Caddy is home but without heat
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Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, Caddy is home but without heat in Past Cadillac Vehicle Discussion; Greetings My 2002 DHS is back home today after it's 10 day stay at the rebuilder's. In addition to the ...
  1. #1
    markmnj's Avatar
    markmnj is offline Cadillac Owners Fanatic
    Automobile(s): 1973 Cadillac Hearse, 2002 Cadillac DHS
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    Caddy is home but without heat

    Greetings

    My 2002 DHS is back home today after it's 10 day stay at the rebuilder's. In addition to the head gaskets and threads it's sporting a new timing kitm one new coil pack (had a flaky module), bottom end reseal with a new rear main seal. Basically everything that was leaking or could leak has been fixed. They also replaced the coolant fitting on the firewall side of the engine. He said something about the metal quick release was rusted and leaking

    However, I have no heat! If you bring the RPM up on the highway you can get a little warm air which goes cold again. Shop guys say they found evidence of sealer in the motor from a previous owner. They cleaned all of it out but some may have been dislodged from the process and found its way to the heater core. It was too hot to mess with down there and I wanted to bring it home. His suggestion was to let it cool, pull the heater hoses and blow shop air thru the core and see what comes out.

    Could the system have an air bubble trapped in the heater core?

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  3. #2
    basscatt's Avatar
    basscatt is online now Cadillac Owners Master
    Automobile(s): 89 Coupe DeVille, 95 Sedan DeVille, 03 SLS, two 02 DHS's
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    Re: Caddy is home but without heat

    check the PURGE LINE - for flow -
    that is the only way air gets purged from the cooling system -

    to verify coolant flow through the heater core -
    bring the engine to operating temp -

    set interior temp to 90 -
    set fan to highest speed -
    select the center vents -

    feel the heater hoses -

    they BOTH should be hot enough -
    that you wouldn't want to hold them very long -

    if there is a dramatic difference in the temperature of the two hoses -
    the heater core is likely blocked -

  4. #3
    markmnj's Avatar
    markmnj is offline Cadillac Owners Fanatic
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    Re: Caddy is home but without heat

    Cool, thanks. That's tomorrows job.

  5. #4
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: Caddy is home but without heat

    Quote Originally Posted by markmnj View Post
    Shop guys say they found evidence of sealer in the motor from a previous owner.
    Miracle-in-a-bottle strikes again.

  6. #5
    markmnj's Avatar
    markmnj is offline Cadillac Owners Fanatic
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    Re: Caddy is home but without heat

    Yes, looks like that. I figure some spray can mechanic/owner poured it in and traded it in and I bought it shortly after. I love the car though and have no regrets. I figure now that it's properly repaired I have a known set of values under the hood. Looking forward to driving it and spoiling it with care.

    Back to my heater issue. I checked the purge line as basscatt said and have a decent flow out of it. After it cools again I'm going to move onto pulling the hoses and giving the core a little reverse flow shop air. If it's old previously hardened sealer bits that got knocked loose perhaps it can't be too bad.

    Another question, Is it possible to have a misrouted heater hose? My alldata subscription doesn't show routing ins and outs for those. (Above 2000RPM I get warmish air. Cold again at lower engine speeds.)

  7. #6
    basscatt's Avatar
    basscatt is online now Cadillac Owners Master
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    Re: Caddy is home but without heat

    Quote Originally Posted by markmnj View Post
    Yes, looks like that. I figure some spray can mechanic/owner poured it in and traded it in and I bought it shortly after. I love the car though and have no regrets. I figure now that it's properly repaired I have a known set of values under the hood. Looking forward to driving it and spoiling it with care.

    Back to my heater issue. I checked the purge line as basscatt said and have a decent flow out of it. After it cools again I'm going to move onto pulling the hoses and giving the core a little reverse flow shop air. If it's old previously hardened sealer bits that got knocked loose perhaps it can't be too bad.

    Another question, Is it possible to have a misrouted heater hose? My alldata subscription doesn't show routing ins and outs for those. (Above 2000RPM I get warmish air. Cold again at lower engine speeds.)
    --------------------
    Is it possible to have a misrouted heater hose?
    doubtful -

    check the temperature of the heater hoses like I suggested above -

    one trick I used in the past with blocked heater cores -
    was to switch the 2 heater hoses at the core -
    this causes the coolant to flow in the opposite direction -
    and - over time - might break-up the clog -
    markmnj likes this.

  8. #7
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: Caddy is home but without heat

    I'd pull the hoses and hook up a garden hose to one and flush it with fresh water at line pressure. Then revers hoses and revers flush.
    basscatt likes this.

  9. #8
    markmnj's Avatar
    markmnj is offline Cadillac Owners Fanatic
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    Re: Caddy is home but without heat

    I have heat! Thanks for the help But to add a little confusion, I didn't notice anything out of the ordinary flowing from the core though. After blowing out with air and refilling everything works nicely. Perhaps it had an air bubble or a clog that dissolved as it came out. BTW I like that idea of reversing the hoses at the heater core. I'll be remembering that trick should I encounter a heater core issue on a vehicle.

  10. #9
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: Caddy is home but without heat

    The problem with reversing the hoses is that whatever was in the core just gets flushed back into the system and eventually works it's way back into the core again. You're far better off connecting a garden hose and flushing any crap out of the core and out of the engine.

  11. #10
    markmnj's Avatar
    markmnj is offline Cadillac Owners Fanatic
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    Re: Caddy is home but without heat

    I have a little more detail on what I did that got the heater core flowing again. I used air first, then water then a final dose of air to get all of the water out before pushing some fresh coolant in. Flushed/cleaned in reverse but hoses are hooked up as they were before. I sent a regulated 30 PSI through the system to play things safe.

    When I first applied the air I got a little coolant out followed by an unexpected shotgun blast that sent something flying out across the room and bathed me and my garage in Dex. I think that "something" may have been the problem. Since it was expelled in an aerosol fashion I could not find it to confirm.

  12. #11
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: Caddy is home but without heat

    Quote Originally Posted by markmnj View Post
    When I first applied the air I got a little coolant out followed by an unexpected shotgun blast that sent something flying out across the room and bathed me and my garage in Dex. I think that "something" may have been the problem.
    I would almost bet on it.

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