1999 Deville overheating ?
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  • 1 Post By basscatt
Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, 1999 Deville overheating ? in Past Cadillac Vehicle Discussion; Hi, new here, trying to find info on overheating '99 Deville 4.6L. Anyone that can give direct links to pages ...
  1. #1
    cadgeorge is offline Cadillac Owners Member
    Automobile(s): 1999 Deville
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    1999 Deville overheating ?

    Hi, new here, trying to find info on overheating '99 Deville 4.6L.
    Anyone that can give direct links to pages discussing this problem with this car I would be greatful. The radiator fans seem to run intermittently, I hear them kick on sometimes, but when it was overheating the last time I shined a flash light down there and neither were running. I've read many things on many sights and there does not seem to be any real answers. I see headgaskets all the time but I also see many posts of people who say they did that and it still overheats. I put a new presurized overflow reservoir because I saw a tiny crack near the small hose but that did nothing to stop overheating. I see many say they replaced gaskets replaced pumps replaced thermostats replaced this replaced all those things and it still overheats. Is there any real answers to be found for this car. Or should I just pull out the .458 and put an end to this thing?

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  3. #2
    orconn's Avatar
    orconn is offline Cadillac Owners 10000+ Posts
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    Re: intro

    Welcome to the Forums, George! I am sure some one will come along shortly to the right forum to find answers to you Cad's problem. By the way, where are you from? Do you do your own mechanical work or do you depend on professional repair help?

  4. #3
    basscatt's Avatar
    basscatt is offline Cadillac Owners Master
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    Re: intro

    Quote Originally Posted by orconn View Post
    Welcome to the Forums, George! I am sure some one will come along shortly to the right forum to find answers to you Cad's problem. By the way, where are you from? Do you do your own mechanical work or do you depend on professional repair help?
    =====================
    here is the Deville specific forum -
    http://cadillacforums.com/forums/cad...ncluding-1985/

    and here is the Northstar motor forum -
    http://www.cadillacforums.com/forums...al-discussion/

    the quick answer is -

    FIRST - check the PURGE LINE -

    the PURGE LINE is the only way of expelling air from the Northstar cooling system -

    it is a 3/8 diameter hose that goes from a hollow bolt in the thermostat/waterpump housing area of the engine - and plugs onto a nipple on the side of the SERGE TANK -

    with the engine running - there should be a gentle - constant flow of coolant - from the engine - to the serge tank -

    if there is no flow - the most likely cause is a blockage in the hollow bolt -

    follow the hose towards the engine - with the engine OFF - remove the hose - use a straightened metal coat hanger - or something similar - and poke it into the hollow bolt -

    the coat hanger should go in about 2 1/2 inches -

    once the hollow bolt is cleared - you can briefly start the engine to verify coolant flow - be sure to use some sort of container to catch the coolant so you don't make a mess -

    check the hose and serge tank for blockage -

    ---------------------

    for kicks - check for Diagnostic Trouble Codes -

    if you don't know how - go here and read the ENTIRE post -

    http://www.cadillacforums.com/forums...odes-dtcs.html

    if you have any codes - post them here -
    ALONG WITH THEIR DEFINITIONS -

    --------------------------------

    to verify the worst suspicions -
    do a BLOCK TEST -
    the DEFINITIVE test for failed head gaskets in the Northstar motor -
    carnut likes this.

  5. #4
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: intro



    I hate to say it, but being a '99 does not put the odds in your favor.

  6. #5
    carnut is offline Cadillac Owners Master
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    Re: 1999 Deville overheating ?

    And what do you call overheating? True overheating means the coolant boils in the holding tank. If its running too hot, that's another discussion.

  7. #6
    SGWORLDWIDE's Avatar
    SGWORLDWIDE is offline Cadillac Owners Enthusiast
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    Quote Originally Posted by Ranger View Post


    I hate to say it, but being a '99 does not put the odds in your favor.
    I'm with ranger on that as well check the line if its clear then do a block test but on 99s that over heat its usually the worst scenario

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