windshield or on the firewall seams (most common places), pull back the carpet on the passenger side, put a running hose on the roof with water running down the windshiled, and start looking up under the dash area and at the firewall with a flashlight. You might get a little better access if you pull out the glove box.
    When you find the leak dry it out real good and seal with RTV.
    Last edited: Oct 20, 2008
  3. btmac8w

    btmac8w Member

    If your truck is a dark color, you can also use some talcum powder to help find the leak. After you pull the carpet back, spread the powder all around the floorpan up high into the footwell. Run the water down the windshield as posted before and the powder will wash away where the leak is.
  4. wl_walker

    wl_walker Rockstar

    Great info, will try both tests. I'm hoping it is not a rot issue, those never seem to get fixed without a costly body repair. I'd rather spend such money on fun stuff like new carpet! Will have to wait on that until I get the leak fixed.

    Thanks again all,

    Will
  5. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    It's not uncommon for the windshield to leak around the bottom edge on that model/yr truck, if fixed in a timely manner you can avoid costly corrosion repairs. The bottom edge of the windshield has a habit of pulling away from the sealant.
  6. wl_walker

    wl_walker Rockstar

    So I would think that if the windshield has pulled up, replacing the windshield would fix the problem. Mine has a crack and I am insured for glass.
  7. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    Yep that could cure the problem.
    Before having the windshield replaced look around the cowl and under the dash to ensure you dont have corrosion issues. If you do have issues get the Ins. approval for the replacement glass, pull the windshield a day or two prior and repair the issues then have the glass installed.
  8. wl_walker

    wl_walker Rockstar

    OK, so here's the deal: there is a plate set in a recess on the cowel just above the 'chimmney' air intake for the heater/AC blower. This plate was glued at one time, but the glue has hardened with age and seperated, so the plate was just sitting there allowing rainwater to flow into the passenger compartment. All I had to do was use some ATV black to seal it up again and now I'm dry. The best part is that there is no rust at all! A nice cheap fix!

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